CSE557 Project, Winter 2000
Cartoon Physics

General Description

We design a simulation environment that combines typical behaviors of cartoon characters and traditional simulations of Newtonian physics. There are several rules that cartoon characters have to obey when they move:

LAW 100: Any body suspended in space will remain in space until made aware of its situation.

LAW 101: When any body is in motion, the butt part will be more reluctant to move than other parts of the body.

LAW 102: ny body colliding into a wall will stick on it as a flat shape conforming to its perimeter.

Corollary: Any body run over by a car will become flat as a piece of paper for a few moments. If luckily enough that it's not blew off by wind, it will go back to the original shape without any damage.

References

We referred to a paper titled "Faking Dynamics of Ropes and Springs" by Ronen Barzel at Pixar Animation Studio which discusses how ropes and springs can be animated realistically enough without using pure physical simulation (this technique was used in producing the Slinky Dog in Toy Story).

How It Is Different From Existing Work

Our work is similar in spirit to this paper in that they are both trying to find a good compromise between pure physics and approximation in animating cartoon characters. However, our work is fundamentally different from what was done in this paper because we are trying to achieve cartoon-like behavior based on physics, while the paper tries to achieve realism with as little physics as possible by using cheaper and yet reasonable approximations. In contrast, we try to approximate unrealistic, exaggerated cartoon behaviors by manipulating various physical parameters in a way that is impossible in reality (for example, changing material properties over time).

Detailed Description

Available as a separate document: in either .pdf or .ps format (PostScript version has much better quality, though).

Results

The result of the project is well summarized in this sample movie, our artifact.

The executable and example models can also be downloaded:

• animator.exe - we used the same animator we had built for the previous project (don't forget to download modeler.dll and put it in the same directory).
• inertia-gravity.dll - the example for experimenting with inertia and gravity. Several parameters are adjustable such as the starting and ending point of motion, the masses of different body portions, the amount of inertia, etc.
• collision-wall.dll - the collision example. You can select between real and cartoon physics.
• collision-car.dll - the second (and incomplete) collision example. No parameters available, although the sliders are all there.