LiquidFun uses several approximations to simulate rigid body physics efficiently. This brings some limitations.
Here are the current limitations:
- Stacking heavy bodies on top of much lighter bodies is not stable. Stability degrades as the mass ratio passes 10:1.
- Chains of bodies connected by joints may stretch if a lighter body is supporting a heavier body. For example, a wrecking ball connect to a chain of light weight bodies may not be stable. Stability degrades as the mass ratio passes 10:1.
- There is typically around 0.5cm of slop in shape versus shape collision.
- Continuous collision does not handle joints. So you may see joint stretching on fast moving objects.
- LiquidFun uses the symplectic Euler integration scheme. It does not reproduce parabolic motion of projectiles and has only first-order accuracy. However it is fast and has good stability.
- LiquidFun uses an iterative solver to provide real-time performance. You will not get precisely rigid collisions or pixel perfect accuracy. Increasing the iterations will improve accuracy.