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C H A P T E R 8
Controlling Cloth Simulations
“F D da, Director Approval”
David Eberle
Twist on Newton’s second law to indicate the high level of art direction in feature film produc-
tion.
Beyond the Basics
is is definitely a somewhat more advanced topic but it’s just too interesting not to mention it.
8.1 INTRODUCTION
Wojtan et al. [2006] discovered that cloth simulations can be controlled to reach certain reference
positions or velocities at some time or multiple times in the simulation. As a computer graphics
enthusiast, this should get you excited!
Most of the time, we’re not just interested in realistically simulating garments. We prob-
ably want to have some control over the result so that we can express our creative vision. is is
definitely the case for highly art directed animated movies where we don’t want to just truthfully
recreate physics but also want to have fine-grained control over the final look.
Let’s say you’re directing an animated movie and you want the clothes to look a certain
way. For instance, you want the garment to have a very specific silhouette at one crucial instant
in time. You can’t really rely on the simulator to automatically give you what you want.
One way to do this might be to add specific wind forces over time that hopefully will blow
the cloth in exactly the right shape at exactly the right time. But, this seems kind of hard too. If
it is ever going to work at all, at the very least, it would require a lot of trial-and-error involving
long computations for every trial run. is is a very frustrating workflow for artists.
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