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

5 files changed, 29 insertions, 48 deletions

diff --git a/source/blender/draw/engines/workbench/shaders/workbench_data_lib.glsl b/source/blender/draw/engines/workbench/shaders/workbench_data_lib.glsl
index 069cb0f52d8..2ba6e0e8e55 100644
--- a/source/blender/draw/engines/workbench/shaders/workbench_data_lib.glsl
+++ b/source/blender/draw/engines/workbench/shaders/workbench_data_lib.glsl
@@ -4,12 +4,7 @@ struct LightData {
 };
 
 struct WorldData {
-	vec4 diffuse_light_x_pos;
-	vec4 diffuse_light_x_neg;
-	vec4 diffuse_light_y_pos;
-	vec4 diffuse_light_y_neg;
-	vec4 diffuse_light_z_pos;
-	vec4 diffuse_light_z_neg;
+	vec3 spherical_harmonics_coefs[9];
 	vec4 background_color_low;
 	vec4 background_color_high;
 	vec4 object_outline_color;
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. */
diff --git a/source/blender/draw/engines/workbench/workbench_data.c b/source/blender/draw/engines/workbench/workbench_data.c
index 45af9366a43..b4a2330f173 100644
--- a/source/blender/draw/engines/workbench/workbench_data.c
+++ b/source/blender/draw/engines/workbench/workbench_data.c
@@ -118,7 +118,6 @@ void workbench_private_data_init(WORKBENCH_PrivateData *wpd)
 			wpd->viewvecs[1][2] = vec_far[2] - wpd->viewvecs[0][2];
 		}
 	}
-
 }
 
 void workbench_private_data_get_light_direction(WORKBENCH_PrivateData *wpd, float light_direction[3])
@@ -154,20 +153,8 @@ void workbench_private_data_get_light_direction(WORKBENCH_PrivateData *wpd, floa
 		wd->num_lights = light_index;
 	}
 
-#if 0
-	if (STUDIOLIGHT_ORIENTATION_WORLD_ENABLED(wpd)) {
-		BKE_studiolight_ensure_flag(wpd->studio_light, STUDIOLIGHT_LIGHT_DIRECTION_CALCULATED);
-		float rot_matrix[3][3];
-		axis_angle_to_mat3_single(rot_matrix, 'Z', wpd->shading.studiolight_rot_z);
-		mul_v3_m3v3(e_data.display.light_direction, rot_matrix, wpd->studio_light->light_direction);
-	}
-	else {
-#else
-	{
-#endif
-		copy_v3_v3(light_direction, scene->display.light_direction);
-		negate_v3(light_direction);
-	}
+	copy_v3_v3(light_direction, scene->display.light_direction);
+	negate_v3(light_direction);
 
 	DRW_uniformbuffer_update(wpd->world_ubo, &wpd->world_data);
 }
diff --git a/source/blender/draw/engines/workbench/workbench_private.h b/source/blender/draw/engines/workbench/workbench_private.h
index 90d8cfc3dd2..9e43a5c4a48 100644
--- a/source/blender/draw/engines/workbench/workbench_private.h
+++ b/source/blender/draw/engines/workbench/workbench_private.h
@@ -112,12 +112,7 @@ typedef struct WORKBENCH_UBO_Light {
 } WORKBENCH_UBO_Light;
 
 typedef struct WORKBENCH_UBO_World {
-	float diffuse_light_x_pos[4];
-	float diffuse_light_x_neg[4];
-	float diffuse_light_y_pos[4];
-	float diffuse_light_y_neg[4];
-	float diffuse_light_z_pos[4];
-	float diffuse_light_z_neg[4];
+	float spherical_harmonics_coefs[9][4];
 	float background_color_low[4];
 	float background_color_high[4];
 	float object_outline_color[4];
diff --git a/source/blender/draw/engines/workbench/workbench_studiolight.c b/source/blender/draw/engines/workbench/workbench_studiolight.c
index 6451d1f57c8..e5e24cbb88a 100644
--- a/source/blender/draw/engines/workbench/workbench_studiolight.c
+++ b/source/blender/draw/engines/workbench/workbench_studiolight.c
@@ -34,14 +34,10 @@
 
 void studiolight_update_world(StudioLight *sl, WORKBENCH_UBO_World *wd)
 {
-	BKE_studiolight_ensure_flag(sl, STUDIOLIGHT_DIFFUSE_LIGHT_CALCULATED);
-
-	copy_v3_v3(wd->diffuse_light_x_pos, sl->diffuse_light[STUDIOLIGHT_X_POS]);
-	copy_v3_v3(wd->diffuse_light_x_neg, sl->diffuse_light[STUDIOLIGHT_X_NEG]);
-	copy_v3_v3(wd->diffuse_light_y_pos, sl->diffuse_light[STUDIOLIGHT_Y_POS]);
-	copy_v3_v3(wd->diffuse_light_y_neg, sl->diffuse_light[STUDIOLIGHT_Y_NEG]);
-	copy_v3_v3(wd->diffuse_light_z_pos, sl->diffuse_light[STUDIOLIGHT_Z_POS]);
-	copy_v3_v3(wd->diffuse_light_z_neg, sl->diffuse_light[STUDIOLIGHT_Z_NEG]);
+	BKE_studiolight_ensure_flag(sl, STUDIOLIGHT_SPHERICAL_HARMONICS_COEFFICIENTS_CALCULATED);
+	for (int i = 0; i < 9; i++) {
+		copy_v3_v3(wd->spherical_harmonics_coefs[i], sl->spherical_harmonics_coefs[i]);
+	}
 }
 
 static void compute_parallel_lines_nor_and_dist(const float v1[2], const float v2[2], const float v3[2], float r_line[2])