fixes and tweaks for surface models

All surface models including ``SURFACE_COMPLEX`` and ``SURFACE_WLS`` are now working. Note that the WLS won't work right in hybrid rendering mode since that mode relies on matching up incoming and outgoing photon wavelengths in a lookup table.

4 files changed, 26 insertions, 6 deletions

diff --git a/chroma/cuda/geometry_types.h b/chroma/cuda/geometry_types.h
index ab54dfa..f82f372 100644
--- a/chroma/cuda/geometry_types.h
+++ b/chroma/cuda/geometry_types.h
@@ -30,13 +30,10 @@ struct Surface
     float *reflect_specular;
     float *eta;
     float *k;
-
-    float *reemission_wavelength;
     float *reemission_cdf;
 
     unsigned int model;
     unsigned int n;
-    unsigned int reemission_n;
     unsigned int transmissive;
     float step;
     float wavelength0;
diff --git a/chroma/cuda/hybrid_render.cu b/chroma/cuda/hybrid_render.cu
index 29edefa..2c64d0e 100644
--- a/chroma/cuda/hybrid_render.cu
+++ b/chroma/cuda/hybrid_render.cu
@@ -44,6 +44,9 @@ to_diffuse(Photon &p, State &s, Geometry *g, curandState &rng, int max_steps)
 	    if (p.history & REFLECT_DIFFUSE)
 		break;
 
+            if (p.history & SURFACE_REEMIT)
+                break;
+
 	    if (command == BREAK)
 		break;
 
diff --git a/chroma/cuda/photon.h b/chroma/cuda/photon.h
index 68ea92c..09430e9 100644
--- a/chroma/cuda/photon.h
+++ b/chroma/cuda/photon.h
@@ -493,7 +493,7 @@ propagate_complex(Photon &p, State &s, curandState &rng, Surface* surface, bool
         return BREAK;
     }
     else if (uniform_sample < absorb + reflect) {
-        return propagate_at_specular_reflector(p, s);
+        return propagate_at_diffuse_reflector(p, s, rng);
     }
     else {
         // transmit
@@ -515,7 +515,7 @@ propagate_at_wls(Photon &p, State &s, curandState &rng, Surface *surface, bool u
     float uniform_sample = curand_uniform(&rng);
 
     if (use_weights && p.weight > WEIGHT_LOWER_THRESHOLD && absorb < (1.0f - WEIGHT_LOWER_THRESHOLD)) {
-         // Prevent absorption and reweight accordingly
+        // Prevent absorption and reweight accordingly
         float survive = 1.0f - absorb;
         absorb = 0.0f;
         p.weight *= survive;
@@ -528,7 +528,7 @@ propagate_at_wls(Photon &p, State &s, curandState &rng, Surface *surface, bool u
         float uniform_sample_reemit = curand_uniform(&rng);
         if (uniform_sample_reemit < reemit) {
             p.history |= SURFACE_REEMIT;
-            p.wavelength = sample_cdf(&rng, surface->reemission_n, surface->reemission_wavelength, surface->reemission_cdf);
+            p.wavelength = sample_cdf(&rng, surface->n, surface->wavelength0, surface->step, surface->reemission_cdf);
             return propagate_at_diffuse_reflector(p, s, rng); // reemit isotropically (eh?)
         }
 
diff --git a/chroma/cuda/random.h b/chroma/cuda/random.h
index e9d2e75..ee528ea 100644
--- a/chroma/cuda/random.h
+++ b/chroma/cuda/random.h
@@ -44,6 +44,26 @@ sample_cdf(curandState *rng, int ncdf, float *cdf_x, float *cdf_y)
     return cdf_x[lower] * frac + cdf_x[upper] * (1.0f - frac);
 }
 
+// Sample from a uniformly-sampled CDF
+__device__ float
+sample_cdf(curandState *rng, int ncdf, float x0, float delta, float *cdf_y)
+{
+    float u = curand_uniform(rng);
+
+    int lower = 0;
+    int upper = ncdf - 1;
+    while(lower < upper-1) {
+	int half = (lower + upper) / 2;
+	if (u < cdf_y[half])
+	    upper = half;
+	else
+	    lower = half;
+    }
+  
+    float frac = (u - cdf_y[lower]) / (cdf_y[upper] - cdf_y[lower]);
+    return (x0 + delta * lower) * frac + (x0 + delta * upper) * (1.0f - frac);
+}
+
 extern "C"
 {