4.1 - 3D Modeling¶

3D modeling is the process of developing a mathematical representation of an object. The result is a 3D model which can be used for rendering 3D scenes or to prototype newly designed widgets. Creating 3D models is an art that requires extensive training. In the movie and game industries people often become experts at 3D modeling and that is their sole job. The next time you watch a movie that contains special effects using CGI, notice the number of modelers that are listed in the credits at the end of the film.

Note these characteristics of 3D models:

• The goal is to represent the form of an object, so an object’s surface is often the only thing that is modeled. There are exceptions, such as a model for simulating the inner workings of an engine.
• A 3D model is a typically a polygonal mesh, which is a set of connected polygons. Polygons with more than 3 edges are converted to triangles for rendering. These are called triangular meshes.
• The number of polygons used to represent the form of an object determines the accuracy of the model. More polygons means greater accuracy, but at the expense of more memory requirements and slower rendering.
• The total number of triangles in a scene is often the deciding factor in whether the scene can be rendered in under 1/30^th of a second. It is common to reduce the number of triangles in one model so that another model can have more.
• A model is manipulated as a unit. If parts of an object move independently, then those parts must be modeled separately. For example, if you have a box whose lid opens, this would be modeled as two separate objects - a five sided box and a lid.