CG Modeling 3: Advanced - An Introduction to Computer Graphics for Artists - page 278

Fig. 15.5 Procedural railway tracks (Courtesy of Freek Hoekstra)

govern behavior of 3D elements like particle systems or models, but they do not
generate the models themselves.
Using a procedural application to generate geometry requires a good analysis of
the kind of object you intend to build. This is because the rules you create to con-
struct the model must include all that is needed to generate the object, because you
will not want to edit it yourself. The reason you don't want to adjust a procedural
model is that you wouldn't use the tool unless the thing you are making is so com-
plex that you don't have the time to make it by hand (Fig. 15.6 ).
One of the fi rst uses of procedural tools to generate full models was to make
plants. Plants are pervasive in our environment, but they are extremely complex as
objects (Fig. 15.7 ). Imagine trying to model individual blades of grass, or pine
needles on trees and then you will understand the scope of the problem (Fig. 15.8 ).
If you want to fi ll a forest with a variety of lush undergrowth as in the fi lm Brave
(2012), you cannot do it by hand. With procedural tools, the shapes of the individual
parts of the plants can be defi ned, the way they grow, and the way they behave in
an environment to aid in appropriate placement of the millions of individual plant
parts that are generated.
In games, procedural tools have been used more sparingly. The reason for this is
partly that poly budgets were so low that it would be diffi cult to make good use of
tools whose chief advantage is when working with extremely large numbers of
polygons, but also because procedural tools do not behave like traditional CG
modeling tools. Artists needed to make an extra effort to learn how to use them, but
once they did, they would fi nd that they were capable of doing much more in less
time. For example, at Electronic Arts, the world's largest video game developer,
they found that they could reduce the time it took to generate football stadiums from
months to days.