1 Introduction to NURBS

1 Introduction to NURBS

Primitives

This chapter introduces you to NURBS primitive objects. There are several ways you can use NURBS primitives to build objects quickly and easily. Use primitives as a starting point, then use a combination of object and surface editing operations to complete a task.

Throughout this book you'll find examples where primitives are used as the base element of a particular task in combination with many of the Maya editing and creation operations.

NURBS Primitives CV Curve Tool EP Curve Tool Pencil Curve Tool Arc Tools Text Construction Plane Locator

Using NURBS primitives The most basic object type is the primitive. Primitives are pure shapes that can be used as the basis of creating more complex models. You can create five NURBS surfaces-Sphere, Cone, Cylinder, Cube, Plane, and Torus. You can also create a Circle and Square primitive.

Creating objects with NURBS primitives

You can instantly make simple NURBS objects like spheres, cubes, cylinders, cones, planes, and circles. When you select the NURBS primitive from the menu, it displays in all views at the origin of the grid (or ground plane).

By combining, transforming, trimming and cutting, or using surface functions, such as filleting, on these simple shapes, you can construct more complex objects.

Modifying primitives to build objects

There's a fast and easy way to do almost anything in Maya, but using simple primitive shapes and the transformation tools Maya provides is the easiest way to build something that is simple, but essential to a scene.

For example, you can use a NURBS primitive cube to build a staircase. You simply scale it, duplicate it, and move each step into place.

Or you can select surface curves (isoparms) on two spheres, create a fillet blend between them, and scale the spheres to create a bottle using a free-form surface fillet (Surfaces>Freeform Fillet).

To create a simple animation, you can also select surface CVs, transform them, and set key frames to the transformations.

First, select the CV or CVs you want to transform. Place the pointer over the active object, then with the right mouse button select Control Vertex from the marking menu.

In this example, one CV of a NURBS primitive sphere is selected and moved using the Move Tool.

You can also transform either one or multiple CVs from the Channel Box. Select the CV or CVs, then enter values in the X, Y and Z boxes provided.

The following shows the editable CV boxes in the Channel Box for a single CV. The X value is changed and the CV is moved accordingly.

In the next example, multiple CVs are moved from the Channel Box.

You can then animate the CVs by setting keyframes.

Important Note

You cannot animate CVs on an object that was created with history and then delete the object's history. The CV animation will not be correct and unexpected results will occur.

Using the Show Manipulator Tool with primitives

When you create a Sphere, Cone, or Cylinder NURBS primitive, you can display manipulators with which you can edit specific parameters of the primitive.

To display these manipulators, make sure the primitive is created with history. Select the Show Manipulator Tool while it is active (or before you create it), then click the primitive's heading in the Channel Box. You can also select the primitive's heading from the History menu in the Status Line or from the Inputs menu in the marking menu.

Editing primitives using revolve manipulators

The NURBS Sphere, Cylinder, and Cone primitives are like revolved surfaces, therefore the manipulators that display are revolve manipulators.

Circle Sweep manipulator

The circle at the bottom of the revolve manipulator is called the Circle Sweep manipulator. Click-drag the manipulator handle to sweep the sphere, or enter values in the Numerical Input line or the Channel Box. You can also enter a new Sweep value in the options window before you create the sphere, or from the Attribute Editor after you create the sphere.

AxisStartPoint and AxisEndPoint manipulators

The arrow manipulator handles represent the origin and direction of the axis: AxisStartPoint and AxisEndPoint. Click-drag these handles to reposition the axes. You can also enter values in the Numerical Input line while a manipulator is active or in the Location Attributes section of the sphere's Attribute Editor.

axisMidPoint manipulator

The axisMidPoint handle represents the pivot point position. Click-drag the middle handle, or enter values in the Numerical Input line or in the Attribute Editor.

NURBS primitives NURBS primitives are available from the Modeling menu set by selecting Create > NURBS Primitves.

Since most of the options for primitives are similar, the option descriptions for the Sphere NURBS primitive are described in detail. Descriptions of specific and unique characteristics of the other primitve types follow afterward.

Sphere

To set primitive options:

1 Select the type of primitive you want to create and click the box ( ) from the menu to open the options window (Create > NURBS Primitives > Sphere - ).

2 To change the option settings, immediately after the primitive is created, select Edit > Undo. Change the options, then press the Create button to create a new primitive.

Setting the default pivot point

Pivot

By default, the Pivot is set to Object, and the resulting primitive is created at the origin. The primitive appears centered about the specified pivot; the rotate and scale pivots of the primitive are at the origin.

For example, Sphere, Cone, and Cylinder primitives are revolved from simple hidden curves and this option defines the start point of the axis of revolution.

If you set Pivot to User Defined, you can enter values in the Pivot Point X, Y, and Z boxes to reposition the primitive. The resulting primitive is centered about this point.

Changing the direction of the X, Y, and Z axes

Axis

Select X, Y, or Z (Y is the default) to change the axis direction of the object. Select Free to enable the X, Y and Z Axis Definition boxes. Enter new values to

change the axis direction in X, Y and Z. Select Active View to place the object perpendicular to the current orthographic

view.

Note

The Active View option has no effect when the current modeling view is a camera or perspective view.

Changing the sweep angle

Start and End Sweep Angles

Enter the degree of rotation about the vertical world axis. Degree values can range from 0.00 to 360.00 degrees. The default is 360.00 degrees, which creates a full 360 degree of revolution. The following example shows the top view of a sphere after changing the End Sweep Angle to 180 degrees (a hemisphere).

See also "Editing primitives using revolve manipulators" on page 34 for information about the Circle Sweep manipulator.

Changing the radius value

Radius

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Enter a value in the Radius box or use the slider to change the radius.

Changing the surface degree

Surface Degree

Select a Surface Degree option to automatically create the NURBS sphere as a Linear (degree 1) or a Cubic (degree 3) B-spline. The default is Cubic.

Controlling the accuracy of the sphere using tolerance

The more sections and spans, the better the match. When you create a NURBS Sphere primitive, the sphere is always an approximation to a true sphere. In some cases you may want to build a surface that matches a true sphere to a certain tolerance. When you specify the tolerance, Number of Spans is automatically computed to be enough to be able to match a true sphere to the given tolerance.

Use Tolerance

If Use Tolerance is toggled on, you can see the effects when you change the values in the Tolerance slider from the Attribute Editor. Set this tolerance value in the options window before you create the sphere only if you know the values you need.

If set to None, no tolerance calculations are performed and the sphere is created with the given number of sections and spans. This is the default.

If set to Local, the following is displayed:

You can enter a new value to override the Positional tolerance value you set in Options > General Preferences > Modeling.

Local tolerance is useful on a per-task basis where you want to change these values, but don't want to change the Global tolerance values.

If set to Global tolerance, the Positional tolerance value you set inOptions > General Preferences > Modeling is used.

Subdividing the sphere

Number of Sections

The Number of Sections value specifies the number of subdivisions that are created on the sphere. The default value is 8. The following shows a sphere with 16 sections. A value less than 4 gives a poor approximation to a sphere.

You can also change the number of sections in the Channel Box or the Attribute Editor.

In the Channel Box, click the makeNurbSphere heading and enter a new value in the Sections box.

In the Attribute Editor, click the makeNurbSphere tab to open the Sphere History section of the editor, then enter a new value in the Sections box.

Changing the number of spans

Number of Spans

Enter a value in the Number of Spans box to increase the number of spans that define a primitive. A value less than 4 gives a poor approximation to a sphere.

You can also change the number of spans in the Channel Box or the Attribute Editor.

In the Channel Box, click the makeNurbSphere heading and enter a new value in the Spans box. In the Attribute Editor, click the makeNurbSphere tab to open the Sphere History section of the editor, then enter a new value in the Spans box.

Cube

Select NURBS > Create Primitives > Cube- to open the options window.

A NURBS Cube primitive consists of six separate sides. You can click to select a side of the cube in the view, or click on a heading in the Outliner or Hypergraph window (Window > Outliner or Hypergraph).

To select the cube as a whole object, select the top heading in the Outliner or Hypergraph window, or click the Select by hierarchy and combinations icon from the Status Line.

Changing the cube's width

Width

Enter a value in the Width box to change the default value or use the slider to change the width of the cube.

Changing the length and height ratios

Ratio of Length to Width / Height to Width

Enter a value in the Ratio of Length to Width or Height boxes to change the default value, or use the slider to specify the height and length of the cube.

Setting U and V patches

U patches/V Patches

Change the value in the U Patches or V Patches boxes or use the slider to set the number of (U, V) patches between the edges that make up the cube. This value changes the number of spans on an object. You can also change these values in the Channel Box or the Attribute Editor.

Cylinder

The NURBS Cylinder primitive is created as an open-ended cylinder, and may be created with or without end caps.

Changing the height to radius ratio

Ratio of Height to Radius

Use the slider or enter a new value in the Ratio of Height to Radius box to change the height to radius ratio of the cylinder.

Caps

Caps may be created for either or both ends of the cylinder, or not at all. In addition, caps may be created as degenerate surfaces (they are treated as part of the cylinder shape node), or with a separate transform node, so that they can be manipulated independently. The following illustration shows two cylinders with caps represented in the Hypergraph; the left one was created without the Extra Transforms option, and the right one with this option on.

Cone

The NURBS Cone primitive is created as a cone which may or not have a cap on its open end, similar to the NURBS cylinder's caps options.

Plane

The plane is a planar surface made up of a specified number of patches Change the value in the U Patches or V Patches boxes or use the slider to set the number of (U, V) patches between the edges that make up the plane. This value changes the number of spans on an object. You can also change these values in the Channel Box or the Attribute Editor.

Changing the length ratio

Ratio of Length to Width

Enter a value in the Ratio of Length to Width box to change the default value, or use the slider to specify the length of the plane. You can also change these values in the Channel Box or the Attribute Editor.

Common option descriptions

For information on the other options, refer to the following table.

Option Heading and page

Pivot "Setting the default pivot point" on page 37 Axis "Changing the direction of the X, Y, and Z axes" on page 37Width "Changing the cube's width" on page 42Surface Degree "Changing the surface degree" on page 38U/V Patches "Setting U and V patches" on page 43

Torus

A NURBS torus is a shape which is periodic along two axes.

Using the Torus primitive

Primitives are simple shapes which can be assembled and edited to create objects quickly and intuitively. The torus shape is useful as the basis of ring-shaped objects.

The torus primitive is created by selecting Create> NURBS Primitives > Torus.

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The torus primitive behaves in all other respects as other NURBS primitive modeling objects, sharing similar options.

Circle

The NURBS circle is a closed curve with options similar to the NURBS sphere primitive.

Square

The square primitive is a companion to the circle primitive.

Using the square primitive

The square primitive provides a rectangular set of NURBS curves which can be particularly useful when creating curves for use with architectural and planar shapes.

Note

The square primitive consists of four separate curves and is not a single shape.

Creating curves Since curve creation methods are tools, first adjust the option settings in the options window for the tool before you create the curves. If you create the curves with the default option settings, you can later edit the completed curve in the Attribute Editor.

The following topics are described in this chapter:

"Creating curves with CVs" on page 48 "Creating curves with edit points" on page 56 "Creating curves using a pencil" on page 60

Creating curves with CVs




A CV is a point that controls the shape of a curve or surface. Use the CV Curve Tool to create free-form curves. You can manipulate CVs using transformation tools to give localized, predictable modifications to your curves and surfaces.

Tip

Remember, more CVs doesn't necessarily mean easier control. You should try to keep the number of isoparms to a minimum.

Before you begin

When you construct a curve with CVs, you must place several points to complete the curve, depending on the curve degree setting in the options window. The following example uses the default curve degree of Cubic, degree 3. Since you need one point more than the curve degree, you have to place at least four points to construct the curve. See "About curve degrees" on page 53 for more information.

To create a curve with CVs:

1 Select Create > CV Curve Tool.

2 Position the pointer in any of the views where you want the curve to begin.

3 Click to place the first CV. The first CV is displayed as a small hollow box that indicates the start point of the curve.

Tip

If you hold the mouse button while you click, the CV can be dragged to any location in the view. Release the mouse button to place the CV.

4 Click where you want to place the second CV. This CV is displayed as a small letter u. Once you place the CV, a line joins the two CVs. This is the hull line. The hull line is part of the control polygon and does not represent a curve or curve segment.

5 Click to place a third CV. Another hull line is created to connect the second and third CVs. The curve is not built yet since this is a degree 3 curve (Cubic by default) and you have to place at least four points.

6 Click to place the last and fourth CV. When you place the fourth CV, a curve segment is created that interpolates the first and last CVs.


As you continue to place CVs, new curve segments are created and the curve continually updates to interpolate the last CV placed.

Tip

To complete the curve so you can start to place new curve points, press Enter.

To create a CV curve-on-surface:

1 Select the NURBS surface.

2 Click the Make Live icon on the Status Line (or select Modify > Make Live) to make the surface live.

3 Select Curves>CV Curve Tool and place the curve-on-surface CVs directly on the live surface.

Changing the CV curve shape

Once a CV curve is drawn, or while you are drawing it, you may want to modify its shape. You can use the transformation tools to move, rotate, or scale CVs to change the shape of your curves.

To change the shape of the curve as you create it:

1

Before you press Enter to complete the CV curve, press the Insert key on the keyboard. This displays a move manipulator, which appears on the CV at the end of the curve by default.

2 Drag the manipulator to move the CV and to change the curve's shape.

3 To continue to change the curve's shape, click with the left mouse button to select another CV and drag the manipulator.

Tip

You can marquee-select more than one CV at a time. Remember to press the Insert key to continue placing CVs.

To change the shape of the curve after it is constructed:

1

Click the Select by component type icon from the Status Line. 2

Click the Points icon, press the right mouse button to display the pop-up menu, then toggle CVs on.

or While the pointer is over an active CV curve, use the right mouse button and drag to select Control Vertex from the marking menu.

3 Click to select the CV (or CVs) you want to move.

4 Select a transformation tool, (in this example, the Move Tool), and drag the manipulator to move the CV.

Setting CV Curve Tool options

Set the tool options before you create the curve. To open the options window, select Create > CV Curve Tool - .

To change the options after the curve is created, use the Channel Box or the Attribute Editor. See for details.

Changing the curve degree

Select a Curve Degree option to specify the curve degree.

1 Linear curves are often referred to as polylines (linear segments), degree 2 curves as quadratics, degree 3 Cubic curves as cubics (the default), degree 5 as quintic, and degree 7 as heptic. The higher the curve degree, the more points you need to define a single curve span. If the number of control points is the same and the curve degree is high, the curve looks as though it has more tension than if the degree is low.

About curve degrees

Each curve segment is defined and controlled by n+1 CVs, where n is the degree of the curve.

For example, a curve of degree 5 requires 6 CVs to form a curve segment.

A curve of degree 7 requires 8 CVs.

Changing the knot spacing

The type of knot spacing relates to the U parameter values assigned to CVs (also referred to as parameterization). Select an option for Knot Spacing.

Chord length

If you create a curve with Chord length knot spacing, the parameter value depends on the distance along the length of the curve. An initial parameter value of 0 is assigned to the start of the curve, then the value is increased proportionally to the chord length between edit points.

Uniform

If you create a curve with Uniform knot spacing, the parameters have equally spaced values (0, 1, 2, and so on) between edit points. The parameter values of a uniform curve always range from 0 to the total number of spans on the curve. This is the default setting.

Tip

Uniform knot spacing produces a curve with a more predictable parameterization. Chord knot spacing produces a better curvature distribution, and, when used to build surfaces, better texture mapping. See for more information about knot spacing.

Multiple End Knots

The joints where the curve spans are joined are called knots. Toggle Multiple End Knots on to help control the shape of the curve. The default is on.

Creating curves with edit points An edit point is a point that controls the shape of a curve or surface. Use the EP Curve Tool to help define how many spans sit on the curve. Edit point curves are also useful if the curve must go through certain points.

When constructing a curve with edit points, the edit points are visible while the curve is being constructed. Unlike the CV method where you must place several points to construct the curve, only two edit points are necessary to create the initial curve segment, no matter what degree of curve.

To create an edit point curve:

1 Select Create > EP Curve Tool.

2 Click in any of the views to place the first edit point. A small letter x is displayed.

3 Click to place the second edit point. When you place the second edit point, you create a curve segment that interpolates the two edit points. Click to place as many edit points as you want. As you plot each additional edit point, a new curve segment is created.

4 To complete the curve so you can start to place new curve points, press Enter. The following shows a curve constructed with four edit points.

To create an edit point curve-on-surface:

1 Select the NURBS surface.

2 Click the Make Live icon on the Status Line (or select Modify > Make Live) to make the surface live.

3 Select Create > EP Curve Tool and place the curve-on-surface points directly on the live surface.

Changing the edit point curve shape

Once an edit point curve is drawn, or while you are drawing it, you may want to modify its shape.You can use the transformation tools to move, rotate, or scale edit points to change the shape of your curves.

To change the shape of the curve as you create it:

1 Before you complete the edit point curve, press the Insert key on the keyboard. This displays a move manipulator which appears on the edit point at the end of the curve by default.

2 Drag the manipulator to change the curve's shape.

3 To continue to change the curve's shape, click with the left mouse button to select another edit point and drag the manipulator.

Notes

You can only select one edit point at a time. This prevents the curve shape from changing too much.

To change the shape of the curve after it is constructed:

1 Click the Select by component type icon.

2 Click the Parm Points icon to display the pop-up menu, then toggle Edit Points on.

or While the pointer is over an active edit point curve, use the right mouse button and drag to select Edit Point from the marking menu.

3 Click to select the edit point (or edit points) you want to move. Select a transformation tool (for example, the Move Tool), and drag the manipulator to move the edit point.

Setting EP Curve Tool options

Set the tool options before you create the curve. To open the options window, select Create > EP Curve Tool - .



Select a Curve Degree option to specify the curve degree.

1 Linear curves are often referred to as polylines (linear segments), degree 2 curves as quadratics, 3 Cubic curves as cubics (the default), degree 5 as quintic, and degree 7 as heptic. The higher the curve degree, the more points you need to define a single curve span. If the number of control points is the same and the curve degree is high, the curve looks as though it has more tension than if the degree is low.

Changing the knot spacing

The type of knot spacing relates to the U parameter values assigned to edit points (also referred to as parameterization). Select an option for Knot Spacing.

Chord length

If you create a curve with Chord length knot spacing, the parameter value depends on the distance along the length of the curve. An initial parameter value of 0 is assigned to the start of the curve, then the value is increased proportionally to the chord length between edit points.

Uniform

If you create a curve with Uniform knot spacing, the parameters have equally spaced values (0, 1, 2, and so on) between edit points. The parameter values of a uniform curve always range from 0 to the total number of spans on the curve. This is the default setting.

Tip

Uniform knot spacing produces a curve with a more predictable parameterization. Chord knot spacing produces a better curvature distribution, and, when used to build surfaces, better texture mapping.

Creating curves using a pencil Use th Create > Pencil Curve Tool to sketch a curve, rather than create it by placing CVs or edit points.

To create a curve using a pencil:

Sometimes the most natural way to create a curve is to sketch it, rather than placing CVs or edit points. The pencil construction method lets you create a curve as easily as drawing a line on a piece of paper.

1 Select Create > Pencil Curve Tool.

2 The pointer changes to a small pencil. Position it where you want the curve to begin.

3 Click-drag the pencil to sketch a curve.

4 To stop sketching, release the mouse button. The line is fit with a curve that has chord length parameterization by default.

Sketching in different views

As the curve is sketched, the pencil position is sampled as often as possible. Points are kept if they are at least five screen pixels from the previous point. When the mouse button is released and the actual curve is fitted to the points, the curve interpolates the first and last point.

If you are sketching in an orthographic view (front, top, or side), two of the coordinates of the spline correspond to those of the current view and the other coordinate is set to 0. If sketching in the perspective view, the curve is created on the ground plane or live surface.

Setting Pencil Curve Tool options

Set the tool options before you create the curve. To open the options window, select Create > Pencil Curve Tool - .



Select a Curve Degree option to specify the curve degree. 1 Linear curves are often referred to as polylines (linear segments), and degree 3 curves as cubics.

Warning!

Curves created using a pencil usually have many CVs. Use Edit Curves > Rebuild Curves to smooth out and simplify this type of curve.

Arc Tools

Use the Arc Tools to create semi-circular NURBS curves by placing points which define the length and radius of the arc.

As long as construction history is maintained, a makeCircularArc node is available for editing the arc creation points in the Channel Box and Attribute Editor.

While creating an arc using the Arc Tools, it is possible to edit points already placed by clicking with the middle mouse button, which will allow you to reposition that control point.

The Arc Tools operate on the active view at all times, and will therefore always create arcs perpendicular to an orthographic view. When using a perspective or camera view to create an arc, the Arc Tool will generate the arc on the ground plane.

The Arc Tools provide numeric feedback as to the radius of the arc being created.

Note

You cannot create a circle with the arc tools, or have any of the points used to create the arc coincident.

Common Arc Tool options

The Two and Three Point Arc Tools share the same tool settings. Select Create > Arc Tools > Two Point Arc Tool - or Three Point Arc Tool - to open the tool settings window.

Geometry Options

Circular Arc Degree

Select linear or degree 3 curves to be generated with the tool.

Sections

Enter a number in the input field or use the slider to select the number of curve segments used to describe the arc.

3-Point Circular Arc

Use the Create > Arc Tools > Three Point Arc Tool to create an arc by placing successive points which define the start, arc radius, and end points of the arc.

2-Point Circular Arc

Use Create > Arc Tools > Two Point Arc Tool to create an arc by placing the start and end point of a arc. The resulting curve will have a radius which is half the distance between the two points.

Once the start and end points have been placed, the vector direction of the arc is shown as a blue square, and the arc toggle as a double-circle manipulator icon.

Click on the arc direction vector to move the arc's radius origin interactively. To use the Channel Box to view and edit by clicking on the makeTwoPointCircularArc node.

Click on the toggle arc manipulator icon to change the orientation across the axis of the created arc, or change the value in the Channel Box. Note that the arc will flip when you move the arc control points across the radius' axis.

Using a construction plane Use Create \> Construction Plane to create an infinite plane perpendicular to the Z axis, passing through the origin (the X Y plane, which is the default). This type of plane differs from a NURBS primitive plane because you cannot render or animate it. You use these planes as construction aids. By default, a construction plane is created as a 24 x 24 unit square.

You can use a construction plane as a live construction surface (click the Make Live icon on the Status Line or select Modify \> Make Live).

A live construction plane replaces the ground plane as the surface on which points are placed when using one of the curve creation tools, or on which objects are moved relative to. By transforming the plane, planar curves can be created in arbitrary planes.

Setting Construction Plane Options

Select Create \> Construction Plane - to open the options window.

Before you create a new construction plane, change the options, if necessary, then click the Apply button.

Creating a construction plane at a specified location

Pole Axis

The Pole Axis determines the orientation of the construction plane. The default is an YX plane.

Determining the size of the construction plane

Size

Enter a value in the Size box or use a slider to specify a size for the new construction plane.

Transforming the construction plane

You can use the transformation tools to move, scale, and rotate the construction plane. Since you cannot, however, select a live object, either:

transform the plane before you make it live, toggle the live plane off, select it and transform it, then make it live again

Editing the construction plane in the Attribute Editor

The Attribute Editor for a construction plane contains generic attributes you use to transform and alter the display of the plane. See for details.

Creating and editing text Use Create > Text to create text objects and control their characteristics. A wide selection of fonts are available.

To create text:

1 Select Create > Text.

2 The word Maya is displayed at the origin (0, 0, 0) by default.

To create your own text curves, open the options window, type the text you want to create, select a specific font, and the type of text you need. See the following for details.

Setting Create Text options

Select Create > Text - to open the options window.

Entering new text and changing the font

Text Curves options let you alter the text string in a number of ways. After you select your options, click the Create button to see the resulting text.

Tip

The options only affect the active text string in the text field. Text that has already been placed is not affected.

To change the text:

1 Select Create > Text - to open the options window.

2 Type a new word in the Text box.

3 Select the Font and set the Type options, then click the Create button.

To change the font and create the new text:

1 Click the arrow besideprent font from the menu.

2 Press the Create button. The new text appears at the origin in the font you selected.The following shows the word Magic in an AvantGarde-Book font.

Transforming text

The text that first appears at the origin when you select Create Text is active by default. Text are curves, which means they are separate entities. All the curves for one text string are grouped under one transform.The transform results can vary depending on the way you select the text.

To transform the text later (after you deselect the text then perform another operation and reselect it), you will find that the letters are not transformed together.

To transform a text string:

If you want to transform a whole string of existing text, the transformation will occur on each letter individually if you marquee-select the text. To transform the whole string, do the following:

1 Marquee-select the letters. Notice the headings in the Channel Box. The lead object, (the c in Magic), is the only curve that appears while the other letters are individual curves.

2 Change some of the values in the Channel Box. In this example, the X, Y, and Z Scale values are changed. Notice that all letters are scaled, but the space between the letters is lost.

To correct this problem, select Edit \> Undo, deselect the text, then change the selection type. Click the Select by hierarchy and combinations icon and reselect the text.

or 3

Open the Outliner window (Window \> Outliner) and select the top text object (Text_Magic_1).

4

The heading in the Channel Box now displays the text string as one object (Text_Magic_1), and all the letters are displayed in the lead object color.

5 You can now transform the whole string as one object.

To transform individual letters:

1 If you want to transform just one letter in a text string, open the Outliner window (Window \> Outliner).

2 The letters in a text string are grouped under a parent node called Text_Magic_1. Click the triangle beside this heading to display the individual letters and select the one you need. The Channel Box is updated and the letter is highlighted in the view.

Changing the text type

Type

The three Type buttons, Curves, Trim, and Poly, are used to create text in three different formats. Select one of these before you create the text.

The Curves text type is the default. The text is displayed as NURBS curves which you can transform and manipulate.

The Trim text type is created as planar trim surfaces. This means that these letters will render because they are surfaces.

The Poly text type is created as polygons which you can manipulate as you would any other polygonal entity. When this text type is selected, a planar trim curve is created between the curve and tessellate nodes, but you only see the polygonal surface, not the planar surface.

Notice the difference between a Trim text string and a Poly text string in the Hypergraph (Window \> Hypergraph).

Editing the text in the Attribute Editor

The Attribute Editor for text curves contains the same transform attributes as you would find for curves. See for details.

Curve Editing

this chapter includes

Add Points Tool Curve Editing Tool Project Tangent Rebuild CurveExtend Curve Extend Curve On Surface Insert Knot Attach Curves Detach Curves Align Curves Open/Close Curves Reverse Curves Cut Curves Intersect Curves CV Hardness Smooth Curve Offset Curve Duplicate Surface Curves Curve Fillet Fit B-Spline

Creating Surfaces

In this chapter you will learn how to create surfaces using various Maya construction methods.

This chapter includes the following topics:

Bevel Extrude Loft Planar Revolve Boundary Birail

Beveling surfaces Use Surfaces>Bevel to create an extruded surface with a beveled edge from any curve, including text curves and trim edges.

To create a beveled surface from a curve:

Click on the curve you want to bevel and select Surfaces \> Bevel. The following example shows a text curve beveled with the default options.

To create a beveled surface from an isoparm:

1 To select the isoparms, click the Select by component type icon from the Status Line.

2 With the right mouse button, click the Lines icon and toggle Isoparms on from the pop-up menu.

or While the pointer is positioned over the active surface, use the right mouse button to select Isoparm from the marking menu.

3 Click to select an isoparm.

4 Select Surfaces>Bevel to bevel the isoparm.

Note

By default, Bevel Width and Bevel Depth are 0.1 linear units of measure, and Extrude Height is 1.00 linear units of measure.

Changing the bevel's dimensions interactively

You can change the dimensions of the bevel interactively with the Show Manipulator Tool, or in the Numerical Input line. You can also enter values in the Channel Box or the Attribute Editor. Note that negative values are acceptable.

If you want to edit the beveled curve from the Channel Box or Attribute Editor, the manipulators do not have to be displayed.

Editing a beveled curve with manipulators

If you bevel a curve, the following manipulators are displayed when you click the Show Manipulator icon and click the bevel heading in the Channel Box.

To interactively edit the bevel units, click-drag the manipulator handles. The Feedback Line displays the current measurement of each bevel unit as you move an active manipulator. You can also enter values in the Numerical Input line or in the Channel Box.

Changing the bevel height

The HeightPoint manipulator handle corresponds to the Extrude Depth option in the Channel Box. To change the bevel height, click-drag the HeightPoint manipulator handle. You can also enter a value in the Numerical Input line or in the Extrude Depth box in the Channel Box.

Changing the bevel width

To change the bevel width, click-drag the WidthPoint manipulator handle. You can also enter a value in the Numerical Input line or in the Width box in the Channel Box.

Changing the bevel depth

To change the bevel depth, click-drag the DepthPoint manipulator handle. You can also enter a value in the Numerical Input line or in the Depth box in the Channel Box.

Reversing the bevel direction

To reverse the direction of the bevel, use a negative value for the bevel depth, width, and height (or Extrude Depth). Change these values in the Channel Box or in the options window.

The following shows a beveled isoparm created in the default direction, and one in the reverse direction. Sometimes, this is the result you may want. For instance, you may want to create a beveled edge on a surface as shown in the example.

Editing a beveled isoparm with manipulators

Although the same manipulators are displayed for a beveled isoparm, an additional set of manipulators, StartParam and EndParam, become available when you click the isoparm heading in the Channel Box.

Click-drag the start and end parameter manipulators to change the beveled isoparm segment. You can also enter values in the Numerical Input line or in the Min and Max boxes in the Channel Box. The following shows what happens when you edit the StartParam.

Setting Bevel options

Select Surfaces>Bevel - to open the options window.

Attaching the bevel surfaces

Attach Surfaces

Toggle Attach Surfaces on to attach each part of the bevel surface. The default is on. If toggled off, the surfaces are not attached.

For example, if Attach Surfaces is toggled off and you create a bevel with Bevel set to Both, three surfaces are created. These surfaces are independent and can be selected and modified as such.

You can select one of these surfaces from the Hypergraph or Outliner window (Window>Hypergraph or Outliner).

You can also select the surface you want to edit from the Objects pop-up menu in the Channel Box and open its Attribute Editor.

Selecting a bevel surface area

Bevel

The Bevel options specify whether the beveled surface area is applied to the top, bottom, or both sides of the original curve or isoparm. The following example uses a NURBS Circle primitive curve using each method.

Note

Selecting the Bevel Off option disables the bevel parameter controls (Width, Depth, Corners, and Cap Edge). Used in this way, Bevel may be used for simple extrusion purposes.

Changing the bevel dimensions from the options window

You can enter exact bevel dimensions values before the bevel is created.

Bevel Width

The Bevel Width value specifies the initial width of the bevel as viewed from the front of the curve or isoparm.

Bevel Depth

The Bevel Depth value specifies the initial depth of the bevel portion of the surface.

Tip

The combination of Bevel Width and Bevel Depth values determine the angle of the bevel.

Extrude Height

The Extrude Height value specifies the height of the extruded portion of the surface, not including the bevel surface area. For more information, see:

"Editing a beveled curve with manipulators" on page 306 "Editing a beveled isoparm with manipulators" on page 308 "Editing a beveled surface in the Attribute Editor" on page 316

Selecting a bevel corner type

Bevel Corners

The Bevel Corners options specify how corners in the original construction curves are handled in the beveled surface.

Note

If the curve is degree is 1 or 2, the bevel's surface will be cubic (degree 3).

Selecting bevel cap edges to determine the bevel shape

Bevel Cap Edge

The Bevel Cap Edge options are used to determine the shape of the beveled part of the surface.

http://caad.arch.ethz.ch/info/maya/manual/UserGuide/ModelingNURBS/modelNURBSsurfaces.fm1.html#170491



Setting the curve range

Use the Curve Range options if you are creating a bevel from a curve.

Curve Range

Select Complete to use the entire curve for the bevel operation. Complete is the default setting.

Select Partial to only use a segment of the curve for the bevel. When you select the Show Manipulator Tool, a manipulator is displayed at each end of the curve. Use these manipulators to edit a part of the input curve to change the beveled result.

Editing part of the beveled curve

Select Partial as the Curve Range in the options window and click the Show Manipulator icon to display the curve range manipulators and editable parameters in the Channel Box.

Click the subCurve heading in the Channel Box for the input curve you want to edit, then click-drag the StartParam or EndParam manipulator handles to interactively edit the input curve. You can also enter values in the Min and Max boxes.

You can adjust these subCurves in the Attribute Editor if you require further modifications. See "Editing a beveled surface in the Attribute Editor" on page 316, and "Editing a beveled isoparm with manipulators" on page 308 for more details.

Choosing the output geometry

Output Geometry

Select either Nurbs or Polygons for the output geometry type. NURBS surfaces are created by default. See for more information on the Polygons options.

Setting the bevel tolerance

Use Tolerance

The Use Tolerance options let you create a bevel within a specified tolerance of the original input curves. You can apply tolerance globally or locally.

Global tolerance means the Positional value you set in Options>General Preferences>Modeling is used.




If you select Local tolerance, you can enter a new value to override the Positional tolerance value you set in Modeling Preferences.

Local tolerance is useful if you want to change these values often, but don't want to change the Global tolerance all the time.

Editing a beveled surface in the Attribute Editor

To edit the completed beveled surface, use the Attribute Editor. To open the Attribute Editor, either:

Click the option box ( ) in the Object pop-up menu in the Channel Box. Click the option box ( ) in the History list menu on the Status Line. Click the option box ( ) in the Inputs pop-up menu in the marking menu. Select Window>Attribute Editor.

The options you set in the options window or the Channel Box are displayed. See"Changing the bevel's dimensions interactively" on page 305 and "Setting Bevel options" on page 309 for details.

Input Curve

The Input Curve information is read-only. It gives you access to the history of the curves or isoparms you used to create the bevel surface. Click the arrow buttons to select the curve and open its section of the editor.

Editing the subCurves in the Attribute Editor

If you set the Curve Range to Partial in the options window when the bevel was created, you have access to the Attribute Editor for the resulting subCurves. See in for details.




Extruding surfaces Use Surfaces>Extrude to construct a surface by moving a cross sectional profile curve along a path. Extrude works by sweeping a profile curve. Before you extrude, set the pivot point of each profile curve to specify the relationship between the profile and the path.

The profile curve, the curve you want to extrude along the path, can be an open or closed free curve. You can also use a surface isoparm, curve-on-surface, or a trim boundary.

To create an extruded surface:

You need at least two curves to create an extruded surface: a path curve and a profile curve. The profile curve is the curve that gets swept along the path curve to create the surface. The path curve is the last selected curve.

1 Select the profile curve first, then Shift-select the path curve. The last curve you select (the path curve) displays in the selected default green color.

2 Select Surfaces>Extrude.

Tip

If you select more than two curves, select all the profile curves first, then select the path curve last.

To extrude a profile curve without using a path curve, change the extrude Style to Distance in the options window. See "Choosing the extrude style" on page 319 for details.


Restrictions

If the extrusion path has sudden changes of direction, undesirable twisting of the cross section around the path can occur. If this happens, increase the number of CVs in the path to make the change of direction between CVs more gradual. Sharp corners work well, but tight corners do not. For example, try extruding a circle along a linear path with 90 degree angles.

Setting Extrude options

Select Surfaces>Extrude- to open the options window.

Choosing the extrude style

Select a Style option to specify the type of extrusion you want. See "Setting the extrude distance" on page 320 for information on the Distance option.

Flat

If you choose the Flat option, the extrude maintains the orientation of the cross section in space as it moves along the extrusion path.



Tube

Tube is the default extrude style. It sweeps the cross section along the specified path so that the reference vector stays tangent to the path.

Setting the extrude distance

Select the Distance extrude Style to extrude a profile along a straight line. No path curve is required. When selected, the options window changes to include the following:

Extrude Length

Enter a value or drag the slider bar to specify the length of the extrusion. By default, the extrude length is 1.0. The following shows the result when you change the value to 5.0.

Setting the profile normal extrude direction

Direction

If Distance is the selected extrusion Style, the default direction of the extrusion is Profile Normal. This means that the direction of the path is automatically taken from the normal of the profile curve. If the profile curve is not flat (planar), the average normal is used.

Specifying the direction vector

Direction Vector

Click the Specify button to change the default direction for the extrusion.

When you click Specify, you can select X Axis, Y Axis, Z Axis, or Free. If you select an axis button, the extrusion occurs along that axis. For example, if you click the Z Axis button, the extrusion will be linear in the Z direction.

If you select Free, you can enter values in the X, Y, and Z boxes to specify a vector to extrude. For example, the extrusion occurs by 1.0 in the X direction by default. The following example shows what happens if you set X and Y to 0.0 and Z to 1.0 when you extrude a curve.

Selecting the result position

Result Position

If you set Style to Flat or Tube, At Profile is the default Result Position. This means the resulting surface starts at the profile; the path curve is moved to the profile and then the extrusion is performed.

If you select At Path, the profile curve is moved to the path curve and then the extrusion is performed. This results in a surface at the path.

Setting the pivot

Pivot

The Pivot options are only available if you set the Style to Tube.

The Pivot options let you choose the pivot point method to position the profile curve on the extrusion path. If you select At Path as the Result Position, you can choose the profile curve and position it to the pivot point on the extrusion path.

If you choose Closest End Point, the path end point closest to the center of the bounding box of the profile curves is used. This end point is used as the pivot point for all the profile curves. If performing a multiple extrusion, the resulting surfaces are offset from the path. This is the default.

If you select Component, the pivot point of each individual profile curve is used to extrude the profile curve. The extrusion occurs along the components of the profile curve.

See the following examples.

Selecting the extrusion orientation

Orientation

The Orientation options are only available if Style is set to Tube.

If you choose Path Direction, the direction of the extrusion is determined by the direction of the path curve.

By default, the direction of the extrusion is determined by the Profile Normal direction. The direction of the linear path is automatically taken from the normal of the profile curve.

Orientation examples

The following examples show the extrusion using a combination of Orientation modes and Result Positions.

In this first example, Result Position is set to At Profile and Orientation is set to Profile Normal. The path curve is moved and rotated to match the profile curve. This is the default setting.

In this next example, Result Position is set to At Path and Orientation is set to Path Direction.

In this last example, Result Position is set to At Profile and Orientation is set to Profile Normal. The profile curve is moved and rotated to match the path curve.

Selecting the curve range

Curve Range

Set the Curve Range to Complete to extrude the entire profile along the entire path.

Select Partial to extrude only part of the profile along part of the path. This creates a "subCurve" history node (initially set to the whole curve) which can then be edited using the Show Manipulator Tool.

Editing the extruded surface using manipulators

If the Curve Range is set to Partial in the options window, you can use the Show Manipulator Tool to edit the parameter range of part of the curve used in the extrude operation.

In the first example that follows, Tube requires two input curves, so two subCurve history nodes are included in the Channel Box.

Click the heading in the Channel Box to select a subCurve history node, then click the Show Manipulator icon to display the manipulators (if not already selected). Drag the

manipulators to edit the subCurve interactively, or enter values in the Min and Max boxes. In the following example, the profile input curve (subCurve 1) is selected and edited.

Now the path curve (subCurve2) is selected and edited.

If the Distance extrude style is used, click the extrude1 heading to display the manipulator to edit the length of the extruded surface.

Click the subCurve heading to edit the profile curve (the curve used to create the extrude).


Output Geometry


To change the number of polygons created for the surface when creating polyset data, use the Attribute Editor. The polygonal surface must be selected. Click the nurbsTesselate tab to display and edit the Tessellation Attributes and the Mesh Component Display.

Editing the extruded surface in the Attribute Editor

To edit the completed extruded surface, use the Attribute Editor. To open the Attribute Editor, either:


The Attribute Editor includes the options you set in the options window. See "Setting Extrude options" on page 319 for details.

Profile Curve/Path Curve

The Profile Curve and Path Curve boxes let you access the input curves as well as statistical information about these curves. Click the arrows beside the boxes to select the input curves and click the tab to open the Attribute Editors for them.


If you set the Curve Range to Partial in the options window when the extrude was created, you have access to the Attribute Editor for the resulting subCurves. See in for details.



Lofting curves and surfaces Use Surfaces>Loft to construct a surface that passes through a series of profile curves. These curves can be curves-on-surface, surface isoparms, or trimmed edges. Lofting is used most often to create new surfaces from curves or primitive shapes, or to close open surfaces.

Tip

Before you begin, you need at least two profile curves or surface isoparms.

To loft curves:

1 Pick the first curve you want to loft, then Shift-click to pick subsequent curves.

2 Select Surfaces>Loft.

3 The lofted surface is constructed from curve to curve in the order that you selected them. The last curve selected is green by default.

Tip

If you require an even and uniform transition of the surface as it lofts through each profile curve (for example, a boat hull), space the curves evenly.

To add additional curves to a lofted surface:

You can add new curves to an existing lofted surface created with construction history.

1 Select one of the curves you used to create the lofted surface. Notice the lofted surface is displayed in the construction history color.

2 Select the curve you want to add, then select Surfaces>Loft.

The following shows the result when two curves are added to the initial lofted surface.

To loft surface isoparms:

1 While the surface is active, click the Select by component mode icon.

2 With the right mouse button, click the Lines icon and toggle Isoparms on from the pop-up menu.

or While the pointer is positioned over the active surface, use the right mouse button to select Isoparm from the marking menu.

3 Shift-click to select the isoparms you want to loft together, then select Surfaces>Loft.

Setting Loft options

Select Surfaces>Loft- to open the options window.

Changing the loft parameterization

Select one of the Parameterization options to modify the V parameterization of the lofted surface.

Uniform

With Uniform knot spacing, the profile curves run parallel to the V direction. The parameter values of the resulting surface in the U direction are equally spaced. The first profile curve corresponds to the isoparm on the surface at U 0, 0, the second to U 1.0, and so on.

Chord Length

With Chord Length spacing, the parameter values on the resulting surface in the U direction are based on the distance between the start points of the profile curves.

Tips on Knot Spacing

Since lofting is based on the parameter values along the curves, if the curves are all parameterized the same way (each curve is the same degree with an equal number of edit points and identical knot values), the lofted surface will have the same number of spans in the U surface parameter direction. This helps to control the amount of surface data, and the size of the related data file. You can achieve this by copying the original cross sectional

curve, and then transforming and modifying it as necessary. If the parameterization of all the curves do not match, the resulting surface can have considerably more spans than any of the curves used in its construction. If you create the original curves as Edit Point curves with chord length, this results in increased surface complexity.

Changing the loft degree

Surface Degree

You can set the Surface Degree to either Linear or Cubic. This sets the lofted surface to linear or cubic in the U direction.

Reversing the loft direction

Auto Reverse

If Auto Reverse is toggled off, the curves are used as they are which may result in a twisted surface. If toggled on, the curves are automatically reversed. The default in on.

In the following example, the two top curves and the two bottom curves are going in different directions.

If Auto Reverse is toggled off, the result is a twisted lofted surface. If toggled on, the curves are automatically reversed.

If Auto Reverse is toggled off, you can use the Show Manipulator Tool to reverse the curve direction of the original profile curves as needed. Simply click the manipulator handle to reverse the curve direction.

Opening or closing the lofted surface

Close

The Close option determines whether the created surface is closed in the U direction. Close is toggled off by default.


Curve Range

If you set the Curve Range to Complete, the lofted surface passes through the entire curve.

If you select Partial and select the Show Manipulator Tool, curve range manipulators are displayed on the profile curves. This means you can drag the manipulators to interactively alter the portion of the curve to use in the loft. The resulting surface only passes through the selected portions of the profile curves (the subCurves).

Editing part of a lofted surface

To edit part of a lofted surface, set Partial as the Curve Range in the options window. Click the Show Manipulator icon to display the curve range manipulators and editable parameters in the Channel Box. Click the subCurve heading in the Channel Box for the input curve you want to edit.

You can also enter values in the Numerical Input line while a manipulator handle is active.


Output Geometry



Editing the lofted surface in the Attribute Editor

To edit the lofted surface, use the Attribute Editor. To open the Attribute Editor, either:


If you selected curves to construct the lofted surface, the following is displayed:

The options you set in the options window or the Channel Box are displayed. See the option descriptions for details.

Input Curves

The Input Curve sections and available options change depending on which method you used to create the lofted surface. This information is read-only. It gives you access to the history of the lofted surface you constructed. Click the arrow buttons to select the surface, isoparms, or curves and open its section of the editor.

Reverse Curve

If you toggle Auto Reverse off, a Reverse Curve toggle box is displayed for each curve, primitive, or surface isoparm you used to create the lofted surface. Select the Show

Manipulator Tool to also display the reverse manipulators. Click the toggles to reverse the direction of the input curves, or click the manipulators.

In the following illustration, the first curve used to create the lofted surface is selected for reversal.


If you set the Curve Range to Partial in the options window when the loft was created, you have access to the Attribute Editor for the resulting subCurves. See in for details.

Planar Use Surfaces\>Planar to create a trim surface from one or more planar curves.

Important

Make sure that the curve you want to use in a planar trimming operation is a closed curve, a planar curve, or that multiple curves form a closed region. Open the Outliner window to verify that the curve is closed, planar, or that there is a closed area when using multiple curves. For more details, see .

To make a trimmed surface from a single closed curve:

Click on a closed curve or surface isoparm and select Surfaces \> Planar. A trimmed surface is created indicated by the grid that fills the curve. In this example you use the isoparm of a NURBS sphere.

Setting Planar Trim Surface options

Select Surfaces\>Planar- to open the options window.

Selecting the resulting surface degree

Degree

Select either Linear (degree 1) or Cubic (degree 3) for the Degree if the output is a NURBS surface. Cubic is the default.


Curve Range

Set the Curve Range to Complete to create the planar surface along the entire curve.

When you set the Curve Range to Partial you can display manipulators on the planar surface with the Show Manipulator Tool and edit the resulting planar surface along part of the input curve. Click the input curve or isoparms's heading in the Channel Box to display the editable parameters.


Output Geometry


Limitations

Planar surfaces must remain planar. Although the boundary of a planar surface can be manipulated to change the shape of the surface, the surface must remain planar at all times. Although a planar surface can include cut-out areas or holes, the curves that define the holes must be co-planar with the main surface.

Creating trimmed surfaces from open curves

You do not necessarily need a single boundary curve to create a trimmed surface, however, you do need an enclosed region. This can be created by intersecting several curves. You can create trimmed surfaces using curves with overlapping boundaries. Marquee-select the curves and use Edit Surfaces \> Planar to create the trimmed surfaces.

Editing the planar surface in the Channel Box

While the planar surface is active, click it's heading to display the available parameters.

Degree

With the right mouse button, place the pointer in the Degree box and select Cubic or Linear from the pop-up menu. See "Selecting the resulting surface degree" on page 343 for details. The following shows a default cubic degree planar surface, and what happens when you select Linear.

Note

Different degree curves can be mixed together. For example, a polygonal curve (degree 1) can be used to define the cut-out area or hole within the boundary of a cubic curve, as long as both curves are co-planar.

Keep Outside

Type on or off in the Keep Outside box to specify whether you want the trimmed result on the inside or on the outside of the surface. The following shows the default trimmed surface on the inside (off). This means that the planar trimmed curve (the isoparm in this case) remains on the inside of the surface.

When you type on, a planar trimmed surface is created outside of the surface and a hole is trimmed away from the center.



Editing the planar surface in the Attribute Editor

The Attribute Editor for a planar trimmed surface includes the options you set in the Channel Box and options window, as well as a local tolerance slider. Change the slider value to adjust the trimmed surface's tolerance.

Revolving surfaces Use Surfaces>Revolve to construct a surface by revolving a profile curve about an axis. Any curve can be revolved: free curves, surface curves (isoparms), curves-on-surface, and trim boundaries are all valid. The curve can be revolved by either positive or negative amounts, up to a maximum of 360 degrees.

To revolve a curve to build a surface:

1 Draw a curve in the front view so it is perpendicular (Y) in the perspective view. This curve serves as the outline of the surface you want to construct. This is called the profile curve.

2 While the curve is active, select Surfaces \> Revolve to build the surface.

Tip

By default, all selected curves are revolved 360 degrees about the world Y axis. The U parameter direction of the surface is determined by the original curve. The V parameter direction is determined by the direction of the revolve. See for more information. Make sure construction history is on before you create a revolved surface if you want to use the Show Manipulator Tool to edit the resulting surface.

3

When the surface is first created, the revolve history node is active. Click the Show Manipulator icon to see the revolve manipulators. If you want to edit the surface later, you have to select the revolve node in the Channel Box or marking menu (from the Inputs menu) to see the manipulators. You can also edit the parameters for a completed revolved surface in the Attribute Editor.

Using the revolve manipulator

The revolve manipulator consists of handles that let you interactively change the pivot and direction of the revolve axis, and the end sweep angle of the revolve.

Using the axis manipulators

Click the Show Manipulator icon before or after you create the revolved surface to display the revolve manipulator.

Click-drag the handles to change the axis of revolution of the revolved surface interactively, or enter exact X, Y, and Z positions for the active handle in the Numerical Input line. You can also enter precise values in the options window, Channel Box, or in the Attribute Editor.

Tips

If you move the axis endpoints, the axis direction is modified. However, if you move the axis midpoints, the radius of the revolved surface is modified without affecting the axis direction. To snap the axis, start, end, and midpoint to the desired position, use a snap mode. The snap mode icons are located on the Status Line.

See the Basics book for more information about the Show Manipulator Tool.

The following shows what happens to the revolved surface when you transform the axis manipulators.

Using the circle sweep manipulator

To modify the sweep angle, drag the circle sweep manipulator by moving along the arc, allowing the sweep to begin somewhere away from the profile curve. You can also modify the sweep angle by changing its value in the Channel Box.

Note

You cannot use snap modes with the sweep manipulators.

Editing the input profile curve If construction history is on when the revolved surface is created, you can modify the profile curve. This in turn modifies the completed surface. When you select the profile curve, the surface changes color to indicate that it has construction history.

If you have trouble selecting the profile curve, open the Hypergraph or the Outliner and select it from there (Window>Hypergraph or Outliner).

To transform the profile curve, you can either:

use a transformation tool, change its properties in the Channel Box or Attribute Editor, use another operation, such as Extend or Detach Curves.

The following example shows the profile curve extended and scaled.

You can also display the connections for the revolved surface in the Hypergraph window. Select Options>Show>Shape Nodes, click the revolve node (revolve1, for example), then click the Up and Downstream Connections icon.

Setting Revolve options

Select Surfaces>Revolve- to open the options window.

Selecting the X, Y, or Z axis of revolution

Select an Axis Preset option to specify the revolution axis. The default is Y.

Axis Preset

If you set the Axis Preset to X, Y, or Z, you cannot change the values in the Axis boxes. See "Setting a free axis of revolution" on page 356 for more information about the Free option.

In the following example, a profile curve (drawn in the front view) is revolved using each revolution axis in the perspective view.


Setting a free axis of revolution

Free Axis

If you set the Axis Preset to Free, you can enter values in the Axis X, Y, or Z boxes to specify the axes about which the profile curve is revolved. You can also change these values in the Channel Box or the Attribute Editor. In this example, 1 is the value for X, Y, and Z in the Channel Box.

Changing the pivot point location

Pivot

If you set Pivot to Object, the revolve is performed from the default pivot location (0,0, 0). This is the default.

If you select Preset, you can change the X, Y, or Z location of the pivot point by entering values in the Pivot Point boxes. You can also change these values in the Channel Box or Attribute Editor.

The following shows how a revolved surface is created with the default pivot values and what happens when you change the default values to 5 in X, Y, and Z in the Channel Box.

Selecting the surface degree

Surface Degree

The Surface Degree options determine whether the V parameter direction of the surface is created with linear (degree 1) or cubic (degree 3) geometry.

If you select Linear, the surface is constructed with flat facets all around.

If you select Cubic, the smooth polygonal profiles are defined by the original profile curve. This is the default.

You can also change these values in the Channel Box or the Attribute Editor. To select a Degree type from the Channel Box, place the pointer in the Degree box, use the right mouse button and click-drag to select an option from the pop-up menu.

Sweeping the revolved surface

Use the Start Sweep Angle and End Sweep Angle values to specify the angle of revolution in degrees. The default is 360, with a valid range of 0 to 360. You can also change the sweep angle in the Channel Box or the Attribute Editor. See also, "Using the circle sweep manipulator" on page 351 for information on how to sweep the revolved surface with manipulators.

Setting the revolve tolerance value

Use Tolerance

The Use Tolerance options control the accuracy of the resulting revolved surface. You can apply tolerance globally or locally.

If you select None you can change the segments value. See "Defining the number of revolution segments" on page 360 for details.

If you select Local, enter a new value to change the tolerance of the revolved surface. This lets you create the revolved surface so it is closer to the actual surface of revolution.

Global tolerance means the Positional and Tangential value you set in Options>General Preferences>Modeling are used.





Defining the number of revolution segments

Segments

The Segments value determines how many sections are used to create the surface of revolution. With a sweep of 360 degrees, six or eight sections are usually sufficient. The following shows the revolve with the default 8 sections.

You can also change the amount of sections in the Attribute Editor or the Channel Box. The following shows a surface with 20 segments, or sections.

If Use Tolerance is not set to None, the Segments value is automatically computed so that the result differs from the default revolved surface by less than the specified tolerance value.

If Local is set as the Use Tolerance option, the tolerance value of the revolved surface is closer to the actual surface of revolution.

Tip

If animating the sweep angle, change the Segments value instead of the tolerance value to change the numbers of CVs of the surface.


Curve Range

Select Complete as the Curve Range to create the revolved surface along the entire profile curve. This is the default.

Select Partial if you only want to use a segment of the curve for the revolve.

Editing part of the revolved surface

If you set the Curve Range to Partial before you create the revolved surface, a subCurve node is created. Use this node to specify a range of the curve.

To edit this curve range, select the subCurve node and click-drag the curve segment manipulator (click the subCurve heading in the Channel Box, then select the Show Manipulator Tool) or change the Min and Max values.


Output Geometry



Editing the revolved surface in the Attribute Editor

To edit the revolved surface, use the Attribute Editor. To open the Attribute Editor, either:


The options you set in the options window or the Channel Box are displayed. See the option descriptions, "Setting Revolve options" on page 354 for details.

Input Curve

The Input Curve information is read-only. It gives you access to the history of the curve you used to create the revolved surface. Click the arrow buttons to select the curve and open its section of the editor.


If you set the Curve Range to Partial in the options window when the revolve was created, you have access to the Attribute Editor for the resulting subCurves. See in for details.


Creating boundary surfaces Use Surfaces>Boundary to create a three-sided or four-sided surface from three or four curves.

Creating a four-sided boundary surface

Before you begin, you need four boundary curves to define the profile of the surface boundaries.

You can either marquee-select the four curves, or pick the curves in a specific order. After you select the curves you want to use for the boundary surfaces, select Surfaces>Boundary.

Marquee-selecting the curves

If you want to use this method, try to create the curves in the order that you want the boundary surface to be constructed. Keep in mind that the first curve you create defines the U parameter of the resulting surface.

Picking the curves in a specific order

Although a specific order is not necessary when selecting the curves, it is recommended that you pick the curves in opposing pair order. That is, the second curve you select should be the curve that is parallel to the first curve you select. This lets you control which pair of curves will be modified and positioned so their end points match with the end points of the second curve pair. Keep in mind that the first selected curve defines the U parameter direction of the resulting surface.

Creating a three-sided (triangular) boundary surface

Select three curves to define the profile of the surface boundaries, then select Surfaces>Boundary.

Marquee-selecting the curves

If you want to use this method to select the curves, it is important to create the curves in a specific order or the results may not be what you intended. Try to create the two curves that meet at the apex first, then create the third curve. Notice the different results in the following illustration.

Picking the curves in a specific order

Although the direction of the three boundary curves is not important for a triangular boundary surface, the results can differ depending on the order you pick the curves. Remember that the first curve selected defines the U parameter direction of the resulting surface and that the apex always appears where the first curve meets the second curve.

In the following, the curves are selected so that the U direction is determined by a different picking order.

Notes

A 3-sided surface is actually a 4-sided surface with one side that has zero length. If the end points of two side curves are not exactly matched, then a short straight line segment will result instead of a zero length line. The zero length side occurs at the apex of the triangular surface. The term degenerate surface is often used to describe a surface with a zero edge length. Although degenerate surfaces are fine for visual purposes, they may not be compatible with all manufacturing systems.

Setting Boundary options

Select Surfaces>Boundary- to open the options window.

Determining the curve order

The Curve Ordering options affect the resulting surface depending on what is set and how you select the curves.

Automatic/As Selected

Automatic is the default option setting. When As Selected is the curve order setting, the order in which you select the curves determines the resulting surface.

In the following, the first surface is created by marquee-selecting the curves while Automatic is selected. The second surface is created when As Selected is the option setting and you select the curves in a different order.

Setting common end points

Common End Points

The Common End Points options let you decide whether or not the end points should match before the boundary surface is created.

If you select Optional, the surface is created even if the end points don't match (the ends of the curves don't match). This is the default.

If you select Required, the boundary surface is only built if the end points of the curves match exactly. See the following three-sided boundary surface.

To make sure the end points match, remember to select a snap mode from the Status Line when drawing your curves.

To match the end points after you draw the curves:

1 Click to turn a snap mode on in the Status Line, such as Snap to grids.

2 While in component mode, select the edit point or CV you want to move.

3 Select the Move Tool and drag to snap the edit points or CVs to the same position.

Setting the end point tolerance

If you select Required as the Common End Point option, you can change the End Point Tolerance value of the Local end points.

Tolerance

Global tolerance means the Positional value you set in Options>General Preferences>Modeling are used. Positional tolerance is used to determine how close the end points need to be to be considered coincident. The default is Global.

Local tolerance displays the following where you can enter a new value to override the Positional tolerance value you set in Modeling Preferences.

Local tolerance is useful where you want to change these values often, but don't want to change the Global tolerance all the time.

Changing the curve point order and tolerance in the Channel Box

You can toggle the curve Order or End Point selection by typing on or off in the boxes provided in the Channel Box. You can also set the tolerance of the end points by entering a value. These options are also available in the Attribute Editor.


Curve Range

If you select Complete as the Curve Range, the boundary surface is built along the entire profile (or input) curve. This is the default.

Note

If Common End Points is set to Required, set the Curve Range to Complete.

If you select Partial, the boundary surface is built along only part of the profile curves. This also enables you to change the curve range for any of the input curves using the Show Manipulator Tool, thus changing the boundary surface.

Editing part of a boundary surface

If the curve range is set to Partial in the options window, you can use manipulators to edit the construction curves of the boundary surface.

1 Click the Show Manipulator icon and create the boundary surface.

2 Click one of the subCurve headings in the Channel Box to display the manipulators and edit the input curves.

Keep selecting subCurve headings to adjust the input curves as necessary.


Output Geometry



Editing the boundary surface in the Attribute Editor

To edit the completed boundary surface, use the Attribute Editor. To open the Attribute Editor, either:


Input Curves

The Attribute Editor for a boundary surface lists the read-only information for the input curves you used to build the surface. Click an arrow button to select an input curve, then click the tab to open its section of the editor. If Partial is the Curve Range in the options window when you create the surface, information for the subCurves is also available.

The Order and End Point toggles, as well as the End Point Tolerance slider are included in the options window and the Channel Box. See the option descriptions on page 368 for details.

Creating birail surfaces Use the birail tools to create surfaces by combining three or four free-form curves that intersect. Available tools include Birail 1 Tool, Birail 2 Tool, and Birail 3+Tool. The curves


you select can be boundary curves of an existing surface, isoparms, curves-on-surface, or trim boundaries.

If you know which options to set before you create the birail surface, open the options window first, then use the tool to create the surface. Click the option box (

) after the tool name to change the option settings. See the following for details about setting the options for each birail creation method:

"Setting Birail 1 Tool options" on page 378 "Setting Birail 2 Tool options" on page 384 "Setting Birail 3+Tool options" on page 390

Alternately, you can create the birail surface with the default options and then open the Attribute Editor to edit the completed surface. See the following for details about the Attribute Editor for each birail creation method.

"Editing the single birail in the Attribute Editor" on page 382 "Editing the double birail in the Attribute Editor" on page 386 "Editing the multi birail surface in the Attribute Editor" on page 391

Tip

To successfully build a birail surface, the input curves have to intersect the rail curves. If you are building birail surfaces from curves, make sure the profile curves cross the rail curves before you select the birail tools. Open all views to verify the intersection, or try using the front view.

Using the Birail 1 Tool Use the Surfaces>Birail 1 Tool to construct a surface by sweeping one profile curve along two rail curves. You can also construct the surface by reversing the selection order of the rail curves.

To build a birail surface from a single profile curve:

1 Select Surfaces>Birail 1 Tool.

2 Follow the prompts at the Help Line. Click the curve you want to use as the profile curve, then click the two rail curves. The surface is displayed in the construction history color by default.

3 Press Enter to complete the birail surface.







Setting Birail 1 Tool options

Set the tool options before you create the birail surface. To open the options window, select Surfaces>Birail 1 Tool- .

To change the options after the birail is created, use the Channel Box or the Attribute Editor. See "Editing the single birail in the Attribute Editor" on page 382 for details.

Controlling the resulting transformation

Transform Control

As the profile curves are swept along the rails, you can scale them proportionally or non-proportionally while preserving the intersection with the two rail curves. Select either NonProportional or Proportional. NonProportional is the default.

To change the transformation from proportional to non-proportional:

Construct the rail curves in the XZ plane. Construct the profile curve so that the internal CVs are at some constant Y. By scaling non-proportionally, the internal CVs of the birail surface also preserve the constant Y as the profile.


1 In the top view, create the two rail curves. Select Display>NURBS Components>Edit Points to display the edit points on the curves.

2 Click the Snap to points icon on the Status Line, place the first point of the profile curve, and click Snap to points again to turn snapping off.

3 In the front view, continue to place the points to create the profile curve. Select the Snap to points icon to snap the last point to the last rail curve (remember to turn snapping off afterward).

4 Build the birail surface, then while it is active, select a transform mode from the Channel Box. While the pointer is in the Transform Mode box, click with the right mouse button to select a Transform Mode from the pop-up menu.

The following example shows what happens to the birail surface when you switch between the transform modes.

Blending the profile curves

Edge Blending

You can use the Edge Blending option, First Edge, only if the profile curve is a surface curve. If First Edge toggled on, the constructed surface is tangent continuous to the surface underlying the profile.

Rebuilding profile or rail curves

Toggle one of the Rebuild Options on to rebuild a profile curve or rail curve before it is used to create the surface.

Profile Curves

Since only one profile curve is necessary when building a single birail surface, First Edge is the only available Profile Curves rebuild option.

Rail Curves

For Rail Curves, the First Edge option refers to the first input rail curve you select when you build the surface. The Second Edge option refers to the second, or last, curve you select.

To display rebuild options and edit the profile and rail curves:

If you toggle one of the Rebuild Options on, rebuild nodes are inserted between the profile curve or rail curves and the birail surface creation node. This means the profile curve or rail curves can be selected from the Channel Box and rebuilt using the parameters and options provided in the Channel Box or in the Attribute Editor.

The following shows the Channel Box and Attribute Editor for a profile curve when rebuild is toggled on.

To access the Attribute Editor for the selected curve:

Click the option box ( ) beside Rebuild Curve from the History list menu on the Status Line.

Click the option box ( ) beside Rebuild Curve from the Input pop-up menu in the marking menu.

See for details about the options provided in this Attribute Editor.


Output Geometry


Editing the single birail in the Attribute Editor

To edit the completed single profile birail surface, use the Attribute Editor. To open the Attribute Editor, either:


Transform Mode

The Transform Mode options are included in the options window and the Channel Box.

Input Profile /Input Rails

The Input Profile, and Input Rail 1 and Rail 2 information is read-only. It gives you access to the input curves you used to build the birail surface. Click the arrow buttons to select the curves if you want to edit them.

Tangent Continuity Profile

The Tangent Continuity Profile toggle lets you turn tangent continuity on or off for the input profile curve. You can use this to make the resulting surface tangent continuous to the surface underlying the profile curve. You can also toggle this option on or off in the Channel Box in the Tangent Continuity Profile box.

Note

For this toggle to take effect, the profile curve must be a curve-on-surface.

Using the Birail 2 Tool You use the Surfaces>Birail 2 Tool to create a surface by blending two profile curves along two rail curves.

To build a birail surface from two profile curves:

1 Select Surfaces>Birail 2 Tool.

2 Follow the prompts at the Help Line. Click the curves you want to use as the profile curves, then click the curves you want to use as the rail curves. The surface is displayed in the construction history color by default.

3 Press Enter to construct the double profile birail surface.

Setting Birail 2 Tool options

You can set the tool options before you create the birail surface. To open the options window, select Surfaces>Birail 2 Tool- .

To change the options after the birail is created, use the Channel Box or the Attribute Editor. See "Editing the double birail in the Attribute Editor" on page 386 for details.

Most of these options are included in the Birail 1 Tool options window. See "Setting Birail 1 Tool options" on page 378 for details.

Since you need two profile curves to create a double profile birail surface, an extra Edge Blending toggle (Second Edge) and profile curve Rebuild Option toggle (Last Edge) is included in this options window.

Surface Blend is the only option that is not included in the Birail 1 Tool options window.

Defining the surface blend




Surface Blend

The Surface Blend factor value lets you alter the degree of influence the profile curves have on the intermediate profiles of the created surface. For example, a value of 1.0 means the first selected profile curve has a greater influence than the second profile curve. By default, both selected profiles have an equal influence value of 0.5.

You can also change the Surface Blend value in the Channel Box. While the birail surface is active, click the heading to display the parameters and enter a new value in the Blend Factor box.

Editing the double birail in the Attribute Editor

To edit the completed double profile birail surface, use the Attribute Editor. To open the Attribute Editor, either:


The Transform Mode and Blend Factor options are included in the options window and the Channel Box. See "Controlling the resulting transformation" on page 378 for details about Transform Mode, and "Defining the surface blend" on page 386 about Blend Factor.

Input Profile / Input Rail

Because you use four curves to create a double-profile birail surface, the Input Profile and Input Rail information boxes list all of the curves you used as profile and rail curves. This gives you access to the input curves you used to build the birail surface. Click the arrow buttons to select the curves if you want to edit them.


The Tangent Continuity Profile toggles let you turn continuity on or off for the input profile curves. Using this toggle, you can build a tangent continuous surface with the surfaces underlying the profile curves. You can also toggle this option in the Channel Box by typing on or off in the Tangent Continuity Profile boxes.



The Tangent Continuity Profile toggles are only valid provided the profile curve is a surface curve (isoparm, trimmed edge, curve-on-surface).

Using the Birail 3+ Tool You use the Surfaces>Birail 3+ Tool to create a surface by blending multiple profile curves along two rail curves.

To build a birail surface from multiple profile curves:

1 Select Surfaces>Birail 3+ Tool

2 Follow the prompts at the Help Line. Select three or more profile curves, then press Enter to confirm your choice.

3 Select the two rail curves. The surface is displayed in the construction history color by default.

4 Press Enter to construct the birail surface.

Setting Birail 3+Tool options

You can set the tool options before you create the birail surface. To open the options window, select Surfaces>Birail 3+ Tool- .

To change the options after the birail is created, use the Channel Box or the Attribute Editor. See "Editing the multi birail surface in the Attribute Editor" on page 391 for details.

Most of these options are included in the Birail 1 Tool options window. See "Setting Birail 1 Tool options" on page 378 for details.

Since you need two profile curves to create a multi profile birail surface, an extra Edge Blending toggle (Second Edge) and profile curve Rebuild Option toggle (Last Edge) is included in this options window.

Editing the multi birail surface in the Attribute Editor




To edit the completed multi profile birail surface, use the Attribute Editor. To open the Attribute Editor, either:


Input Profile / Input Rail

Because you use multiple curves to create a multi-profile birail surface, the Input Profile and Input Rail information boxes list all of the curves you used as profile and rail curves. This gives you access to these input curves you used to build the birail surface. Click the arrow buttons to select the curves if you want to edit them.


The Tangent Continuity Profile toggles let you turn continuity on or off across the first to last profile curve.

Note

For this toggle to take effect, the profile curves must be curves-on-surface.

You can also toggle this option in the Channel Box by typing on or off in the Tangent Continuity Profile boxes.

You can also select a different Transform Mode (Proportional or Non proportional) in the Channel Box.

While the birail surface is active, select a transform mode from the Channel Box. While the pointer is in the Transform Mode box, click with the right mouse button to select a Transform Mode from the pop-up menu.

See "Controlling the resulting transformation" on page 378 for details.


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