Bodies of creatures are divided into small pieces (at sticks' ends) which are ideal material points. This approach is called "finite element method": not every point of a material body is simulated – only a finite number of points, representing small volumes in the body. The simulator calculates all the forces affecting a given point: gravity, elastic reaction when joined with other points, ground reaction and friction when touching the ground, etc.
In our model some assumptions are taken to simplify calculations. A primitive but fast numeric integration method is used, so the results are not very exact when dealing with big forces.
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The picture on the right shows sample forces calculated in the Framsticks physical simulator, Mechastick. The body is made from parts (points) and joints (sticks, rods). |
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Another simulation engine that can be used within Framsticks is ODE.
More details on simulation is here.