Walking Mushroom (Mpeg-1 movie, 406404 Bytes).
Walking Mushroom (Mpeg-1 movie, 406404 Bytes).
The walking mushroom was animated by moving four points on the base of the mushroom in the same way as was done for the walking knight , and the walking teapot . In addition we contracted the shape points on the back of the stem to tilt the cap of the mushroom back so that it could "see" where it was going while it was walking. Again we get nice secondary motion generated automatically by the physical simulation.
Falling Mushroom (Mpeg-1 movie, 252284 Bytes).
Close-up showing deformation due to drag forces
(Mpeg-1 movie, 241940 Bytes).
This example is a simple animation of a mushroom falling through the air to highlight the aerodynamic effects that are created by the viscous forces which are a part of our physical model. The cap and stem of the mushroom are initially held together by four attachment constraints, as they were for the walking animation. Part way through the animation we release the attachment constraints. We have given the cap a much lower density than the stem. This, together with its greater surface area causes it to be more affected by the viscous forces of the surrounding medium than the stem.
While they are attached, the cap acts as a parachute of sorts for the heavier stem. The drag forces on the cap along with the weight of the attached stem also cause the cap to deform. After the two parts are separated the cap moves in a gentle downward spiral while the stem continues to drop in a relatively straight line at an accelerated rate. This clearly shows the relative masses of the two parts. The spiraling motion of the cap is only possible using viscous forces that are related to the surface geometry of the object.
The original model of the mushroom was created by Wayne Carlson and is (c) Ohio State University. It was taken from an Inventor data file distributed with Silicon Graphics computer systems.
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