More modeling techniques

The basic concept of subdivision surfaces is not new as it is originally published in a paper written by current Pixar's CEO Ed Catmull in 1974. However the technology did not get popular until it was used by Pixar in modeling Geri's head in a movie. They had realistically designed the creases both hard and soft in Geri's head, noses and knuckles and clothes.

New technologies arise from university labs. One such example is the photogrammatery software that creates 3D geometry from analyzing multiple 2D Photographs by interpolating corresponding points between these photos.

It is all about the design data and its applications. If it is only to visualize (say in video games or movies) and not for manufacturing, there is no need for a lot of geometry. With little geometry and detailed textures and sophisticated bump and displacement maps shaders can represent a wide variety of models.

Unlike geometry based on some primitive shapes or NURBS or just plain old polygonal meshes, mathematically described implicit surfaces also known as isosurfaces are the basis for functional modeling. Surface is defined using the superposition of Gaussian potentials representing individual atoms. Many design software like 3DS Max and Maya have a feature called metaballs thas implements this technique.

Constructive Solid Geometry is the technique widely used by MCAD software and B-Rep (boundary representation) is used by CATIA, Autodesk Inventor, etc. In CSG, complex objects are represented as boolean operations on simple primitive solids like cone, sphere, tori and blocks. Some CAD/CAM applications use this technique.

In B-REP, objects are defined using topology and geometry. Topology represents the connectivity between various entities like SHELLS, FACES and EDGES. Geometry actually defines the data underneath the FACE or EDGE.

I will talk about animation in computer graphics tomorrow.