   Comparing rotations with different 0 pnt
  Seems like a simple problem, but somehow a logical solution escapes me.I want to compare mulitple different rotational systems against eachother, they all have different rest points (where their rotation is 0). The resting position of one may be at 90, while the others is at 180.  Problem is I can't simply subtract 90 or 180 to negate the difference because then they wouldn't go from 0-360 anymore, but from 270 to -90 etc.How can I compare rotations that don't have their 0 points aligned?I need to align them without changing their range.   
  Does something like this help?float WrapRangeTo_0_360( float a ){  while( a > 360 )    a -= 360;  while( a < 0 )    a += 360;  return a;}