  We present a fast and efficient method for intersecting rays with
Catmull-Clark subdivision surfaces. It takes advantage of the approximation
democratized by OpenSubdiv, in which regular patches are represented by tensor
product B\'ezier surfaces and irregular ones are approximated using Gregory
patches. Our algorithm operates solely on the original patch data and can
process both patch types simultaneously with only a small amount of control
flow divergence. Besides introducing an optimized method to determine axis
aligned bounding boxes of Gregory patches restricted in the parametric domain,
several techniques are introduced that accelerate the recursive subdivision
process including stackless operation, efficient work distribution, and control
flow optimizations. The algorithm is especially useful for quick turnarounds
during patch editing and animation playback.
