Eevee: Move cube shadows to octahedron shadowmaps.

We render linear distance to the light in a R32 texture and store it into an octahedron projection inside a 2D texture array.

This render the sampling function much more simpler and without edge artifacts.

7 files changed, 117 insertions, 67 deletions

diff --git a/source/blender/draw/engines/eevee/shaders/lit_surface_frag.glsl b/source/blender/draw/engines/eevee/shaders/lit_surface_frag.glsl
index 1e29aed739d..1c124c06744 100644
--- a/source/blender/draw/engines/eevee/shaders/lit_surface_frag.glsl
+++ b/source/blender/draw/engines/eevee/shaders/lit_surface_frag.glsl
@@ -11,8 +11,7 @@ uniform vec3 shCoefs[9];
 #ifndef USE_LTC
 uniform sampler2D brdfLut;
 #endif
-uniform sampler2DArrayShadow shadowCubes;
-uniform sampler2DArrayShadow shadowMaps;
+uniform sampler2DArray shadowCubes;
 uniform sampler2DArrayShadow shadowCascades;
 
 layout(std140) uniform light_block {
@@ -130,75 +129,30 @@ float light_visibility(LightData ld, ShadingData sd)
 
 		vis *= texture(shadowCascades, vec4(shpos.xy, shid * float(MAX_CASCADE_NUM) + cascade, shpos.z));
 	}
-	else if (ld.l_shadowid >= MAX_SHADOW_CUBE) {
-		/* Shadow Map */
-		float shid = ld.l_shadowid - MAX_SHADOW_CUBE;
-		ShadowMapData smd = shadows_map_data[int(shid)];
-		vec4 shpos = smd.shadowmat * vec4(sd.W, 1.0);
-		shpos.z -= smd.sh_map_bias * shpos.w;
-		shpos.xyz /= shpos.w;
-
-		if (shpos.w > 0.0 && min(shpos.x, shpos.y) > 0.0 && max(shpos.x, shpos.y) < 1.0) {
-			vis *= texture(shadowMaps, vec4(shpos.xy, shid, shpos.z));
-		}
-	}
 	else {
 		/* Shadow Cube */
 		float shid = ld.l_shadowid;
 		ShadowCubeData scd = shadows_cube_data[int(shid)];
 
-		float face;
-		vec2 uvs;
-		vec3 Linv = sd.L;
-		vec3 Labs = abs(Linv);
-		vec3 maj_axis;
-
-		if (max(Labs.y, Labs.z) < Labs.x) {
-			if (Linv.x > 0.0) {
-				face = 1.0;
-				uvs = vec2(1.0, -1.0) * Linv.zy / -Linv.x;
-				maj_axis = vec3(1.0, 0.0, 0.0);
-			}
-			else {
-				face = 0.0;
-				uvs = -Linv.zy / Linv.x;
-				maj_axis = vec3(-1.0, 0.0, 0.0);
-			}
-		}
-		else if (max(Labs.x, Labs.z) < Labs.y) {
-			if (Linv.y > 0.0) {
-				face = 2.0;
-				uvs = vec2(-1.0, 1.0) * Linv.xz / Linv.y;
-				maj_axis = vec3(0.0, 1.0, 0.0);
-			}
-			else {
-				face = 3.0;
-				uvs = -Linv.xz / -Linv.y;
-				maj_axis = vec3(0.0, -1.0, 0.0);
-			}
-		}
-		else {
-			if (Linv.z > 0.0) {
-				face = 5.0;
-				uvs = Linv.xy / Linv.z;
-				maj_axis = vec3(0.0, 0.0, 1.0);
-			}
-			else {
-				face = 4.0;
-				uvs = vec2(-1.0, 1.0) * Linv.xy / -Linv.z;
-				maj_axis = vec3(0.0, 0.0, -1.0);
-			}
+		vec3 cubevec = sd.W - ld.l_position;
+		float dist = length(cubevec);
+
+		/* projection onto octahedron */
+		cubevec /= dot( vec3(1), abs(cubevec) );
+
+		/* out-folding of the downward faces */
+		if ( cubevec.z < 0.0 ) {
+			cubevec.xy = (1.0 - abs(cubevec.yx)) * sign(cubevec.xy);
 		}
+		vec2 texelSize = vec2(1.0 / 512.0);
 
-		uvs = uvs * 0.5 + 0.5;
+		/* mapping to [0;1]ˆ2 texture space */
+		vec2 uvs = cubevec.xy * (0.5) + 0.5;
+		uvs = uvs * (1.0 - 2.0 * texelSize) + 1.0 * texelSize; /* edge filtering fix */
 
-		/* Depth in lightspace to compare against shadow map */
-		float w = dot(maj_axis, sd.l_vector);
-		w -= scd.sh_map_bias * w;
-		bool is_persp = (ProjectionMatrix[3][3] == 0.0);
-		float shdepth = buffer_depth(is_persp, w, scd.sh_cube_far, scd.sh_cube_near);
+		float sh_test = step(0, texture(shadowCubes, vec3(uvs, shid)).r - dist);
 
-		vis *= texture(shadowCubes, vec4(uvs, shid * 6.0 + face, shdepth));
+		vis *= sh_test;
 	}
 
 	return vis;
diff --git a/source/blender/draw/engines/eevee/shaders/shadow_frag.glsl b/source/blender/draw/engines/eevee/shaders/shadow_frag.glsl
index 29335207851..0b7356d812b 100644
--- a/source/blender/draw/engines/eevee/shaders/shadow_frag.glsl
+++ b/source/blender/draw/engines/eevee/shaders/shadow_frag.glsl
@@ -1,3 +1,8 @@
 
+in float linearDistance;
+
+out vec4 FragColor;
+
 void main() {
+	FragColor = vec4(linearDistance, 0.0, 0.0, 1.0);
 }
diff --git a/source/blender/draw/engines/eevee/shaders/shadow_geom.glsl b/source/blender/draw/engines/eevee/shaders/shadow_geom.glsl
index bac6a10eee1..c4738de2f31 100644
--- a/source/blender/draw/engines/eevee/shaders/shadow_geom.glsl
+++ b/source/blender/draw/engines/eevee/shaders/shadow_geom.glsl
@@ -1,21 +1,26 @@
 
-layout(triangles) in;
-layout(triangle_strip, max_vertices=3) out;
-
 layout(std140) uniform shadow_render_block {
 	mat4 ShadowMatrix[6];
-	int Layer;
+	vec4 lampPosition;
+	int layer;
 };
 
+layout(triangles) in;
+layout(triangle_strip, max_vertices=3) out;
+
 in vec4 vPos[];
+in float lDist[];
 flat in int face[];
 
+out float linearDistance;
+
 void main() {
 	int f = face[0];
-	gl_Layer = Layer + f;
+	gl_Layer = f;
 
 	for (int v = 0; v < 3; ++v) {
 		gl_Position = ShadowMatrix[f] * vPos[v];
+		linearDistance = lDist[v];
 		EmitVertex();
 	}
 
diff --git a/source/blender/draw/engines/eevee/shaders/shadow_store_frag.glsl b/source/blender/draw/engines/eevee/shaders/shadow_store_frag.glsl
new file mode 100644
index 00000000000..08453080ed2
--- /dev/null
+++ b/source/blender/draw/engines/eevee/shaders/shadow_store_frag.glsl
@@ -0,0 +1,47 @@
+
+uniform samplerCube shadowCube;
+
+out vec4 FragColor;
+
+vec3 octahedral_to_cubemap_proj(vec2 co)
+{
+	co = co * 2.0 - 1.0;
+
+	vec2 abs_co = abs(co);
+	vec3 v = vec3(co, 1.0 - (abs_co.x + abs_co.y));
+
+	if ( abs_co.x + abs_co.y > 1.0 ) {
+		v.xy = (abs(co.yx) - 1.0) * -sign(co.xy);
+	}
+
+	return v;
+}
+
+void main() {
+	const vec2 texelSize = vec2(1.0 / 512.0);
+
+	vec2 uvs = gl_FragCoord.xy * texelSize;
+
+	/* add a 2 pixel border to ensure filtering is correct */
+	uvs.xy *= 1.0 + texelSize * 2.0;
+	uvs.xy -= texelSize;
+
+	float pattern = 1.0;
+
+	/* edge mirroring : only mirror if directly adjacent
+	 * (not diagonally adjacent) */
+	vec2 m = abs(uvs - 0.5) + 0.5;
+	vec2 f = floor(m);
+	if (f.x - f.y != 0.0) {
+		uvs.xy = 1.0 - uvs.xy;
+	}
+
+	/* clamp to [0-1] */
+	uvs.xy = fract(uvs.xy);
+
+	/* get cubemap vector */
+	vec3 cubevec = octahedral_to_cubemap_proj(uvs.xy);
+
+	/* get cubemap vector */
+	FragColor = texture(shadowCube, cubevec).rrrr;
+}
\ No newline at end of file
diff --git a/source/blender/draw/engines/eevee/shaders/shadow_store_geom.glsl b/source/blender/draw/engines/eevee/shaders/shadow_store_geom.glsl
new file mode 100644
index 00000000000..f14354ad4cd
--- /dev/null
+++ b/source/blender/draw/engines/eevee/shaders/shadow_store_geom.glsl
@@ -0,0 +1,22 @@
+
+layout(std140) uniform shadow_render_block {
+	mat4 ShadowMatrix[6];
+	vec4 lampPosition;
+	int layer;
+};
+
+layout(triangles) in;
+layout(triangle_strip, max_vertices=3) out;
+
+in vec4 vPos[];
+
+void main() {
+	gl_Layer = layer;
+
+	for (int v = 0; v < 3; ++v) {
+		gl_Position = vPos[v];
+		EmitVertex();
+	}
+
+	EndPrimitive();
+}
\ No newline at end of file
diff --git a/source/blender/draw/engines/eevee/shaders/shadow_store_vert.glsl b/source/blender/draw/engines/eevee/shaders/shadow_store_vert.glsl
new file mode 100644
index 00000000000..dee020f19b4
--- /dev/null
+++ b/source/blender/draw/engines/eevee/shaders/shadow_store_vert.glsl
@@ -0,0 +1,8 @@
+
+in vec3 pos;
+
+out vec4 vPos;
+
+void main() {
+	vPos = vec4(pos, 1.0);
+}
\ No newline at end of file
diff --git a/source/blender/draw/engines/eevee/shaders/shadow_vert.glsl b/source/blender/draw/engines/eevee/shaders/shadow_vert.glsl
index ffb99f1b35c..323cf4d2a99 100644
--- a/source/blender/draw/engines/eevee/shaders/shadow_vert.glsl
+++ b/source/blender/draw/engines/eevee/shaders/shadow_vert.glsl
@@ -1,12 +1,21 @@
 
+layout(std140) uniform shadow_render_block {
+	mat4 ShadowMatrix[6];
+	vec4 lampPosition;
+	int layer;
+};
+
 uniform mat4 ShadowModelMatrix;
 
 in vec3 pos;
 
 out vec4 vPos;
+out float lDist;
+
 flat out int face;
 
 void main() {
 	vPos = ShadowModelMatrix * vec4(pos, 1.0);
+	lDist = distance(lampPosition.xyz, vPos.xyz);
 	face = gl_InstanceID;
 }
\ No newline at end of file