Hi, Could someone explain why the MERGECONTACTS case in collision_trimesh_sphere.cpp (approx line 375-378) does: // Remember to divide in square space. Contact->depth = dSqrt(dDOT(Contact->normal, Contact->normal) / OutTriCount); And not: Contact->depth = dSqrt(dDOT(Contact->normal, Contact->normal)) / OutTriCount; Thanks, Vadim.