The bodies of creatures are divided into small pieces (at sticks' ends) which are ideal material points. This approach is called the "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 acting on 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 made to simplify calculations. A simple and fast numeric integration method is used, so the results are not very exact when dealing with large forces.
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The picture on the right shows sample forces calculated in the Framsticks physics simulator, Mechastick. The body is composed of parts (points) and joints (sticks, rods). |
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Another simulation engine that can be used within Framsticks is ODE.