Introduction - Computer Animation: Algorithms and Techniques - page 16

Many aspects of the rendering can be selectively turned on or off to provide great flexibility in
giving the animator clues to the finished product's quality without committing to the full computations
required in the final presentation. Often, the resulting animation can be computed in real time for
very effective motion testing before committing to a full anti-aliased, transparent, texture-mapped
rendering. Wire frame rendering of objects can sometimes provide sufficient visual cues to be
used in testing. Shadows, smooth shading, texture maps, environmental maps, specular reflection,
and solid texturing are options the animator can use for a given run of the rendering program.
Even in finished pieces of commercial animation it is common practice to take computational short-
cuts when they do not affect the quality of the final product. For example, the animator can select which
objects can shadow which other objects in the scene. In addition to being a compositional issue, selec-
tive shadowing saves time over a more robust approach in which every object can shadow every other
object. In animation, environmental mapping is commonly used instead of ray tracing; photorealistic
rendering is typically avoided.
Computer animation is well suited for producing the equivalent of test shots and pencil tests. In fact,
because the quality of the separate stages of computer animation can be independently controlled, it can
be argued that it is even better suited for these evaluation techniques than conventional animation.
1.4.1 Computer animation production tasks
While motion control is the primary subject of this topic, it is worth noting that motion control is
only one aspect of the effort required to produce computer animation. The other tasks (and the other
talents) that are integral to the final product should not be overlooked. As previously mentioned,
producing quality animation is a trial-and-error iterative process wherein performing one task may
require rethinking one or more previously completed tasks. Even so, these tasks can be laid out in
an approximate chronological order according to the way they are typically encountered. The order
presented here summarizes an article that describes the system used to produce Pixar's Toy Story
[ 16 ]. See Figure 1.7 .
￿ The Story Department translates the verbal into the visual. The screenplay enters the Story
Department, the storyboard is developed, and the story reel leaves. These visuals then go to the
Art Department.
￿ The Art Department , working from the storyboard, creates the designs and color studies for the film,
including detailed model descriptions and lighting scenarios. The Art Department develops a
consistent look to be used in the imagery. This look guides the Modeling, Layout, and Shading
Departments.
￿ The Modeling Department creates the characters and the world in which they live. Every brick and
stick to appear in the film must be handcrafted. Often, figures with jointed appendages, or other
models with characteristic motion, are created as parameterized models. Parameters that control
standard movements of the figure are defined. This facilitates the ability of animators to stay on the
model , ensuring that the animation remains consistent with the concept of the model. The models
are given to Layout and Shading.
￿ On one path between the Modeling Department and Lighting Department lies the Shading
Department . Shading must translate the attributes of the object that relate to its visual appearance
into texture maps, displacement shaders, and lighting models. Relevant attributes include the