/*  simple_occlusion
*
*  by Andrew Osiow 
*  from the RenderMan App. Notes #35
*/

normal shadingnormal(normal N)
{
    normal Ns = normalize(N);
    uniform float sides = 2;
    uniform float raydepth;
    attribute("Sides", sides);
    rayinfo("depth", raydepth);
    if (sides == 2 || raydepth > 0)
	Ns = faceforward(Ns, I, Ns);
    return Ns;
}

surface simple_occlusion(float samples = 64, maxvariation = 0.02)
{
    normal Ns = shadingnormal(N); // normalize N and flip it if backfacing

   // Compute occlusion
    float occ = occlusion(P, Ns, samples, "maxvariation", maxvariation);
       
   // Set Ci and Oi
    Ci = (1 - occ) * Cs * Os;
    Oi = Os;
}