Template:Maya2017 Geometry Types
Different types of Geometry
Maya uses three different types of geometry. Every type has it’s own purpose. The three types are: Polygons, NURBS and Subdivision surfaces, often called subdivs. Each of them requires a different method of editing. Therefore a basic understanding of each geometry type is necessary when you start modeling.
Polygons
A polygon is a surface that consists of three points called vertices. The three vertices together form a triangular surface called a face. The edges of this face are straight lines connecting the vertices, so a face is always a flat surface. A polygonal object is constructed out of these faces. In Maya a face can consist of more than three vertices. This is for easy editing purposes, but in fact the faces are always subdivided in triangular faces.
Modeling with polygons is a fast and easy way of modeling. Editing a polygonal object is basically moving vertices of faces the object is build off. Therefore polygon geometry is suitable for most common modeling tasks. The downside of polygons rises in the fact that faces are always flat. In cases of curved surfaces, polygon geometry is always an approximation of the curved surface. By adding more subdivisions, i.e. more and smaller faces, it is possible to create a better approximation. This however results in more data and a 'heavier' model.
NURBS
NURBS is an abbreviation of non-uniform rational B-spline. NURBS geometry is created by two or more curves defining the surface in between. The way those curves are generated, makes NURBS geometry very flexible. A curve consists of a start point, an end point and several control vertices in between, defining the tangent of the curve. Depending on the 'degree' of the curve, defining the amount of control points, a curve can be linear, with straight angles, or curved. NURBS surfaces consist of the aforementioned control vertices (CVs), defining the tangent of the surface, and curves lying on the surface, called isoparms. Those isoparms are the curves the surface is build from.
NURBS geometry allows you to create surfaces curved in multiple directions. This geometry type is very useful for more complex and curved objects. The amount of flexibility is very high. Calculating NURBS curves and surfaces however, is a lot more demanding than polygon geometry. The choice of geometry type for a certain modeling task depends on the demand of flexibility, modeling speed and precision.
Subdivision surfaces
Subdiv geometry is a sort of a combination of NURBS and polygon geometry. In search of a geometry type with the flexibility of NURBS and the easy editing of polygons, subdivs were developed. Subdiv geometry will not be discussed in our courses, so for more information on subdivs we direct you to Subdivision Surface on Wikipedia or other sources.
