The friction coefficients will be updated by an existing pull request, changes have been made to use mu of 0.9 for atlas feet. This value may change when we get more realistic friction coefficient approximations.
fdir1 is a Vector3 specifying the direction of mu1 in the collision local reference frame. If left unspecified as (0, 0, 0), mu1 and mu2 will align along x and y-axis of the world reference frame. In the atlas case, the fdir1 is specified to be (1, 0, 0), so mu1 will always act along the "heel-to-toe" direction.
The friction coefficients will be updated by an existing pull request, changes have been made to use mu of 0.9 for atlas feet. This value may change when we get more realistic friction coefficient approximations.