Suspicious conditional found by PVS-Studio T48917 Original code (from Blender’s initial open-source commit!) looks like it’s testing inputs to atan2f, to avoid undefined function values. Passing xn=0 does *not* always evaluate to 0 though… I’m not sure if this is a coding error or was done for a desired visual result. Also changed xn==0 to xn>=0 to avoid function call in more cases. Good description and visualization of atan2f function: http://en.cppreference.com/w/c/numeric/math/atan2