Physics Settings
The physics settings include a number of properties that can be used to control global physics-related settings.
Timestep
The physics timestep is the discrete length of time for each physics frame. The simulation is advanced in discrete time slices or frames. Reducing the timestep can improve the accuracy and stability of the simulation, but reduces the maximum speed at which the simulation can run. It may be necessary to reduce the timestep if you want to simulate small parts or fast-moving machines. You can try manually stepping through the simulation, one timestep at a time, to see how far any rigid bodies move in a single timestep. If the distances are not small relative to the size of the collision geometry, then you should reduce the timestep.
Solver
The solver is used to solve all physics constraints. The default solver is Projected Gauss-Seidel (PGS), which provides a good balance of convergence speed and general stability.
Default Static Friction
The default static friction coefficient for all colliders that have not been assigned a physics material.
Default Dynamic Friction
The default dynamic friction coefficient for all colliders that have not been assigned a physics material.
Default Restitution
The default restitution coefficient for all colliders that have not been assigned a physics material.
Bounce Threshold
The relative velocity below which the restitution coefficient is assumed to be zero. Using a non-zero value improves the stability of the simulation by preventing small oscillations.
Depenetration Velocity
The maximum separation velocity to use when resolving penetrating rigid bodies. Using a high value will resolve penetrations more quickly, resulting in harder contacts, but can introduce instability. Lower values cause collisions to be resolved over multiple frames, resulting in softer contacts and improving stability for stacks of boxes.
Position Iterations
The number of solver iterations to use for resolving constraint positional/geometric error. The default value is 16, which is a good balance between accuracy and performance. A higher number of solver iterations may be required for interactions between rigid bodies with large mass ratios, stacks of boxes, or for machines with many joints. If you see the joints breaking apart, try doubling the number of position iterations until the simulation becomes stable. The maximum number of position iterations that can be used is 255.
Velocity Iterations
The number of solver iterations to use for correcting any energy introduced by solving the constraints for positional/geometric error. The default value is 2, which generally corrects most of the energy introduced. It usually isn’t necessary to increase the velocity iterations. The maximum number of velocity iterations that can be used in 255.