I read the documentation and could not find the formulas for force calculation. I could only find the following information at the Advanced Collision Detection section of the docs:

The generation of contact points does not however mean that a large impulse will immediately be applied at these locations to separate the shapes, or to even prevent further motion in the direction of penetration. This would make the simulation jitter unless the simulation time step is selected to be tiny, which is not desirable for real time performance. Instead, we want the force at the contact to smoothly increase as penetration increases until it reaches a value sufficiently high to stop any further penetrating motion. The distance at which this maximum force is reached is the restDistance, because at this distance two shapes stacked on each other will reach static equilibrium and come to rest. When the shapes are for some reason pushed together so much that they have a distance below restDistacnce, an even greater force is applied to push them apart until they are at restDistance again. The variation of force applied as the distance changes is not necessarily linear, but it is smooth and continuous which results in a pleasing simulation even at large time steps.

I would like to find a formula for such forces.

- Is the formula of calculation of the forces exerted by objects that are pushed apart available?
- Is it the same formula used by simulated force/torque sensors?
- Are calculations for PhysX 4 and 5 performed in the same manner for penetrating rigid bodies?

The purpose of these questions is to evaluate manipulation experiments with robotic grippers. Interactions between the gripper and grabbed objects are usually difficult to approximate to the real world.