Eevee: Polishing of Exponential Shadow mapping

Added exponent parameter to tweak light bleeding.
Added depth bias to the shadow test.
Added better blurring using 32 samples.

source/blender/blenkernel/intern/lamp.c

@@ -69,6 +69,7 @@ void BKE_lamp_init(Lamp *la)
 	la->bufsize = 512;
 	la->clipsta = 0.5f;
 	la->clipend = 40.0f;
+	la->bleedexp = 120.0f;
 	la->samp = 3;
 	la->bias = 1.0f;
 	la->soft = 3.0f;

source/blender/blenloader/intern/versioning_280.c

@@ -31,6 +31,7 @@
 #include "DNA_object_types.h"
 #include "DNA_camera_types.h"
 #include "DNA_gpu_types.h"
+#include "DNA_lamp_types.h"
 #include "DNA_layer_types.h"
 #include "DNA_material_types.h"
 #include "DNA_mesh_types.h"
@@ -351,6 +352,12 @@ void blo_do_versions_280(FileData *fd, Library *UNUSED(lib), Main *main)
 	}
 
 	if (!MAIN_VERSION_ATLEAST(main, 280, 1)) {
+		if (!DNA_struct_elem_find(fd->filesdna, "Lamp", "float", "bleedexp"))	{
+			for (Lamp *la = main->lamp.first; la; la = la->id.next) {
+				la->bleedexp = 120.0f;
+			}
+		}
+
 		if (!DNA_struct_elem_find(fd->filesdna, "GPUDOFSettings", "float", "ratio"))	{
 			for (Camera *ca = main->camera.first; ca; ca = ca->id.next) {
 				ca->gpu_dof.ratio = 1.0f;

source/blender/draw/engines/eevee/eevee_lights.c

@@ -382,6 +382,7 @@ static void eevee_shadow_cube_setup(Object *ob, EEVEE_LampsInfo *linfo, EEVEE_La
 	evsh->bias = 0.05f * la->bias;
 	evsh->near = la->clipsta;
 	evsh->far = la->clipend;
+	evsh->exp = la->bleedexp;
 
 	evli->shadowid = (float)(evsmp->shadow_id);
 }
@@ -732,12 +733,14 @@ void EEVEE_draw_shadows(EEVEE_SceneLayerData *sldata, EEVEE_PassList *psl)
 	/* Render each shadow to one layer of the array */
 	for (i = 0; (ob = linfo->shadow_cube_ref[i]) && (i < MAX_SHADOW_CUBE); i++) {
 		EEVEE_LampEngineData *led = eevee_get_lamp_engine_data(ob);
+		Lamp *la = (Lamp *)ob->data;
 
 		if (led->need_update) {
 			EEVEE_ShadowCubeData *evscd = (EEVEE_ShadowCubeData *)led->storage;
 			EEVEE_ShadowRender *srd = &linfo->shadow_render_data;
 
 			srd->layer = i;
+			srd->exponent = la->bleedexp;
 			copy_v3_v3(srd->position, ob->obmat[3]);
 			for (int j = 0; j < 6; ++j) {
 				copy_m4_m4(srd->shadowmat[j], evscd->viewprojmat[j]);

source/blender/draw/engines/eevee/eevee_private.h

@@ -114,7 +114,7 @@ typedef struct EEVEE_Light {
 } EEVEE_Light;
 
 typedef struct EEVEE_ShadowCube {
-	float near, far, bias, pad;
+	float near, far, bias, exp;
 } EEVEE_ShadowCube;
 
 typedef struct EEVEE_ShadowMap {
@@ -133,6 +133,7 @@ typedef struct EEVEE_ShadowRender {
 	float position[3];
 	float pad;
 	int layer;
+	float exponent;
 } EEVEE_ShadowRender;
 
 /* ************ LIGHT DATA ************* */

source/blender/draw/engines/eevee/shaders/bsdf_common_lib.glsl

@@ -36,13 +36,14 @@ struct LightData {
 
 
 struct ShadowCubeData {
-	vec4 near_far_bias;
+	vec4 near_far_bias_exp;
 };
 
 /* convenience aliases */
-#define sh_cube_near   near_far_bias.x
-#define sh_cube_far    near_far_bias.y
-#define sh_cube_bias   near_far_bias.z
+#define sh_cube_near   near_far_bias_exp.x
+#define sh_cube_far    near_far_bias_exp.y
+#define sh_cube_bias   near_far_bias_exp.z
+#define sh_cube_exp    near_far_bias_exp.w
 
 
 struct ShadowMapData {

source/blender/draw/engines/eevee/shaders/lit_surface_frag.glsl

@@ -176,11 +176,11 @@ void light_visibility(LightData ld, ShadingData sd, out float vis)
 		ShadowCubeData scd = shadows_cube_data[int(shid)];
 
 		vec3 cubevec = sd.W - ld.l_position;
-		float dist = length(cubevec);
+		float dist = length(cubevec) - scd.sh_cube_bias;
 
 		float z = texture_octahedron(shadowCubes, vec4(cubevec, shid)).r;
 
-		float esm_test = min(1.0, exp(-5.0 * dist) * z);
+		float esm_test = saturate(exp(scd.sh_cube_exp * (z - dist)));
 		float sh_test = step(0, z - dist);
 
 		vis *= esm_test;

source/blender/draw/engines/eevee/shaders/shadow_frag.glsl

@@ -3,6 +3,7 @@ layout(std140) uniform shadow_render_block {
 	mat4 ShadowMatrix[6];
 	vec4 lampPosition;
 	int layer;
+	float exponent;
 };
 
 in vec3 worldPosition;
@@ -11,5 +12,5 @@ out vec4 FragColor;
 
 void main() {
 	float dist = distance(lampPosition.xyz, worldPosition.xyz);
-	FragColor = vec4(exp(5.0 * dist), 0.0, 0.0, 1.0);
+	FragColor = vec4(dist, 0.0, 0.0, 1.0);
 }

source/blender/draw/engines/eevee/shaders/shadow_geom.glsl

@@ -3,6 +3,7 @@ layout(std140) uniform shadow_render_block {
 	mat4 ShadowMatrix[6];
 	vec4 lampPosition;
 	int layer;
+	float exponent;
 };
 
 layout(triangles) in;

source/blender/draw/engines/eevee/shaders/shadow_store_frag.glsl

@@ -1,4 +1,11 @@
 
+layout(std140) uniform shadow_render_block {
+	mat4 ShadowMatrix[6];
+	vec4 lampPosition;
+	int layer;
+	float exponent;
+};
+
 uniform samplerCube shadowCube;
 
 out vec4 FragColor;
@@ -24,6 +31,35 @@ void make_orthonormal_basis(vec3 N, out vec3 T, out vec3 B)
 	B = cross(N, T);
 }
 
+#define NUM_SAMPLE 32
+vec2 poisson_disc[32] = vec2[32](
+	vec2( 0.476,  0.854), vec2(-0.659, -0.670),
+	vec2( 0.905, -0.270), vec2( 0.215, -0.133),
+	vec2(-0.595,  0.242), vec2(-0.146,  0.519),
+	vec2( 0.108, -0.930), vec2( 0.807,  0.449),
+
+	vec2(-0.476, -0.854), vec2( 0.659,  0.670),
+	vec2(-0.905,  0.270), vec2(-0.215,  0.133),
+	vec2( 0.595, -0.242), vec2( 0.146, -0.519),
+	vec2(-0.108,  0.930), vec2(-0.807, -0.449),
+
+	vec2(-0.854,  0.476), vec2( 0.670, -0.659),
+	vec2( 0.270,  0.905), vec2( 0.133,  0.215),
+	vec2(-0.242, -0.595), vec2(-0.519, -0.146),
+	vec2( 0.930,  0.108), vec2(-0.449,  0.807),
+
+	vec2( 0.854, -0.476), vec2(-0.670,  0.659),
+	vec2(-0.270, -0.905), vec2(-0.133, -0.215),
+	vec2( 0.242,  0.595), vec2( 0.519,  0.146),
+	vec2(-0.930, -0.108), vec2( 0.449, -0.807)
+);
+
+/* Marco Salvi's GDC 2008 presentation about shadow maps pre-filtering techniques slide 24 */
+float ln_space_prefilter(float w0, float x, float w1, float y)
+{
+    return x + log(w0 + w1 * exp(y - x));
+}
+
 void main() {
 	const vec2 texelSize = vec2(1.0 / 512.0);
 
@@ -52,13 +88,25 @@ void main() {
 	vec3 T, B;
 	make_orthonormal_basis(cubevec, T, B);
 
-	vec2 offsetvec = texelSize.xy * vec2(-1.0, 1.0); /* Totally arbitrary */
-
 	/* get cubemap shadow value */
-	FragColor  = texture(shadowCube, cubevec + offsetvec.x * T + offsetvec.x * B).rrrr;
-	FragColor += texture(shadowCube, cubevec + offsetvec.x * T + offsetvec.y * B).rrrr;
-	FragColor += texture(shadowCube, cubevec + offsetvec.y * T + offsetvec.x * B).rrrr;
-	FragColor += texture(shadowCube, cubevec + offsetvec.y * T + offsetvec.y * B).rrrr;
+	const float blur_radius = 5.0 / 512.0; /* Totally arbitrary */
+	const float weight = 1.0 / float(NUM_SAMPLE);
+	float accum = 0.0;
 
-	FragColor /= 4.0;
+	/* Poisson disc blur in log space. */
+	vec2 offsetvec = poisson_disc[0].xy * blur_radius;
+	float depth1 = texture(shadowCube, cubevec + offsetvec.x * T + offsetvec.y * B).r;
+
+	offsetvec = poisson_disc[1].xy * blur_radius;
+	float depth2 = texture(shadowCube, cubevec + offsetvec.x * T + offsetvec.y * B).r;
+
+	accum = ln_space_prefilter(weight, depth1, weight, depth2);
+
+	for (int i = 2; i < NUM_SAMPLE; ++i) {
+		vec2 offsetvec = poisson_disc[i].xy * blur_radius;
+		depth1 = texture(shadowCube, cubevec + offsetvec.x * T + offsetvec.y * B).r;
+		accum = ln_space_prefilter(1.0, accum, weight, depth1);
+	}
+
+	FragColor = vec4(accum, accum, accum, 1.0);
 }

source/blender/draw/engines/eevee/shaders/shadow_store_geom.glsl

@@ -3,6 +3,7 @@ layout(std140) uniform shadow_render_block {
 	mat4 ShadowMatrix[6];
 	vec4 lampPosition;
 	int layer;
+	float exponent;
 };
 
 layout(triangles) in;

source/blender/makesdna/DNA_lamp_types.h

@@ -67,7 +67,7 @@ typedef struct Lamp {
 	short pad2;
 	
 	float clipsta, clipend;
-	float bias, soft, compressthresh, bleedbias, pad5;
+	float bias, soft, compressthresh, bleedbias, bleedexp;
 	short bufsize, samp, buffers, filtertype;
 	char bufflag, buftype;
 	

source/blender/makesrna/intern/rna_lamp.c

@@ -596,6 +596,12 @@ static void rna_def_lamp_shadow(StructRNA *srna, int spot, int area)
 	RNA_def_property_ui_text(prop, "Shadow Buffer Bleed Bias", "Bias for reducing light-bleed on variance shadow maps");
 	RNA_def_property_update(prop, 0, "rna_Lamp_update");
 
+	prop = RNA_def_property(srna, "shadow_buffer_exp", PROP_FLOAT, PROP_NONE);
+	RNA_def_property_float_sdna(prop, NULL, "bleedexp");
+	RNA_def_property_range(prop, 1.0f, 9999.0f);
+	RNA_def_property_ui_text(prop, "Shadow Buffer Exponent", "Bias for reducing light-bleed on exponential shadow maps");
+	RNA_def_property_update(prop, 0, "rna_Lamp_update");
+
 	prop = RNA_def_property(srna, "shadow_buffer_soft", PROP_FLOAT, PROP_NONE);
 	RNA_def_property_float_sdna(prop, NULL, "soft");
 	RNA_def_property_range(prop, 0.0f, 100.0f);