old_contents: import numpy as np
  import volpy
  from libbenchmark import render, get_parser
  
  CENTER = np.array([0, 0, 2.5, 1])
  RADIUS = 1.0
  RED = (1, 0, 0)
  BLUE = (0, 0, 1)
  
  
  def sphere(x):
      norms = np.linalg.norm(x - CENTER, axis=1)
      return np.where(norms < RADIUS, 1, 0)
  
  
  def sphere_color(x):
      siny = np.sin(45 * x[:, 1])
      mask = np.sin(siny + 45 * x[:, 0]) > 0
      mask = mask.reshape(len(mask), 1)
      return mask * RED + (1 - mask) * BLUE
  
  
  def main():
      parser = _get_parser()
      args = parser.parse_args()
  
      if args.color:
          ambient_color = sphere_color
      else:
          ambient_color = None
  
      element = volpy.Element(sphere, ambient_color)
      scene = volpy.Scene(ambient=element, scatter=args.scatter)
      image = render(scene, args)
      image.save(args.output)
  
  
  def _get_parser():
      parser = get_parser()
      parser.add_argument('-o', '--output', default='out.png')
      parser.add_argument('-c', '--color', action='store_true')
      parser.add_argument('-k', '--scatter', type=float, default=10)
      return parser
  
  if __name__ == '__main__':
      main()
  
new_contents: import numpy as np
  import volpy
  from libbenchmark import render, get_parser
  
  CENTER = np.array([0, 0, 2.5, 1])
  RADIUS = 1.0
  RED = (1, 0, 0)
  BLUE = (0, 0, 1)
  
  
  def sphere(x):
      norms = np.linalg.norm(x - CENTER, axis=1)
      return np.where(norms < RADIUS, 1, 0)
  
  
  def sphere_color(x):
      siny = np.sin(45 * x[:, 1])
      mask = np.sin(siny + 45 * x[:, 0]) > 0
      mask = mask.reshape(len(mask), 1)
      return mask * RED + (1 - mask) * BLUE
  
  
  def plane_light(x):
      f = x[:, 1] / 2
      return np.where(f > 0, f, 0)
  
  
  def main():
      parser = _get_parser()
      args = parser.parse_args()
  
      element = volpy.Element(sphere)
      if args.color:
          element.color = sphere_color
  
      scene = volpy.Scene(scatter=args.scatter)
      if args.diffuse:
          scene.diffuse = element
          scene.lights.append(volpy.Light(plane_light))
      else:
          scene.ambient = element
  
      image = render(scene, args)
      image.save(args.output)
  
  
  def _get_parser():
      parser = get_parser()
      parser.add_argument('-o', '--output', default='out.png')
      parser.add_argument('-c', '--color', action='store_true')
      parser.add_argument('-k', '--scatter', type=float, default=10)
      parser.add_argument('-D', '--diffuse', action='store_true')
      return parser
  
  if __name__ == '__main__':
      main()
  
subject: test diffuse in benchmark implicit function script