code: def arcball_map_to_sphere(point, center, radius):
      """Return unit sphere coordinates from window coordinates."""
      v0 = (point[0] - center[0]) / radius
      v1 = (center[1] - point[1]) / radius
      n = v0 * v0 + v1 * v1
      if n > 1.0:
          # position outside of sphere
          n = math.sqrt(n)
          return numpy.array([v0 / n, v1 / n, 0.0])
      else:
          return numpy.array([v0, v1, math.sqrt(1.0 - n)])
  
imports: import math
  import numpy
label_desc: Use image node_id 35 for calling a global function with example usage: arcball_map_to_sphere(point, center, radius) and returns: numpy, numpy