Why bullet proposes value to clamp number of substeps?

[Yola]

Why bullet needs maxSubSteps at all? Why to clamp value at all? In the code i saw the following comment:

Code: Select all

    //clamp the number of substeps, to prevent simulation grinding spiralling down to a halt
    int clampedSimulationSteps = (numSimulationSubSteps > maxSubSteps) ? maxSubSteps : numSimulationSubSteps;

What does it mean?

simulation grinding spiralling down

[drleviathan]

There is a phenomenon known as the "physics simulation spiral of death" where the real time to compute the world's next state is larger than the timestep itself. On each step the simulation falls further behind. This can happen when the world has too many objects or the objects are too complex. A simple way to exit the spiral is to clamp the number of substeps.