Physics simulation fixed time step and enhanced determinism settings, pull request

[B1TZ3R0]

@0lento;717053

There’s also another thing that throws the determinism off and it’s in the substepping code itself. The line that will throw the determinism off is here:
https://github.com/AndreaCatania/UnrealEngine/blob/4c724f2b2c114a39c7580f765a6d08bfd29f82d9/Engine/Source/Runtime/Engine/Private/PhysicsEngine/PhysSubstepTasks.cpp#L389

and this is how I solved it:
https://github.com/0lento/UnrealEngine/blob/121687a4a853836b494874c6817fcfe8a123849a/Engine/Source/Runtime/Engine/Private/PhysicsEngine/PhysSubstepTasks.cpp#L423

The issue is that while the math is right, since it’s floats we are talking about that value will have precision issues if you run the project at low framerates where you get a lot of substeps. Since fixed timesteps don’t need that math anyway, you can just assign the same subtime for the last substep anyway.

Very nice hint, I’ve added it: https://github.com/AndreaCatania/UnrealEngine/blob/f864b778e13f4fb67ab567f689db1223c01cb587/Engine/Source/Runtime/Engine/Private/PhysicsEngine/PhysSubstepTasks.cpp#L389

I also moved enhanced determinism setting into advanced section.

Do you have another advices about determinism PhysX?