Building a Teapot

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Lesson 3 Building a Teapot This tutorial will focus on building surfaces while using construction curves. You will also use the surface intersection tool and understand the great advantage of a Construction Tree based modeling environment. • NURBS curves. • Lathe. • FillPath. • EdgeExtract. • Pipe. • Birail. • Surface Intersections. • Blending.

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This lesson can be completed in about half an hour. You will start modeling the base of the teapot by defining the curve that will then be revolved.

Organizing your workspace 1) If you are already working with solidThinking, choose the

New command from the File main menu and save the scene you were working on. Otherwise, you must first run solidThinking.

2) Choose the default layout option from the Layouts panel

(choose View4Layouts).

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3) Open the Grid Setup panel by selecting Edit4Grid Setup. 4) Choose the Grid#1 tab and set X, Y, and Z to 0.5.

5) Then, choose the Grid#2 tab and set X, Y, and Z to 1.

6) Leave all grids visible and enable Snap to Grid 1 as in the next picture.

Then, click the Close (X) button. Note: solidThinking allows you to define up to four different grids, each of them with its own origin and spacing, grid type, and color.

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Drawing NURBS curves

You will now draw the curves that will later be used for the construction of the teapot body.

1) Click the NURBS curve modeling tool icon or select the

Tools4Curves4Nurbs curve menu item. This tool enables you to draw a NURBS curve.

2) Draw the curve you see in the picture of the next page

following the same points.

Remember that the first click determines the object working position’s axis (or the created curve’s axis) which in this case will remain at coordinates 0, 0, 0; thus, upon the first data request, press Enter to confirm the original coordinates, and, after this step, you will be able to begin positioning the points on the grid. Press Spacebar to end points insertion.

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3) To enlarge the Front view, click the Zoom icon in the titlebar and drag in the view without releasing the mouse button.

4) Now, you can create a second curve that will be used to construct the teapot lid. This is another simple curve you create using the NURBS modeling tool. The working axis is the same.

Draw the curve as in the picture below starting from the top,

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then press Alt + e , which is the shortcut for the New Entity command. Note that while the console is prompting you an operation, the Modeling Tool panel is disabled but you can still use the command shortcuts. If you do not want to use the shortcut, you can press Spacebar and then, in the Modeling Tool panel, press the New Entity button.

Click in the view and place a new point as in the picture below, then press Spacebar .

To obtain the corner you could also position two points at the same place but this approach is less correct from a mathematical point of view. In any case, the number of replicated points should NEVER be higher than "curve order - 1", i.e. if you have a curve of order 3, you can replicate only 2 points at the same place.

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Creating a revolved surface

To obtain the body of the teapot you can use the Lathe modeling tool, which creates revolved surfaces by rotating around any user-defined axis. 1) Click the Lathe icon or choose the Tools4Surfaces4

Lathe command. 2) Click the first curve and press Enter to confirm the values

in the console: 360 degrees of rotation; revolution axis 0, 0, 0; vertical axis.

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3) By now, you have created the base and, by repeating the

procedure for the other curve, you will attain the basic teapot as the one in the following picture.

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Building the teapot spout

The spout of the teapot can be easily created by using the Birail Modeling Tool. 1) Start with a circular section that you can get with the Circle:

center, radius modeling tool. 2) Draw a circle with center 0, 0, 0 and radius 1.

3) Design two curves - using the NURBS modeling tool - like

the ones you can see in the pictures below which show the curves in relation to the teapot body. They will represent the two curves to be traced with the birail function in order to build the spout.

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Note: The birail surface is created according to the rails; thus, you can position the circular section at your convenience, depending on your needs.

4) Now, apply the Birail function by clicking it. Select first the

circle (the section of the shape to be created) and then the two curves you have just attained. The outcome will be as the one shown by the following illustration.

Now, due to the possibility to find the intersections between two surfaces, you will discover how to split the spout and retain only the part external to the body of the teapot. You will turn body and spout of the teapot into a single object.

5) Select the Surface Intersection modeling tools. 6) At the program console prompts, select the two intersecting

surfaces.

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7) Once you have selected both surfaces, the console prompts Store each face as a separate object? Type N so that the splitting of the intersecting surfaces outputs a single object composed by all the resulting faces.

8) Since the Intersect modeling tool offers the additional

possibility to choose whether to split either the two intersecting objects or only one of the two, the program console prompts Choose which curves will be split and offers you three options: Both, 1st, 2nd.

9) If you type B (Both), you will split both surface #1 and

surface #2. By choosing 1st or 2nd you will only split the surface #1 or the surface #2 respectively. Type B.

10) You can now choose a single face (in our case the internal

part of the spout) by picking it while holding the Alt key down. You can then use the Edit4Delete command to delete the picked face.

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Using pipe to create the handle

You now need to design the handle, which is formed by three parts: the first is the section of a round tube that is adapted to the natural curve of the object; out of this tube comes the second piece which is a slender black metallic bar; and, on the upper side, an anatomical hand-grip equates to the third part. We will start using Pipe, a modeling tool that lets you create a surface by sweeping a cross sectional profile curve along a second path called extrusion path. 1) First, draw a NURBS curve as in the pictures below. It will

be our extrusion path.

2) Then, create another circle with a radius of 1. It will be used as cross sectional profile. Working in the Top view you can easily place its center in correspondence of the last point of the extrusion path. Anyhow, the circle can be positioned wherever you like as the extruded surface is created with reference to the extrusion path and not to the profile.

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3) Choose the Pipe function. At the console prompts, select first the circle and then the curve you have just drawn, thus building the first portion of the handle.

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4) To specify position of the extruded surface according to the sectional curve, you must switch on the Origin option in the Align to section of the Modeling Tool panel.

5) As you did for the spout, use the Surface Intersection

modeling tool to split the surface. At the program console prompts, select the two intersecting surfaces and type N so that splitting of the intersecting surfaces outputs a single object composed by all the resulting faces. At the prompt Choose which curves will be split, type B.

6) Pick the part of the handle internal to the teapot base while holding the Alt key down. You can then use the Edit4Delete command to delete it.

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7) You now need to plug up the frame; therefore, you have to create a cap to place at the end of the tube. This is not difficult to do.

First, choose the Edge Extract modeling tool and select the handle surface, then pick the edge you want to extract and press spacebar to end edges selection.

8) Once you have extracted the circle form the surface, you can

fill it: choose the FillPath modeling tool, then select the circle. Press Spacebar .

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9) Create the second bar that serves to hold the handle by first drawing a NURBS curve.

Then, create a circle of radius 0.2 in the Right view placing its center in correspondence of the last point of the extrusion path.

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Finally, via Pipe function, create the entire metallic bar.

10) All you are left with is the grip, and you will obtain it by

using a simple Birail function. Draw an ellipse in the Right view and adjust its position in the Front.

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Then, two curves as in the pictures below to delineate the shape of the grip itself. Draw both the two curves starting from the left.

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11) Now select the Birail modeling tool and then, in the same order, the circle you have just created, the lower curve (the wavy one), and the upper curve. The result is illustrated in the following pictures: the handle is created with respect to the rails but you can modify its position by simple adjusting the values of Point on Rail#1 and Point on Rail t#2 in the picture respectively, 0.25 and 0.75.

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12) Select EdgeExtract and the grip surface: when this is green, pick the external curve that is now blue. Upon selection, it turns yellow meaning that the curve is extracted.

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13) Ultimately, use FillPath to close the open portion of the grip.

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If you don’t like, for example, the lid surface you can take advantage of the Construction Tree to modify the construction profile. Just select the curve while you are in Object mode, then switch to Edit mode and edit control points.

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While you modify the construction curve, the surface is interactively updated.

You have just completed your project! Its form has been fully realized and, as you can tell by looking at the picture below, it already grants an optimal representation.

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