Cleanup: EEVEE: Remove hammersley texture and split hammersley code

5 files changed, 86 insertions, 65 deletions

diff --git a/source/blender/draw/engines/eevee/shaders/bsdf_sampling_lib.glsl b/source/blender/draw/engines/eevee/shaders/bsdf_sampling_lib.glsl
index c190ca0e245..7ce95a4aff2 100644
--- a/source/blender/draw/engines/eevee/shaders/bsdf_sampling_lib.glsl
+++ b/source/blender/draw/engines/eevee/shaders/bsdf_sampling_lib.glsl
@@ -1,32 +1,14 @@
 
+/**
+ * Sampling distribution routines for Monte-carlo integration.
+ **/
+
 #pragma BLENDER_REQUIRE(common_math_geom_lib.glsl)
 #pragma BLENDER_REQUIRE(bsdf_common_lib.glsl)
 
-uniform sampler1D texHammersley;
-
-vec3 tangent_to_world(vec3 vector, vec3 N, vec3 T, vec3 B)
-{
-  return T * vector.x + B * vector.y + N * vector.z;
-}
-
-vec3 world_to_tangent(vec3 vector, vec3 N, vec3 T, vec3 B)
-{
-  return vec3(dot(T, vector), dot(B, vector), dot(N, vector));
-}
-
-#ifdef HAMMERSLEY_SIZE
-vec3 hammersley_3d(float i, float invsamplenbr)
-{
-  vec3 Xi; /* Theta, cos(Phi), sin(Phi) */
-
-  Xi.x = i * invsamplenbr;
-  Xi.yz = texelFetch(texHammersley, int(i), 0).rg;
-
-  return Xi;
-}
-#endif
-
-/* -------------- BSDFS -------------- */
+/* -------------------------------------------------------------------- */
+/** \name Microfacet GGX distribution
+ * \{ */
 
 #define USE_VISIBLE_NORMAL 1
 
@@ -89,12 +71,18 @@ vec3 sample_ggx(vec3 rand, float alpha, vec3 V, vec3 N, vec3 T, vec3 B, out floa
   return tangent_to_world(Ht, N, T, B);
 }
 
-float pdf_hemisphere()
+/** \} */
+
+/* -------------------------------------------------------------------- */
+/** \name Uniform Hemisphere
+ * \{ */
+
+float pdf_uniform_hemisphere()
 {
   return 0.5 * M_1_PI;
 }
 
-vec3 sample_hemisphere(vec3 rand)
+vec3 sample_uniform_hemisphere(vec3 rand)
 {
   float z = rand.x;                      /* cos theta */
   float r = sqrt(max(0.0, 1.0 - z * z)); /* sin theta */
@@ -103,45 +91,33 @@ vec3 sample_hemisphere(vec3 rand)
   return vec3(x, y, z);
 }
 
-vec3 sample_hemisphere(vec3 rand, vec3 N, vec3 T, vec3 B, out float pdf)
+vec3 sample_uniform_hemisphere(vec3 rand, vec3 N, vec3 T, vec3 B, out float pdf)
 {
-  vec3 Ht = sample_hemisphere(rand);
-  pdf = pdf_hemisphere();
+  vec3 Ht = sample_uniform_hemisphere(rand);
+  pdf = pdf_uniform_hemisphere();
   return tangent_to_world(Ht, N, T, B);
 }
 
-#ifdef HAMMERSLEY_SIZE
-vec3 sample_ggx(float nsample,
-                float inv_sample_count,
-                float alpha,
-                vec3 V,
-                vec3 N,
-                vec3 T,
-                vec3 B,
-                out float pdf)
-{
-  vec3 Xi = hammersley_3d(nsample, inv_sample_count);
-  return sample_ggx(Xi, alpha, V, N, T, B, pdf);
-}
+/** \} */
 
-vec3 sample_hemisphere(
-    float nsample, float inv_sample_count, vec3 N, vec3 T, vec3 B, out float pdf)
-{
-  vec3 Xi = hammersley_3d(nsample, inv_sample_count);
-  return sample_hemisphere(Xi, N, T, B, pdf);
-}
+/* -------------------------------------------------------------------- */
+/** \name Uniform Cone sampling
+ * \{ */
 
-vec3 sample_cone(float nsample, float inv_sample_count, float angle, vec3 N, vec3 T, vec3 B)
+vec3 sample_uniform_cone(vec3 rand, float angle)
 {
-  vec3 Xi = hammersley_3d(nsample, inv_sample_count);
-
-  float z = cos(angle * Xi.x);           /* cos theta */
+  float z = cos(angle * rand.x);         /* cos theta */
   float r = sqrt(max(0.0, 1.0 - z * z)); /* sin theta */
-  float x = r * Xi.y;
-  float y = r * Xi.z;
-
-  vec3 Ht = vec3(x, y, z);
+  float x = r * rand.y;
+  float y = r * rand.z;
+  return vec3(x, y, z);
+}
 
+vec3 sample_uniform_cone(vec3 rand, float angle, vec3 N, vec3 T, vec3 B)
+{
+  vec3 Ht = sample_uniform_cone(rand, angle);
+  /* TODO pdf? */
   return tangent_to_world(Ht, N, T, B);
 }
-#endif
+
+/** \} */
diff --git a/source/blender/draw/engines/eevee/shaders/lightprobe_filter_diffuse_frag.glsl b/source/blender/draw/engines/eevee/shaders/lightprobe_filter_diffuse_frag.glsl
index 18fcfd4fd41..9ecc50d9df5 100644
--- a/source/blender/draw/engines/eevee/shaders/lightprobe_filter_diffuse_frag.glsl
+++ b/source/blender/draw/engines/eevee/shaders/lightprobe_filter_diffuse_frag.glsl
@@ -1,4 +1,5 @@
 
+#pragma BLENDER_REQUIRE(random_lib.glsl)
 #pragma BLENDER_REQUIRE(bsdf_sampling_lib.glsl)
 #pragma BLENDER_REQUIRE(common_math_geom_lib.glsl)
 #pragma BLENDER_REQUIRE(irradiance_lib.glsl)
@@ -10,7 +11,6 @@ uniform float lodMax;
 uniform float intensityFac;
 
 uniform float sampleCount;
-uniform float invSampleCount;
 
 in vec3 worldPosition;
 
@@ -147,8 +147,10 @@ void main()
   float weight = 0.0;
   vec3 out_radiance = vec3(0.0);
   for (float i = 0; i < sampleCount; i++) {
+    vec3 Xi = rand2d_to_cylinder(hammersley_2d(i, sampleCount));
+
     float pdf;
-    vec3 L = sample_hemisphere(i, invSampleCount, N, T, B, pdf);
+    vec3 L = sample_uniform_hemisphere(Xi, N, T, B, pdf);
     float NL = dot(N, L);
 
     if (NL > 0.0) {
diff --git a/source/blender/draw/engines/eevee/shaders/lightprobe_filter_glossy_frag.glsl b/source/blender/draw/engines/eevee/shaders/lightprobe_filter_glossy_frag.glsl
index 99cbf2839ad..11fc1fb4295 100644
--- a/source/blender/draw/engines/eevee/shaders/lightprobe_filter_glossy_frag.glsl
+++ b/source/blender/draw/engines/eevee/shaders/lightprobe_filter_glossy_frag.glsl
@@ -1,4 +1,5 @@
 
+#pragma BLENDER_REQUIRE(random_lib.glsl)
 #pragma BLENDER_REQUIRE(bsdf_sampling_lib.glsl)
 #pragma BLENDER_REQUIRE(common_math_geom_lib.glsl)
 
@@ -12,7 +13,6 @@ uniform float intensityFac;
 uniform float fireflyFactor;
 
 uniform float sampleCount;
-uniform float invSampleCount;
 
 in vec3 worldPosition;
 
@@ -52,9 +52,11 @@ void main()
   float weight = 0.0;
   vec3 out_radiance = vec3(0.0);
   for (float i = 0; i < sampleCount; i++) {
+    vec3 Xi = rand2d_to_cylinder(hammersley_2d(i, sampleCount));
+
     float pdf;
     /* Microfacet normal */
-    vec3 H = sample_ggx(i, invSampleCount, roughness, V, N, T, B, pdf);
+    vec3 H = sample_ggx(Xi, roughness, V, N, T, B, pdf);
     vec3 L = -reflect(V, H);
     float NL = dot(N, L);
 
diff --git a/source/blender/draw/engines/eevee/shaders/lightprobe_filter_visibility_frag.glsl b/source/blender/draw/engines/eevee/shaders/lightprobe_filter_visibility_frag.glsl
index b802b39c56e..d25ef23a706 100644
--- a/source/blender/draw/engines/eevee/shaders/lightprobe_filter_visibility_frag.glsl
+++ b/source/blender/draw/engines/eevee/shaders/lightprobe_filter_visibility_frag.glsl
@@ -1,4 +1,5 @@
 
+#pragma BLENDER_REQUIRE(random_lib.glsl)
 #pragma BLENDER_REQUIRE(common_math_geom_lib.glsl)
 #pragma BLENDER_REQUIRE(bsdf_sampling_lib.glsl)
 #pragma BLENDER_REQUIRE(irradiance_lib.glsl)
@@ -14,7 +15,7 @@ uniform float visibilityRange;
 uniform float visibilityBlur;
 
 uniform float sampleCount;
-uniform float invSampleCount;
+uniform float;
 
 out vec4 FragColor;
 
@@ -80,13 +81,15 @@ void main()
   vec2 accum = vec2(0.0);
 
   for (float i = 0; i < sampleCount; i++) {
-    vec3 samp = sample_cone(i, invSampleCount, M_PI_2 * visibilityBlur, cos, T, B);
+    vec3 Xi = rand2d_to_cylinder(hammersley_2d(i, sampleCount));
+
+    vec3 samp = sample_uniform_cone(Xi, M_PI_2 * visibilityBlur, cos, T, B);
     float depth = texture(probeDepth, samp).r;
     depth = get_world_distance(depth, samp);
     accum += vec2(depth, depth * depth);
   }
 
-  accum *= invSampleCount;
+  accum /= sampleCount;
   accum = abs(accum);
 
   /* Encode to normalized RGBA 8 */
diff --git a/source/blender/draw/engines/eevee/shaders/random_lib.glsl b/source/blender/draw/engines/eevee/shaders/random_lib.glsl
new file mode 100644
index 00000000000..25a3e0f56b4
--- /dev/null
+++ b/source/blender/draw/engines/eevee/shaders/random_lib.glsl
@@ -0,0 +1,38 @@
+
+/**
+ * Random numbers and low discrepency sequences utilities.
+ **/
+
+#pragma BLENDER_REQUIRE(common_math_lib.glsl)
+
+/* From: http://holger.dammertz.org/stuff/notes_HammersleyOnHemisphere.html */
+float van_der_corput_radical_inverse(uint bits)
+{
+  bits = (bits << 16u) | (bits >> 16u);
+  bits = ((bits & 0x55555555u) << 1u) | ((bits & 0xAAAAAAAAu) >> 1u);
+  bits = ((bits & 0x33333333u) << 2u) | ((bits & 0xCCCCCCCCu) >> 2u);
+  bits = ((bits & 0x0F0F0F0Fu) << 4u) | ((bits & 0xF0F0F0F0u) >> 4u);
+  bits = ((bits & 0x00FF00FFu) << 8u) | ((bits & 0xFF00FF00u) >> 8u);
+  /* Same as dividing by 0x100000000. */
+  return float(bits) * 2.3283064365386963e-10;
+}
+
+vec2 hammersley_2d(float i, float sample_count)
+{
+  vec2 rand;
+  rand.x = i / sample_count;
+  rand.y = van_der_corput_radical_inverse(uint(i));
+  return rand;
+}
+
+/* This transform a 2d random sample (in [0..1] range) to a sample located on a cylinder of the
+ * same range. This is because the sampling functions expect such a random sample which is
+ * normally precomputed. */
+vec3 rand2d_to_cylinder(vec2 rand)
+{
+  float theta = rand.x;
+  float phi = (rand.y - 0.5) * M_2PI;
+  float cos_phi = cos(phi);
+  float sin_phi = sqrt(1.0 - sqr(cos_phi)) * sign(phi);
+  return vec3(theta, cos_phi, sin_phi);
+}