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btw, I was thinking about this and had to ask, why 70???


It's an empirical value ;-)
I was testing various framerate settings and this was the lowest one giving acceptable behavior in terms of penetration detection and speed (lower -> objects pass through each other, higher -> too slow).
Since ph_fps_maxlock is queried every frame you can set it to whichever value you like at any time. That it's transcendental does not matter since it's chopped off to 32-bit floating point anyway. What would make sense though is to pick a value that can be represented exactly in IEEE754, so that N iterations of stepsize 1/N does yield 1.0.