Glitter: parameterize neighbor loop iterations

1 files changed, 18 insertions, 8 deletions

diff --git a/glitter.cginc b/glitter.cginc
index 022b176..0588446 100644
--- a/glitter.cginc
+++ b/glitter.cginc
@@ -169,9 +169,14 @@ float3 disk_to_ndf_ggx(float2 v_disk, float alpha) {
   return float3(alpha * hemi.xy, hemi.z) / denom;
 }
 
+float2 GlitterNeighborOffset(float index) {
+  return float2(frac(index * 0.5) * 2.0, floor(index * 0.5)) - 0.5;
+}
+
 // Algorithm 1 from Kemppinen et. al.
 float D_Kemppinen(float3 h, float alpha, float glint_alpha, float2 uv,
-    float2x2 uv_J, float N, float filter_size, out float3 micro_normal) {
+    float2x2 uv_J, float N, float filter_size, float angular_neighbor_count,
+    float spatial_neighbor_count, out float3 micro_normal) {
   float res = sqrt(N);
   float2 x_s = uv;
   float3 x_a_and_d = ndf_to_disk_ggx(h, alpha);
@@ -199,13 +204,13 @@ float D_Kemppinen(float3 h, float alpha, float glint_alpha, float2 uv,
 
     float2 base_i_a = clamp(round(x_a * res_a), 1, res_a-1);
     [loop]
-    for (uint j_a = 0; j_a < 4; ++j_a) {
-      float2 i_a = base_i_a + float2(int2(j_a, j_a/2)%2)-.5;
+    for (float j_a = 0.0; j_a < angular_neighbor_count; j_a += 1.0) {
+      float2 i_a = base_i_a + GlitterNeighborOffset(j_a);
 
       float2 base_i_s = round(x_s * res_s);
       [loop]
-      for (uint j_s = 0; j_s < 4; ++j_s) {
-        float2 i_s = base_i_s + float2(int2(j_s, j_s/2)%2)-.5;
+      for (float j_s = 0.0; j_s < spatial_neighbor_count; j_s += 1.0) {
+        float2 i_s = base_i_s + GlitterNeighborOffset(j_s);
 
         float2 g_s = (i_s + Rand2D(i_s, i_a, l, 1u) - .5) / res_s;
         float2 g_a = (i_a + Rand2D(i_s, i_a, l, 2u) - .5) / res_a;
@@ -241,6 +246,7 @@ struct LightGlitter {
 // Glitter data getter to be run from lighting code.
 LightGlitter GetGlitterLighting(
     float glitter_amount, float glitter_roughness,
+    float glitter_spatial_neighbor_count, float glitter_angular_neighbor_count,
     float2 uv, float3x3 tbn, float roughness,
     float3 normal, float3 V, float3 direct_H, float3 indirect_dir) {
   LightGlitter g;
@@ -252,19 +258,23 @@ LightGlitter GetGlitterLighting(
   float3 direct_H_tangent = mul(direct_H, transpose(tbn));
   float3 direct_micro_normal;  // unused
   g.direct_D = D_Kemppinen(direct_H_tangent, roughness, glitter_roughness,
-      uv, uv_J, N, glitter_filter_size, direct_micro_normal);
+      uv, uv_J, N, glitter_filter_size,
+      glitter_angular_neighbor_count, glitter_spatial_neighbor_count,
+      direct_micro_normal);
 
   // Indirect
   float3 indirect_H = normalize(V + indirect_dir);
   float3 indirect_H_tangent = mul(indirect_H, transpose(tbn));
   float3 indirect_micro_normal;  // unused, but required by D_Kemppinen
   g.indirect_D = D_Kemppinen(indirect_H_tangent, roughness, glitter_roughness,
-      uv, uv_J, N, glitter_filter_size, indirect_micro_normal);
+      uv, uv_J, N, glitter_filter_size,
+      glitter_angular_neighbor_count, glitter_spatial_neighbor_count,
+      indirect_micro_normal);
   g.indirect_NoL = max(1e-4, dot(normal, indirect_dir));
   g.indirect_LoH = max(1e-4, dot(indirect_dir, indirect_H));
 
   return g;
 }
-#endif
+#endif  // _GLITTER
 
 #endif  // __GLITTER_INC