Function OBJMaterial__sample

tutorials/pathtracer/pathtracer_device.cpp:573–633

}

Vec3fa OBJMaterial__sample(ISPCOBJMaterial* material, const BRDF& brdf, const Vec3fa& Lw, const Vec3fa& wo, const DifferentialGeometry& dg, Sample3f& wi_o, Medium& medium, const Vec2f& s)
{
  Vec3fa cd = Vec3fa(0.0f);
  Sample3f wid = make_Sample3f(Vec3fa(0.0f),0.0f);
  if (max(max(brdf.Kd.x,brdf.Kd.y),brdf.Kd.z) > 0.0f) {
    wid = cosineSampleHemisphere(s.x,s.y,dg.Ns);
    cd = float(one_over_pi) * clamp(dot(wid.v,dg.Ns)) * brdf.Kd;
  }

  Vec3fa cs = Vec3fa(0.0f);
  Sample3f wis = make_Sample3f(Vec3fa(0.0f),0.0f);
  if (max(max(brdf.Ks.x,brdf.Ks.y),brdf.Ks.z) > 0.0f)
  {
    const Sample3f refl = make_Sample3f(reflect(wo,dg.Ns),1.0f);
    wis.v = powerCosineSampleHemisphere(brdf.Ns,s);
    wis.pdf = powerCosineSampleHemispherePDF(wis.v,brdf.Ns);
    wis.v = frame(refl.v) * wis.v;
    cs = (brdf.Ns+2) * float(one_over_two_pi) * powf(max(dot(refl.v,wis.v),1e-10f),brdf.Ns) * clamp(dot(wis.v,dg.Ns)) * brdf.Ks;
  }

  Vec3fa ct = Vec3fa(0.0f);
  Sample3f wit = make_Sample3f(Vec3fa(0.0f),0.0f);
  if (max(max(brdf.Kt.x,brdf.Kt.y),brdf.Kt.z) > 0.0f)
  {
    wit = make_Sample3f(neg(wo),1.0f);
    ct = brdf.Kt;
  }

  const Vec3fa md = Lw*cd/wid.pdf;
  const Vec3fa ms = Lw*cs/wis.pdf;
  const Vec3fa mt = Lw*ct/wit.pdf;

  const float Cd = wid.pdf == 0.0f ? 0.0f : max(max(md.x,md.y),md.z);
  const float Cs = wis.pdf == 0.0f ? 0.0f : max(max(ms.x,ms.y),ms.z);
  const float Ct = wit.pdf == 0.0f ? 0.0f : max(max(mt.x,mt.y),mt.z);
  const float C  = Cd + Cs + Ct;

  if (C == 0.0f) {
    wi_o = make_Sample3f(Vec3fa(0,0,0),0);
    return Vec3fa(0,0,0);
  }

  const float CPd = Cd/C;
  const float CPs = Cs/C;
  const float CPt = Ct/C;

  if (s.x < CPd) {
    wi_o = make_Sample3f(wid.v,wid.pdf*CPd);
    return cd;
  }
  else if (s.x < CPd + CPs)
  {
    wi_o = make_Sample3f(wis.v,wis.pdf*CPs);
    return cs;
  }
  else
  {
    wi_o = make_Sample3f(wit.v,wit.pdf*CPt);