Eevee: Refraction: Add "thickness" parameter.

This enables to fake a second refraction event. This is great to simulate thin planar objects such as glass panels.

2 files changed, 52 insertions, 33 deletions

diff --git a/source/blender/draw/engines/eevee/eevee_materials.c b/source/blender/draw/engines/eevee/eevee_materials.c
index cf27cba0b1a..517d7780719 100644
--- a/source/blender/draw/engines/eevee/eevee_materials.c
+++ b/source/blender/draw/engines/eevee/eevee_materials.c
@@ -353,7 +353,7 @@ static char *eevee_get_volume_defines(int options)
  **/
 static void add_standard_uniforms(
         DRWShadingGroup *shgrp, EEVEE_SceneLayerData *sldata, EEVEE_Data *vedata,
-        int *ssr_id, float *refract_thickness)
+        int *ssr_id, float *refract_depth, bool use_ssrefraction)
 {
 	if (ssr_id == NULL) {
 		static int no_ssr = -1.0f;
@@ -379,13 +379,15 @@ static void add_standard_uniforms(
 	DRW_shgroup_uniform_buffer(shgrp, "shadowCubes", &sldata->shadow_depth_cube_pool);
 	DRW_shgroup_uniform_buffer(shgrp, "shadowCascades", &sldata->shadow_depth_cascade_pool);
 	DRW_shgroup_uniform_int(shgrp, "outputSsrId", ssr_id, 1);
-	if (vedata->stl->effects->use_ao || refract_thickness) {
+	if (refract_depth != NULL) {
+		DRW_shgroup_uniform_float(shgrp, "refractionDepth", refract_depth, 1);
+	}
+	if (vedata->stl->effects->use_ao || use_ssrefraction) {
 		DRW_shgroup_uniform_vec4(shgrp, "viewvecs[0]", (float *)vedata->stl->g_data->viewvecs, 2);
 		DRW_shgroup_uniform_buffer(shgrp, "maxzBuffer", &vedata->txl->maxzbuffer);
 	}
-	if (refract_thickness) {
+	if (use_ssrefraction) {
 		DRW_shgroup_uniform_buffer(shgrp, "colorBuffer", &vedata->txl->refract_color);
-		DRW_shgroup_uniform_float(shgrp, "refractionThickness", refract_thickness, 1);
 		DRW_shgroup_uniform_vec4(shgrp, "ssrParameters", &vedata->stl->effects->ssr_quality, 1);
 		DRW_shgroup_uniform_float(shgrp, "borderFadeFactor", &vedata->stl->effects->ssr_border_fac, 1);
 		DRW_shgroup_uniform_float(shgrp, "maxRoughness", &vedata->stl->effects->ssr_max_roughness, 1);
@@ -733,7 +735,7 @@ static struct DRWShadingGroup *EEVEE_default_shading_group_create(
 	}
 
 	DRWShadingGroup *shgrp = DRW_shgroup_create(e_data.default_lit[options], pass);
-	add_standard_uniforms(shgrp, sldata, vedata, &ssr_id, NULL);
+	add_standard_uniforms(shgrp, sldata, vedata, &ssr_id, NULL, false);
 
 	return shgrp;
 }
@@ -763,7 +765,7 @@ static struct DRWShadingGroup *EEVEE_default_shading_group_get(
 		vedata->psl->default_pass[options] = DRW_pass_create("Default Lit Pass", state);
 
 		DRWShadingGroup *shgrp = DRW_shgroup_create(e_data.default_lit[options], vedata->psl->default_pass[options]);
-		add_standard_uniforms(shgrp, sldata, vedata, &ssr_id, NULL);
+		add_standard_uniforms(shgrp, sldata, vedata, &ssr_id, NULL, false);
 	}
 
 	return DRW_shgroup_create(e_data.default_lit[options], vedata->psl->default_pass[options]);
@@ -944,10 +946,10 @@ static void material_opaque(
 
 		*shgrp = DRW_shgroup_material_create(*gpumat, use_refract ? psl->refract_pass : psl->material_pass);
 		if (*shgrp) {
-			static int ssr_id;
-			static float refract_thickness = 0.0f; /* TODO Param */
-			ssr_id = (stl->effects->use_ssr) ? 0 : -1;
-			add_standard_uniforms(*shgrp, sldata, vedata, &ssr_id, (use_refract) ? &refract_thickness : NULL);
+			static int no_ssr = -1;
+			static int first_ssr = 0;
+			int *ssr_id = (stl->effects->use_ssr && !use_refract) ? &first_ssr : &no_ssr;
+			add_standard_uniforms(*shgrp, sldata, vedata, ssr_id, &ma->refract_depth, use_refract);
 		}
 		else {
 			/* Shader failed : pink color */
@@ -1036,9 +1038,7 @@ static void material_transparent(
 		*shgrp = DRW_shgroup_material_create(*gpumat, psl->transparent_pass);
 		if (*shgrp) {
 			static int ssr_id = -1; /* TODO transparent SSR */
-			static float refract_thickness = 0.0f; /* TODO Param */
-			add_standard_uniforms(*shgrp, sldata, vedata, &ssr_id,
-			        (use_refract) ? &refract_thickness : NULL);
+			add_standard_uniforms(*shgrp, sldata, vedata, &ssr_id, &ma->refract_depth, use_refract);
 		}
 		else {
 			/* Shader failed : pink color */
@@ -1272,7 +1272,7 @@ void EEVEE_materials_cache_populate(EEVEE_Data *vedata, EEVEE_SceneLayerData *sl
 
 									shgrp = DRW_shgroup_material_create(gpumat, psl->material_pass);
 									if (shgrp) {
-										add_standard_uniforms(shgrp, sldata, vedata, NULL, NULL);
+										add_standard_uniforms(shgrp, sldata, vedata, NULL, NULL, false);
 
 										BLI_ghash_insert(material_hash, ma, shgrp);
 
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 b3559e3d366..4ee2e778c21 100644
--- a/source/blender/draw/engines/eevee/shaders/lit_surface_frag.glsl
+++ b/source/blender/draw/engines/eevee/shaders/lit_surface_frag.glsl
@@ -7,9 +7,7 @@ uniform int planar_count;
 uniform bool specToggle;
 uniform bool ssrToggle;
 
-#ifdef USE_REFRACTION
-uniform float refractionThickness;
-#endif
+uniform float refractionDepth;
 
 #ifndef UTIL_TEX
 #define UTIL_TEX
@@ -551,7 +549,7 @@ vec3 eevee_surface_glossy_lit(vec3 N, vec3 f0, float roughness, float ao, int ss
 
 /* ----------- Transmission -----------  */
 
-vec3 eevee_surface_refraction(vec3 N, vec3 f0, float roughness, float ior, int ssr_id, out vec3 ssr_spec)
+vec3 eevee_surface_refraction(vec3 N, vec3 f0, float roughness, float ior)
 {
 	/* Zero length vectors cause issues, see: T51979. */
 #if 0
@@ -581,16 +579,26 @@ vec3 eevee_surface_refraction(vec3 N, vec3 f0, float roughness, float ior, int s
 	/* Accumulate light from all sources until accumulator is full. Then apply Occlusion and BRDF. */
 	vec4 trans_accum = vec4(0.0);
 
+	/* Refract the view vector using the depth heuristic.
+	 * Then later Refract a second time the already refracted
+	 * ray using the inverse ior. */
+	float final_ior = (refractionDepth > 0.0) ? 1.0 / ior : ior;
+	vec3 refr_V = (refractionDepth > 0.0) ? -refract(-V, N, final_ior) : V;
+	vec3 refr_pos = (refractionDepth > 0.0) ? line_plane_intersect(worldPosition, refr_V, worldPosition - N * refractionDepth, N) : worldPosition;
+
 #ifdef USE_REFRACTION
 	/* Screen Space Refraction */
 	if (ssrToggle && roughness < maxRoughness + 0.2) {
 		vec3 rand = texture(utilTex, vec3(gl_FragCoord.xy / LUT_SIZE, 2.0)).xzw;
 
+		/* Find approximated position of the 2nd refraction event. */
+		vec3 refr_vpos = (refractionDepth > 0.0) ? transform_point(ViewMatrix, refr_pos) : viewPosition;
+
 		float ray_ofs = 1.0 / float(rayCount);
-		vec4 spec = screen_space_refraction(viewPosition, N, V, ior, roughnessSquared, rand, 0.0);
-		if (rayCount > 1) spec += screen_space_refraction(viewPosition, N, V, ior, roughnessSquared, rand.xyz * vec3(1.0, -1.0, -1.0), 1.0 * ray_ofs);
-		if (rayCount > 2) spec += screen_space_refraction(viewPosition, N, V, ior, roughnessSquared, rand.xzy * vec3(1.0,  1.0, -1.0), 2.0 * ray_ofs);
-		if (rayCount > 3) spec += screen_space_refraction(viewPosition, N, V, ior, roughnessSquared, rand.xzy * vec3(1.0, -1.0,  1.0), 3.0 * ray_ofs);
+		vec4 spec = screen_space_refraction(refr_vpos, N, refr_V, final_ior, roughnessSquared, rand, 0.0);
+		if (rayCount > 1) spec += screen_space_refraction(refr_vpos, N, refr_V, final_ior, roughnessSquared, rand.xyz * vec3(1.0, -1.0, -1.0), 1.0 * ray_ofs);
+		if (rayCount > 2) spec += screen_space_refraction(refr_vpos, N, refr_V, final_ior, roughnessSquared, rand.xzy * vec3(1.0,  1.0, -1.0), 2.0 * ray_ofs);
+		if (rayCount > 3) spec += screen_space_refraction(refr_vpos, N, refr_V, final_ior, roughnessSquared, rand.xzy * vec3(1.0, -1.0,  1.0), 3.0 * ray_ofs);
 		spec /= float(rayCount);
 		spec.a *= smoothstep(maxRoughness + 0.2, maxRoughness, roughness);
 		accumulate_light(spec.rgb, spec.a, trans_accum);
@@ -599,7 +607,7 @@ vec3 eevee_surface_refraction(vec3 N, vec3 f0, float roughness, float ior, int s
 
 	/* Specular probes */
 	/* NOTE: This bias the IOR */
-	vec3 spec_dir = get_specular_refraction_dominant_dir(N, V, roughness, ior);
+	vec3 refr_dir = get_specular_refraction_dominant_dir(N, refr_V, roughness, final_ior);
 
 	/* Starts at 1 because 0 is world probe */
 	for (int i = 1; i < MAX_PROBE && i < probe_count && trans_accum.a < 0.999; ++i) {
@@ -608,14 +616,14 @@ vec3 eevee_surface_refraction(vec3 N, vec3 f0, float roughness, float ior, int s
 		float fade = probe_attenuation_cube(cd, worldPosition);
 
 		if (fade > 0.0) {
-			vec3 spec = probe_evaluate_cube(float(i), cd, worldPosition, spec_dir, roughnessSquared);
+			vec3 spec = probe_evaluate_cube(float(i), cd, refr_pos, refr_dir, roughnessSquared);
 			accumulate_light(spec, fade, trans_accum);
 		}
 	}
 
 	/* World Specular */
 	if (trans_accum.a < 0.999) {
-		vec3 spec = probe_evaluate_world_spec(spec_dir, roughnessSquared);
+		vec3 spec = probe_evaluate_world_spec(refr_dir, roughnessSquared);
 		accumulate_light(spec, 1.0, trans_accum);
 	}
 
@@ -701,9 +709,13 @@ vec3 eevee_surface_glass(vec3 N, vec3 transmission_col, float roughness, float i
 		}
 	}
 
-	/* Specular probes */
-	vec3 spec_dir = get_specular_reflection_dominant_dir(N, V, roughnessSquared);
-	vec3 refr_dir = get_specular_refraction_dominant_dir(N, V, roughness, ior);
+	/* Refract the view vector using the depth heuristic.
+	 * Then later Refract a second time the already refracted
+	 * ray using the inverse ior. */
+	float final_ior = (refractionDepth > 0.0) ? 1.0 / ior : ior;
+	vec3 refr_V = (refractionDepth > 0.0) ? -refract(-V, N, final_ior) : V;
+	vec3 refr_pos = (refractionDepth > 0.0) ? line_plane_intersect(worldPosition, refr_V, worldPosition - N * refractionDepth, N) : worldPosition;
+
 	vec4 trans_accum = vec4(0.0);
 
 #ifdef USE_REFRACTION
@@ -711,17 +723,24 @@ vec3 eevee_surface_glass(vec3 N, vec3 transmission_col, float roughness, float i
 	if (ssrToggle && roughness < maxRoughness + 0.2) {
 		vec3 rand = texture(utilTex, vec3(gl_FragCoord.xy / LUT_SIZE, 2.0)).xzw;
 
+		/* Find approximated position of the 2nd refraction event. */
+		vec3 refr_vpos = (refractionDepth > 0.0) ? transform_point(ViewMatrix, refr_pos) : viewPosition;
+
 		float ray_ofs = 1.0 / float(rayCount);
-		vec4 spec = screen_space_refraction(viewPosition, N, V, ior, roughnessSquared, rand, 0.0);
-		if (rayCount > 1) spec += screen_space_refraction(viewPosition, N, V, ior, roughnessSquared, rand.xyz * vec3(1.0, -1.0, -1.0), 1.0 * ray_ofs);
-		if (rayCount > 2) spec += screen_space_refraction(viewPosition, N, V, ior, roughnessSquared, rand.xzy * vec3(1.0,  1.0, -1.0), 2.0 * ray_ofs);
-		if (rayCount > 3) spec += screen_space_refraction(viewPosition, N, V, ior, roughnessSquared, rand.xzy * vec3(1.0, -1.0,  1.0), 3.0 * ray_ofs);
+		vec4 spec = screen_space_refraction(refr_vpos, N, refr_V, final_ior, roughnessSquared, rand, 0.0);
+		if (rayCount > 1) spec += screen_space_refraction(refr_vpos, N, refr_V, final_ior, roughnessSquared, rand.xyz * vec3(1.0, -1.0, -1.0), 1.0 * ray_ofs);
+		if (rayCount > 2) spec += screen_space_refraction(refr_vpos, N, refr_V, final_ior, roughnessSquared, rand.xzy * vec3(1.0,  1.0, -1.0), 2.0 * ray_ofs);
+		if (rayCount > 3) spec += screen_space_refraction(refr_vpos, N, refr_V, final_ior, roughnessSquared, rand.xzy * vec3(1.0, -1.0,  1.0), 3.0 * ray_ofs);
 		spec /= float(rayCount);
 		spec.a *= smoothstep(maxRoughness + 0.2, maxRoughness, roughness);
 		accumulate_light(spec.rgb, spec.a, trans_accum);
 	}
 #endif
 
+	/* Specular probes */
+	vec3 refr_dir = get_specular_refraction_dominant_dir(N, refr_V, roughness, final_ior);
+	vec3 spec_dir = get_specular_reflection_dominant_dir(N, V, roughnessSquared);
+
 	/* Starts at 1 because 0 is world probe */
 	for (int i = 1; i < MAX_PROBE && i < probe_count && spec_accum.a < 0.999 && trans_accum.a < 0.999; ++i) {
 		CubeData cd = probes_data[i];
@@ -733,7 +752,7 @@ vec3 eevee_surface_glass(vec3 N, vec3 transmission_col, float roughness, float i
 				vec3 spec = probe_evaluate_cube(float(i), cd, worldPosition, spec_dir, roughness);
 				accumulate_light(spec, fade, spec_accum);
 
-				spec = probe_evaluate_cube(float(i), cd, worldPosition, refr_dir, roughnessSquared);
+				spec = probe_evaluate_cube(float(i), cd, refr_pos, refr_dir, roughnessSquared);
 				accumulate_light(spec, fade, trans_accum);
 			}
 		}