Workbench: increased Quality of the diffuse lighting model

- implemented Spherical Harmonics L2 for diffuse shading.

TODO: caching the precalculated harmonics so it won't take soo long to
open the popover

1 files changed, 21 insertions, 13 deletions

diff --git a/source/blender/draw/engines/workbench/shaders/workbench_world_light_lib.glsl b/source/blender/draw/engines/workbench/shaders/workbench_world_light_lib.glsl
index 9d256e5350a..71adc751f0a 100644
--- a/source/blender/draw/engines/workbench/shaders/workbench_world_light_lib.glsl
+++ b/source/blender/draw/engines/workbench/shaders/workbench_world_light_lib.glsl
@@ -1,24 +1,32 @@
 #define BLINN
 
+vec3 spherical_harmonics_L2(vec3 N, vec3 spherical_harmonics_coefs[9])
+{
+	vec3 sh = vec3(0.0);
+
+	sh += 0.282095 * spherical_harmonics_coefs[0];
+
+	sh += -0.488603 * N.z * spherical_harmonics_coefs[1];
+	sh += 0.488603 * N.y * spherical_harmonics_coefs[2];
+	sh += -0.488603 * N.x * spherical_harmonics_coefs[3];
+
+	sh += 1.092548 * N.x * N.z * spherical_harmonics_coefs[4];
+	sh += -1.092548 * N.z * N.y * spherical_harmonics_coefs[5];
+	sh += 0.315392 * (3.0 * N.y * N.y - 1.0) * spherical_harmonics_coefs[6];
+	sh += -1.092548 * N.x * N.y * spherical_harmonics_coefs[7];
+	sh += 0.546274 * (N.x * N.x - N.z * N.z) * spherical_harmonics_coefs[8];
+
+	return sh;
+}
+
 vec3 get_world_diffuse_light(WorldData world_data, vec3 N)
 {
-	vec4 result = world_data.diffuse_light_x_pos * clamp(N.x, 0.0, 1.0);
-	result = mix(result, world_data.diffuse_light_x_neg, clamp(-N.x, 0.0, 1.0));
-	result = mix(result, world_data.diffuse_light_y_pos, clamp(-N.y, 0.0, 1.0));
-	result = mix(result, world_data.diffuse_light_y_neg, clamp(N.y, 0.0, 1.0));
-	result = mix(result, world_data.diffuse_light_z_pos, clamp(N.z, 0.0, 1.0));
-	return mix(result, world_data.diffuse_light_z_neg, clamp(-N.z, 0.0, 1.0)).xyz;
+	return (spherical_harmonics_L2(vec3(N.x, N.y, -N.z), world_data.spherical_harmonics_coefs));
 }
 
 vec3 get_camera_diffuse_light(WorldData world_data, vec3 N)
 {
-	vec4 result = world_data.diffuse_light_x_pos * clamp(N.x, 0.0, 1.0);
-	result = mix(result, world_data.diffuse_light_x_neg, clamp(-N.x, 0.0, 1.0));
-	result = mix(result, world_data.diffuse_light_z_pos, clamp( N.y, 0.0, 1.0));
-	result = mix(result, world_data.diffuse_light_z_neg, clamp(-N.y, 0.0, 1.0));
-	result = mix(result, world_data.diffuse_light_y_pos, clamp( N.z, 0.0, 1.0));
-	result = mix(result, world_data.diffuse_light_y_neg, clamp(-N.z, 0.0, 1.0));
-	return result.rgb;
+	return (spherical_harmonics_L2(vec3(N.x, -N.z, -N.y), world_data.spherical_harmonics_coefs));
 }
 
 /* N And I are in View Space. */