Eevee: Diffuse Light (2/2) and GGX low quality lights

GGX is missing sun lamps area.

1 files changed, 91 insertions, 11 deletions

diff --git a/source/blender/draw/engines/eevee/shaders/bsdf_direct_lib.glsl b/source/blender/draw/engines/eevee/shaders/bsdf_direct_lib.glsl
index 4f66b79024d..953d4e0a551 100644
--- a/source/blender/draw/engines/eevee/shaders/bsdf_direct_lib.glsl
+++ b/source/blender/draw/engines/eevee/shaders/bsdf_direct_lib.glsl
@@ -2,6 +2,7 @@
 /* in other word, how materials react to scene lamps */
 
 /* Naming convention
+ * V       View vector (normalized)
  * N       World Normal (normalized)
  * L       Outgoing Light Vector (Surface to Light in World Space) (normalized)
  * Ldist   Distance from surface to the light
@@ -14,20 +15,69 @@ float direct_diffuse_point(vec3 N, vec3 L, float Ldist)
 {
 	float bsdf = max(0.0, dot(N, L));
 	bsdf /= Ldist * Ldist;
-	bsdf *= M_1_PI; /* Normalize */
+	bsdf *= M_PI / 2.0; /* Normalize */
 	return bsdf;
 }
-#if 0
-float direct_diffuse_sphere(vec3 N, vec3 L)
+
+/* From Frostbite PBR Course
+ * Analitical irradiance from a sphere with correct horizon handling
+ * http://www.frostbite.com/wp-content/uploads/2014/11/course_notes_moving_frostbite_to_pbr.pdf */
+float direct_diffuse_sphere(vec3 N, vec3 L, float Ldist, float radius)
 {
+	radius = max(radius, 0.0001);
+	float costheta = clamp(dot(N, L), -0.999, 0.999);
+	float h = min(radius / Ldist , 0.9999);
+	float h2 = h*h;
+	float costheta2 = costheta * costheta;
+	float bsdf;
+
+	if (costheta2 > h2) {
+		bsdf = M_PI * h2 * clamp(costheta, 0.0, 1.0);
+	}
+	else {
+		float sintheta = sqrt(1.0 - costheta2);
+		float x = sqrt(1.0 / h2 - 1.0);
+		float y = -x * (costheta / sintheta);
+		float sinthetasqrty = sintheta * sqrt(1.0 - y * y);
+		bsdf = (costheta * acos(y) - x * sinthetasqrty) * h2 + atan(sinthetasqrty / x);
+	}
+
+	/* Energy conservation + cycle matching */
+	bsdf = max(bsdf, 0.0);
+	bsdf *= M_1_PI;
+	bsdf *= sphere_energy(radius);
 
+	return bsdf;
 }
 
-float direct_diffuse_rectangle(vec3 N, vec3 L)
+/* From Frostbite PBR Course
+ * http://www.frostbite.com/wp-content/uploads/2014/11/course_notes_moving_frostbite_to_pbr.pdf */
+float direct_diffuse_rectangle(
+        vec3 W, vec3 N, vec3 L,
+        float Ldist, vec3 Lx, vec3 Ly, vec3 Lz, float Lsizex, float Lsizey)
 {
+	vec3 lco = L * Ldist;
+
+	/* Surface to corner vectors */
+	vec3 p0 = lco + Lx * -Lsizex + Ly *  Lsizey;
+	vec3 p1 = lco + Lx * -Lsizex + Ly * -Lsizey;
+	vec3 p2 = lco + Lx *  Lsizex + Ly * -Lsizey;
+	vec3 p3 = lco + Lx *  Lsizex + Ly *  Lsizey;
+
+	float solidAngle = rectangle_solid_angle(p0, p1, p2, p3);
 
+	float bsdf = solidAngle * 0.2 * (
+		max(0.0, dot(normalize(p0), N)) +
+		max(0.0, dot(normalize(p1), N)) +
+		max(0.0, dot(normalize(p2), N)) +
+		max(0.0, dot(normalize(p3), N)) +
+		max(0.0, dot(L, N))
+	);
+
+	bsdf *= rectangle_energy(Lsizex * 2.0, Lsizey * 2.0);
+
+	return bsdf;
 }
-#endif
 
 /* infinitly far away point source, no decay */
 float direct_diffuse_sun(vec3 N, vec3 L)
@@ -42,25 +92,55 @@ float direct_diffuse_unit_disc(vec3 N, vec3 L)
 {
 
 }
+#endif
 
 /* ----------- GGx ------------ */
-float direct_ggx_point(vec3 N, vec3 L)
+float direct_ggx_point(vec3 N, vec3 L, vec3 V, float roughness)
 {
-	float bsdf = max(0.0, dot(N, L));
-	bsdf *= M_1_PI; /* Normalize */
-	return bsdf;
+	return bsdf_ggx(N, L, V, roughness);
 }
 
-float direct_ggx_sphere(vec3 N, vec3 L)
+float direct_ggx_sphere(vec3 N, vec3 L, vec3 V, float Ldist, float radius, float roughness)
 {
+	vec3 R = reflect(V, N);
+
+	float energy_conservation = 1.0;
+	mrp_sphere(radius, Ldist, R, L, roughness, energy_conservation);
+	float bsdf = bsdf_ggx(N, L, V, roughness);
 
+	bsdf *= energy_conservation / (Ldist * Ldist);
+	bsdf *= sphere_energy(radius) * max(radius * radius, 1e-16); /* radius is already inside energy_conservation */
+	bsdf *= M_PI;
+
+	return bsdf;
 }
 
-float direct_ggx_rectangle(vec3 N, vec3 L)
+float direct_ggx_rectangle(
+        vec3 W, vec3 N, vec3 L, vec3 V,
+        float Ldist, vec3 Lx, vec3 Ly, vec3 Lz, float Lsizex, float Lsizey, float roughness)
 {
+	vec3 lco = L * Ldist;
+
+	/* Surface to corner vectors */
+	vec3 p0 = lco + Lx * -Lsizex + Ly *  Lsizey;
+	vec3 p1 = lco + Lx * -Lsizex + Ly * -Lsizey;
+	vec3 p2 = lco + Lx *  Lsizex + Ly * -Lsizey;
+	vec3 p3 = lco + Lx *  Lsizex + Ly *  Lsizey;
 
+	float solidAngle = rectangle_solid_angle(p0, p1, p2, p3);
+
+	vec3 R = reflect(V, N);
+	mrp_area(R, N, W, W + lco, Lx, Ly, Lz, Lsizex, Lsizey, Ldist, L);
+
+	float bsdf = bsdf_ggx(N, L, V, roughness) * solidAngle;
+
+	bsdf *= pow(max(0.0, dot(R, Lz)), 0.5); /* fade mrp artifacts */
+	bsdf *= rectangle_energy(Lsizex * 2.0, Lsizey * 2.0);
+
+	return bsdf;
 }
 
+#if 0
 float direct_ggx_disc(vec3 N, vec3 L)
 {