Spring 1999 CS302 Assignment #6
by Dan Garcia
Design the first course exam. Try to include problems from each of Bloom's
categories (recall; comprehension, translation interpretation; application;
analysis; synthesis; and evaluation). Also list the goals for each problem,
and provide intended solutions.
Question 1 (6 points)
The first question is a warm-up recall question, intended for them
to relax a bit (it's made relatively easy). It tests whether they remember
the buzzwords ray-tracing, expensive, and what ray-tracing is.
Your animation partner Buzz says you should try ray-tracing your
entire movie. Your other partner Woody disagrees because he says it would
be too expensive. What does Woody mean?
Woody means that it would be too computationally expensive,
i.e. that it would take too much time given the computational resources
at your disposal.
Question 2 (10 points)
This question is also a recall question, but here it's intended
to see if they were paying attention to the films we showed early on.
We saw many seminal computer animation shorts in the first few
weeks. Briefly, list one of the films and describe why it was ground-breaking.
There are several valid answers. Here are a few:
by Marceli Wein was the
first animation to use a technology which allowed morphing of the representative
splines defining the lines of the images.
- Le Paysagiste: Mindscape by Jacques Drouin was one of the
first animations to use a technology called pinscreening wherein the depth
of a pins controls the local brightness. The pinscreens are like the coffee-table
toys you often play with that save the 3-d state of your face or hand when
you put it in.
- Luxo, Jr by Pixar was
the first animation to be nominated for an academy award, as well as the
first to have several technical achievements, such as self-shadowing.
Question 3 (20 points)
This question tests whether they understand the rationale for performing
animation subtasks in a particular order. Specifically, it's remembering
that the sounds are always done first so that the timing of the animation
can be synchronized. It's also because animation is fully under our control
so it's easy to shift things around, whereas audio is less under our control.
Your friend Z suggests re-ordering the computer animation design
process. He wants to add the sound last, after the animation is finished.
Briefly, what are two disadvantages of this method?
There are several disadvantages to adding sound last:
- The animators won't have a good idea of the timing - the frame time
sheets they use are based on the soundtrack. They'd have to animate "on
- You can forget about lip-syncing. There's no way to animate that without
the actual sounds.
- Some sounds are small, and these can be moved around in the composition
process (the process that merges the audio and video) to synchronize with
the motion. Others can't (e.g. a pre-recorded speech or soundtrack) and
thus there has to be a very tedious iteration process to get the motion
and sound to line up.
Question 4 (24 points)
This question tests whether they the recognize the relationship
between computer and tradiational animation. Here they're asked the bigger
picture why we go through such effort to teach them these tools rather
than just hand-draw things. They also need to understand why folks still
do draw things.
List three that are easy to do in computer animation but difficult
in traditional animation, and three things easy to do in traditional animation
but hard in computer animation.
|Easy w/computer, hard w/traditional
||Easy w/traditional, hard w/computer |
- Changing viewpoints, moving the virtual camera around.
- Changing the textures / colors / lights of the scene.
- Making any changes at all through several iterations. Very little of
traditional animation can be re-used between iterations.
- Getting characters to look 3-D.
- Real physics to the motion.
- There are tools to facilitate so many tasks, like libraries of motions,
textures, etc. Most everything with traditional animation has to be created
from scratch every time.
- You can import scientific data (say of a cloud formation) and use it
in your animation.
- There are lots of techniques to get realistic motion - data capture
- Backgrounds. They're usually just matte paintings.
- Faces. It's much easier to draw an expression than to model a character
so that its surface patches can create that expression.
- Small simple animations. No modeling, no worries about lights, textures,
camera positions. That's one reason comic strips are still drawn.
- Making sure a character's feet don't slide when they walk.
Question 5 (20 points)
This synthesis question brings together some understandings of hierarchies
with a completely new idea: infinite recursive geometries, which they've
not really seen.
All of the hierarchies you've seen to date have been acyclic
trees. Your friend Flik suggests the following for a hierarchy:
- Why would you ever want such a crazy hierarchy? (i.e. what
objects would be represented nicely here?)
- What simple variable would you want to be able to add your
model and program to handle these objects?
- Fractal or recursive objects, such as a tree, fractal landscape, or
the model above.
- You'd want to be able to specify the depth of recursion for objects
(a number between 1 and infinity), as well as the depth of recursion your
system calculates for objects whose requested depth is infinite.
Question 6 (20 points)
This question tests whether they have acquired any evaluation skills
in the weekly crit sessions. What is shown will be a very rough animation
shown with lots of opportunity for constructive criticism.
In the corner video projector you'll see an animation looping
repeatedly. What are two comments you would suggest to the animator to have
them improve it? (i.e. what's wrong with it?)
To improve the animation, the animator could:
- Check the model again. There appear to be cracks in the geometry when
- Use more interesting textures. The default grey texture should never
- Use background images and floor planes. The black background should
never be seen.
- The pivot foot moves when the creature walks (the creature "travels"
in basketball terminology).
- Stabalize the camera. Just because you can put the camera on the head
of the mouse ("rodent-cam") doesn't mean you should. There's
too much jitter.
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