When the brush size is bigger than the entire mesh, fdata.tot_co can be 0, so the pose origin will default to (0,0,0), which does not make much sense. After this patch, the pose origin will be set to the farthest vertex from the pose origin, which at least should be in the surface of the mesh and in most cases in the direction the pose brush was already detecting the origin. Reviewed By: sergey Differential Revision: https://developer.blender.org/D7773