Eevee: Add Irradiance Grid support

Early implementation. Slow and still has quality
3 ways of storing irradiance:
- Spherical Harmonics: Have problem with directionnal lighting.
- HL2 diffuse cube: Very low resolution but smooth transitions.
- Diffuse cube: High storage requirement.

Also include some name change.

1 files changed, 19 insertions, 0 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 898c7bfc578..3997de7a22d 100644
--- a/source/blender/draw/engines/eevee/shaders/bsdf_sampling_lib.glsl
+++ b/source/blender/draw/engines/eevee/shaders/bsdf_sampling_lib.glsl
@@ -37,6 +37,11 @@ float pdf_ggx_reflect(float NH, float a2)
 	return NH * a2 / D_ggx_opti(NH, a2);
 }
 
+float pdf_hemisphere()
+{
+	return 0.5 * M_1_PI;
+}
+
 vec3 sample_ggx(float nsample, float a2, vec3 N, vec3 T, vec3 B)
 {
 	vec3 Xi = hammersley_3d(nsample);
@@ -52,3 +57,17 @@ vec3 sample_ggx(float nsample, float a2, vec3 N, vec3 T, vec3 B)
 
 	return tangent_to_world(Ht, N, T, B);
 }
+
+vec3 sample_hemisphere(float nsample, vec3 N, vec3 T, vec3 B)
+{
+	vec3 Xi = hammersley_3d(nsample);
+
+	float z = Xi.x; /* cos theta */
+	float r = sqrt( 1.0f - z*z ); /* sin theta */
+	float x = r * Xi.y;
+	float y = r * Xi.z;
+
+	vec3 Ht = vec3(x, y, z);
+
+	return tangent_to_world(Ht, N, T, B);
+}
\ No newline at end of file