Physics-Inspired Upsampling for Cloth Simulation in Games

1. Physics-Inspired Upsampling for Cloth Simulation in Games Paper by: LadislavKavan - Disney Interactive Studios Dan Gerszewski - Disney Interactive Studios - University of Utah Adam W. Bargteil - University of Utah Peter-Pike Sloan - Disney Interactive Studios

2. Overview The authors propose a method for learning up-sampling operators for a physically based cloth simulations for games. This is in contract to classical subdivision schemes. They claim that their method can adapt to specific context, which allows a higher detail to be rendered than subdivision.

3. Overview Cloth simulations in games are becoming more popular due to it’s availability in game engines such as PhysX™, Havok™ and the open-source Bullet Physics Library. This is in contract to the common practice of using pre-computed solutions. These have limited flexibility and aren’t well suited for novel material motions.

4. Fabric Examples In this figure, you can see examples of (a) Coarse simulation, (b) subdivision, (c) their proposed up-sampling and (d) fine-scale simulation

5. Limitations In contrast to subdivision, they consider dense up-sampling matrices that are specialized for a given context. This is justified because in games, interactions are limited by design. (i.e. flags are always flown on poles, etc…)

6. Subdivision One of the problems with subdivision is that this method only guarantees surface smoothness. It has no information about the material properties or external forces. Their method takes those concepts into consideration when creating their model.

7. Oscillatory Modes One of the interesting things their model can do is introduce oscillatory modes into the simulation. As you can see, the right hand model has more detail than the un-sampled left hand model, which has no oscillatory modes.

8. Other Limitations One of the other limitations of this model mentioned is cloth self-collisions. This model doesn’t handle them because of performance considerations. Also, this model isn’t suitable for higher resolution simulations for the same performance reason – the computations are prohibitively expensive.

9. Conclusion The video they made clearly shows that their method for simulating cloth is very believable. They also claim that their model can be useful for other things such as hand, facial and hair animations. Overall, their method does seem to fill the gap between very fast, non-physical subdivision and more complex non-linear deformers, like they claim.