1. Framsticks physics © Szymon Ulatowski

2. Simulation goals Physics-based: create real-world feeling to intuitively understand behaviors Not necessarily very accurate but fast – performance matters

3. Building blocks „Parts” (atomic physical objects) „Joints” (description of internal forces and constraints, visualized as sticks) Environment (static objects, water)

4. Building blocks Part (position, velocity, mass,....) Environment Part (position, velocity, mass,....) Joint (joins related Parts)

5. Building blocks Part (position, velocity, mass,....) Environment Joint (joins related Parts) Part (position, velocity, mass,....) Joint originated force

6. Forces

7. Simulation step Determine all forces in the current state (t) Update velocity values for all objects (v t =v t-1 +F/m) Calculate new state (x t+1 =x t +v t )

8. Collisions Detection: Part  Environment (including ground and water) Part  Part (between different objects) Effects: Physical: controlled directly by the simulator User defined: can be handled by the experiment script

9. Environment Ground: flat, blocks or heightfield Water: –Buoyant force (effectively „cancels” gravity for creatures) –Resistance depending on the orientation (creatures can push themselves forward) Complex, dynamic environment: not directly, can be made of other simulator objects (interactions handled by the experiment script)

10. Environment

11. New in Framsticks v3: ODE Open Dynamics Engine, http://www.ode.org/http://www.ode.org/ Differences: Much more realistic True solid bodies with accurate collisions Rigid stick connections MechastickODE Partphysical pointimaginary point Joint (stick)imaginary linephysical body