Edges, Patches and Vertices in CG Animation

Author: Daniel Kreimer

Author: Daniel Kreimer

A huge benefit of patch models is their capability to represent smooth surfaces easily. Unlike polygonal models, patch models require less detail to represent smoother, more contoured shapes. Patches are made up of components similarly named as a Polygonal model's. First, a Patch model is actually made up of several smaller patches. Patch's surfaces, in 3D programs, are defined as four-sided surfaces. Each side is referred to as an edge. Each corner of a patch has a point called a vertex. Lastly, there is a Lattice that defines the overall shape of the patch itself. . Although the naming scheme is similar to polygonal models, that is where the similarity ends. The vertices of a patch have Bezier tangent handles, very similar to the Bezier splines that you can create within your 3D program. Bezier splines are curves defined by control points, using parametric polynomial mathematics, which only affect the local region of the curve and not regions beyond control points on either side. Bezier was a French mathematician. The tangent handles of patch vertices control the overall curvature of the patch around the area of the vertex. By manipulating the vertex's handles, you can alter the shape of the patch from that corner. An important note about Bezier handle control: the handle alters only the shape of the patch it is associated with. It does not alter the shape of neighboring patches. This is a crucial difference between patches and NURBS objects, discussed later in this chapter. You use edges of patches to alter the shape of a patch along a specific edge or to define where you want to add patches onto the existing patch. This is primarily how patches work-by propagation. By adding adjoining patches to existing patches, you can build complex surfaces easily. Patches themselves can be defined by either a Quadrilateral surface or by a triangular patch. Triangular patches work best for corners or places where a Patch surface may need to come to a peak. For general purpose use, however, a quadrilateral patch, or QuadPatch, works best. About the Author:

Daniel has been writing articles for nearly 4 years. Come visit his latest website over at http://portableairconditioningunitsdeals.info/ which helps people find the best Portable Air Conditioning and information they are looking for Portable Ac Units.

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