Graphics Programs Reference
In-Depth Information
Polygons are a welder's tool. Polygon modeling involves tearing and extruding from
larger pieces and welding several surfaces together to form a desired whole. Orthogonal
models (models with straight lines and sharp corners) are created more easily with polys.
A clay sculptor might prefer NURBS. Pushing and pulling CVs to create subtle curves
on the surface is like working soft clay with your fingertips; you're nurturing something
into shape with the fine art of pressure.
Subdivision surfaces combine the best of both worlds. An artist can begin with a
rough shape, chisel it out coarsely, and then switch to finely detailed sculpting by adding
levels of detail to the sculpture only when and where needed. Subdivision surface model-
ing excels at creating organic shapes out of single surfaces.
In the end, converting everything back to polygons is almost always preferable. Why?
The available rendering applications all turn everything to polygons (a process called
tessellation
) when they render the scene. You can save yourself some memory and time
and be the master of your own models by trying to go back to polygons as often as is
reasonable.
Using Primitives
Primitives
are the simplest objects that you can generate in Maya (or in any 3D appli-
cation). Primitives are simple geometric shapes—polygons, subdivisions, or NURBS.
Typically, they're used to sculpt models, as you saw with the Solar System project in
Chapter 2, “Jumping in Headfirst, with Both Feet.”
Because you can define the level of detail of the primitive's surface, primitives offer
great sculpting versatility through vertex or CV manipulation. You can create polygonal
primitives using practically any level of subdivisions to define the number of vertices and
faces. NURBS primitives can be created with almost any number of
sections
and
spans
to
define the number of isoparms and CVs.
Spans
are isoparms that run horizontally in a NURBS surface;
sections
are isoparms that run
vertically in the object.
Starting with primitives, a modeler can create highly complex and detailed models.
You may find it helpful to analyze your modeling subjects into forms and shapes that
fit in with Maya primitives to get a better sense of how to begin a modeling assignment.
Figure 4.6 shows all of Maya's primitives, NURBS, polygons, subdivisions, and volume
primitives. Quite different from geometry primitives, volume primitives are used for
lighting and atmosphere effects such as fog or haze and don't play a part in modeling.
