What is Global CFM and Global ERP

[MutantPixel]

Hi all,
I'm trying to understand what Global CFM and Global ERP are, does anyone have even some simple definitions of what these are and/or what they do? I figured out that CFM stands for 'Constraint Force Mixing', but that doesn't help much. Thanks!
-james

[Erwin Coumans]

they are tweaking values for the constraint solver.

The word 'Global' means that those values apply to all constraints, rather then local values that only apply to specific constraints. The CFM, constraint force mixing, adds some small value to the main diagonal of the constraint matrix, to avoid degenerate matrices. The ERP, error reduction parameter, is a rate of how fast the error is reduced.

You might want to read up more on this in Erin Catto's recent GDC presentation.

Thanks,
Erwin

[MutantPixel]

Thank you very much, that helps a lot.
--james