Validation of CG Models - An Introduction to Computer Graphics for Artists - page 113

Chapter 9
Validation of CG Models

9.1 Introduction

A cobweb may be defi ned with the same clarity and strength as a newly built
suspension bridge and it should be if it is to be rendered correctly. In the same way,
a simple white cardboard box can be constructed so sloppily that it is impossible to
import into a game engine, or render for a single frame of animation. No matter
what you make, it must be clean. The term clean geometry refers exclusively to the
contents of a 3D fi le when those contents are free of errors and well organized. The
goal of this chapter is to explain what clean geometry is.
There are many things that can go wrong during the modeling process to corrupt
your geometry. These are technical errors . Sometimes, you will be forced to
take intermediate steps during construction of an object, like subdividing a wall
into a grid to fi nd the correct spacing of a group of windows. If you forget to
take down the construction edges after you've built the windows, you've made
a construction error .
If you do not take the time to fi gure out what every single item in your scene is,
and how you intend to fi nd it again once it is built, you will have organizational
errors . An example of this is naming. If everything in your scene is given a default
name, you will have hundreds or thousands of objects with indecipherable names.
The three types of error described here, technical , construction , and organizational
prevent geometry from being clean. Likeness errors interfere with the likeness of
your object. An object with serious likeness errors cannot be used even if it is tech-
nically perfect.
This chapter provides examples of each of these error types. If your fi le contains
any of the listed errors, you do not have clean geometry and must fi x your
object. This is because, when it comes to errors, the professional standard is to
have none.