Error if the unit of CoP is mm in grf.mot

[Tian-A-Tan]

nimblephysics/dart/biomechanics/DynamicsFitter.cpp

Lines 9656 to 9661 in bf5c5a1

	// Add 20cm to each side, to be very conservative
	s_t padding = 0.20;
	minX -= padding;
	maxX += padding;
	minZ -= padding;
	maxZ += padding;

Close this issue if I'm wrong but my understanding of DynamicFitter is that it can adapt to .mot files with different CoP units (e.g., mm or m). However, I encountered "Marking trial 0, timestep xxx as probably missing GRF, due to contact heuristic" warning by using mm as CoP unit, probably because the above "padding" is in m.

[nickbianco]

@TheOne-1 I believe COP information is converted to meters before this step, although after checking OpenSimParser::loadGRF, I wasn't able to confirm this.

@keenon, do you know if we convert to meters somewhere else?