Modeling

Topology

Topology describes an object’s shape, number of spans, and degree. For polygon objects this includes vertex positions.

Non-manifold topologyNon-manifold topology cannot be unfolded into a continuous flat piece. Some modeling and rigging operations in Maya will not work with non-manifold geometry. Modeling operations that can create non-manifold geometry include, extrude edge, reverse normals, merge vertices, delete face, and collapse face or edge.

Example of Non-Manifold Topology

•More than 2 faces share an edge

•Two faces share a single vertex without sharing and edge

•Adjacent Faces have opposite normals

Curves

Curves are defined by multiple points and deviate from a straight path without any sharp breaks in angularity.

Splines

A Spline is a curved line shaped by weights. By adjusting the number and position of weights, a spline produces a smooth curve that passes through a desired set of points.

Controlled CurvesSplines are considered controlled curves because they are created from a defining polygon made up of control points. This defining polygon is invisible, but contains weight information that can be used to adjust the shape and angle of the curve.

Splines

•Linear Spline – A spline made up of straight line segments connecting control points. Only 2 control points are needed to generate a linear spline.

•Cardinal Spline – A spline curve that always passes through all of its control points. A Tension value adjusts the tangents at each control point.

•B-Spline – A spline curve that is defined and bounded by its control points, but it does not pass through them.

•Bezier Curve - A spline curve that always passes through all of its control points. A Bezier curve is controlled by lines tangent to the control points. Manipulating the tangents allows the user to control the direction and tension of the curve segment.

•NURBS – A spline curve that does not pass through its control points. NURBS offer a high degree of curve control eat each control point. By default control vertices on a spline have an equal weight, this is referred to as a nonrational curve. The weight of control vertices on a NURBS curve can be modified and adjusted, this is referred to as a rational curve.

Non Planar Polygons

A polygon is planar if all of its points lie in the same plane. A triangle is always planer because its 3 vertices define a plane. A polygon is non planar if it has more that 3 vertices and any of the other vertices are not in the same plane.

Invalid Geometry

Invalid Geometry occurs when there are vertices that are not on an edge, or when there are edges that are not part of a face. In Maya the polygon cleanup function will correct invalid geometry

TessellationTessellation can be described as a converting a 3D surface into an polygon approximation of the original surface. When a NURBS surface is converted into a polygon surface, the surface is tessellated into a polygon object. Most renderers convert all surfaces to polygons at render time.

Nickeling

Nickeling describes the situation when faceting is visible on low resolution polygon geometry. Nickeling often occurs a a result of low tessellation setting when converting a NURBS surface to a polygon object.

Procedural Modeling

Mathematical functions are sometimes used to model natural like terrain, mountains and rock formations. Procedural modeling is useful for creating large areas of terrain that look natural and non-repeating.

3D Sculpting

The process of pushing a pulling control points is referred to as 3D sculpting. This can be accomplished by selecting individual control points and moving them into a desired position. In Maya the Sculpt Polygons Tool allows the user to push a pull sections of polygon vertices with a virtual brush.

Mirroring

The process of duplicating surface across an axis to create a symmetrical copy of the original object is called mirroring. Mirroring is a common method used to model symmetrical objects like human figures, animals, and cars.

Example Images

Example Images