Scene Shaders - TBN Fixes

Fixes two errors related to the normal, tangent,
and bitangent vectors, namely normals not always
being inverted on backfaces, and normalization
being reversed from what MikkTSpace expects.

drivers/gles3/shaders/scene.glsl

@@ -650,13 +650,16 @@ void main() {
 #endif
 
 	vertex_interp = vertex;
+
+	// Normalize TBN vectors before interpolation, per MikkTSpace.
+	// See: http://www.mikktspace.com/
 #ifdef NORMAL_USED
-	normal_interp = normal;
+	normal_interp = normalize(normal);
 #endif
 
 #if defined(TANGENT_USED) || defined(NORMAL_MAP_USED) || defined(LIGHT_ANISOTROPY_USED)
-	tangent_interp = tangent;
-	binormal_interp = binormal;
+	tangent_interp = normalize(tangent);
+	binormal_interp = normalize(binormal);
 #endif
 
 	// Calculate shadows.
@@ -1799,23 +1802,22 @@ void main() {
 	float alpha = 1.0;
 
 #if defined(TANGENT_USED) || defined(NORMAL_MAP_USED) || defined(LIGHT_ANISOTROPY_USED)
-	vec3 binormal = normalize(binormal_interp);
-	vec3 tangent = normalize(tangent_interp);
+	vec3 binormal = binormal_interp;
+	vec3 tangent = tangent_interp;
 #else
 	vec3 binormal = vec3(0.0);
 	vec3 tangent = vec3(0.0);
 #endif
 
 #ifdef NORMAL_USED
-	vec3 normal = normalize(normal_interp);
-
+	vec3 normal = normal_interp;
 #if defined(DO_SIDE_CHECK)
 	if (!gl_FrontFacing) {
 		normal = -normal;
 	}
-#endif
-
-#endif //NORMAL_USED
+#endif // DO_SIDE_CHECK
+	vec3 geo_normal = normalize(normal);
+#endif // NORMAL_USED
 
 #ifdef UV_USED
 	vec2 uv = uv_interp;
@@ -1900,21 +1902,22 @@ void main() {
 
 #endif // !USE_SHADOW_TO_OPACITY
 
-#ifdef NORMAL_MAP_USED
-
+#if defined(NORMAL_MAP_USED)
 	normal_map.xy = normal_map.xy * 2.0 - 1.0;
 	normal_map.z = sqrt(max(0.0, 1.0 - dot(normal_map.xy, normal_map.xy))); //always ignore Z, as it can be RG packed, Z may be pos/neg, etc.
 
+	// Tangent-space transformation is performed using unnormalized TBN vectors, per MikkTSpace.
+	// See: http://www.mikktspace.com/
 	normal = normalize(mix(normal, tangent * normal_map.x + binormal * normal_map.y + normal * normal_map.z, normal_map_depth));
-
-#endif
+#elif defined(NORMAL_USED)
+	normal = geo_normal;
+#endif // NORMAL_MAP_USED
 
 #ifdef LIGHT_ANISOTROPY_USED
 
 	if (anisotropy > 0.01) {
-		//rotation matrix
-		mat3 rot = mat3(tangent, binormal, normal);
-		//make local to space
+		mat3 rot = mat3(normalize(tangent), normalize(binormal), normal);
+		// Make local to space.
 		tangent = normalize(rot * vec3(anisotropy_flow.x, anisotropy_flow.y, 0.0));
 		binormal = normalize(rot * vec3(-anisotropy_flow.y, anisotropy_flow.x, 0.0));
 	}
@@ -2146,8 +2149,8 @@ void main() {
 				rim, rim_tint,
 #endif
 #ifdef LIGHT_CLEARCOAT_USED
-				clearcoat, clearcoat_roughness, normalize(normal_interp),
-#endif
+				clearcoat, clearcoat_roughness, geo_normal,
+#endif // LIGHT_CLEARCOAT_USED
 #ifdef LIGHT_ANISOTROPY_USED
 				binormal,
 				tangent, anisotropy,
@@ -2172,8 +2175,8 @@ void main() {
 				rim_tint,
 #endif
 #ifdef LIGHT_CLEARCOAT_USED
-				clearcoat, clearcoat_roughness, normalize(normal_interp),
-#endif
+				clearcoat, clearcoat_roughness, geo_normal,
+#endif // LIGHT_CLEARCOAT_USED
 #ifdef LIGHT_ANISOTROPY_USED
 				binormal, tangent, anisotropy,
 #endif
@@ -2196,8 +2199,8 @@ void main() {
 				rim_tint,
 #endif
 #ifdef LIGHT_CLEARCOAT_USED
-				clearcoat, clearcoat_roughness, normalize(normal_interp),
-#endif
+				clearcoat, clearcoat_roughness, geo_normal,
+#endif // LIGHT_CLEARCOAT_USED
 #ifdef LIGHT_ANISOTROPY_USED
 				tangent,
 				binormal, anisotropy,
@@ -2448,8 +2451,8 @@ void main() {
 			rim, rim_tint,
 #endif
 #ifdef LIGHT_CLEARCOAT_USED
-			clearcoat, clearcoat_roughness, normalize(normal_interp),
-#endif
+			clearcoat, clearcoat_roughness, geo_normal,
+#endif // LIGHT_CLEARCOAT_USED
 #ifdef LIGHT_ANISOTROPY_USED
 			binormal,
 			tangent, anisotropy,
@@ -2481,8 +2484,8 @@ void main() {
 			rim_tint,
 #endif
 #ifdef LIGHT_CLEARCOAT_USED
-			clearcoat, clearcoat_roughness, normalize(normal_interp),
-#endif
+			clearcoat, clearcoat_roughness, geo_normal,
+#endif // LIGHT_CLEARCOAT_USED
 #ifdef LIGHT_ANISOTROPY_USED
 			binormal, tangent, anisotropy,
 #endif
@@ -2511,8 +2514,8 @@ void main() {
 			rim_tint,
 #endif
 #ifdef LIGHT_CLEARCOAT_USED
-			clearcoat, clearcoat_roughness, normalize(normal_interp),
-#endif
+			clearcoat, clearcoat_roughness, geo_normal,
+#endif // LIGHT_RIM_USED
 #ifdef LIGHT_ANISOTROPY_USED
 			tangent,
 			binormal, anisotropy,

servers/rendering/renderer_rd/shaders/forward_clustered/scene_forward_clustered.glsl

@@ -457,13 +457,15 @@ void vertex_shader(vec3 vertex_input,
 
 	vertex_interp = vertex;
 
+	// Normalize TBN vectors before interpolation, per MikkTSpace.
+	// See: http://www.mikktspace.com/
 #ifdef NORMAL_USED
-	normal_interp = normal;
+	normal_interp = normalize(normal);
 #endif
 
 #ifdef TANGENT_USED
-	tangent_interp = tangent;
-	binormal_interp = binormal;
+	tangent_interp = normalize(tangent);
+	binormal_interp = normalize(binormal);
 #endif
 
 #ifdef MODE_RENDER_DEPTH
@@ -1158,23 +1160,22 @@ void fragment_shader(in SceneData scene_data) {
 	float alpha = float(instances.data[instance_index].flags >> INSTANCE_FLAGS_FADE_SHIFT) / float(255.0);
 
 #ifdef TANGENT_USED
-	vec3 binormal = normalize(binormal_interp);
-	vec3 tangent = normalize(tangent_interp);
+	vec3 binormal = binormal_interp;
+	vec3 tangent = tangent_interp;
 #else
 	vec3 binormal = vec3(0.0);
 	vec3 tangent = vec3(0.0);
 #endif
 
 #ifdef NORMAL_USED
-	vec3 normal = normalize(normal_interp);
-
+	vec3 normal = normal_interp;
 #if defined(DO_SIDE_CHECK)
 	if (!gl_FrontFacing) {
 		normal = -normal;
 	}
-#endif
-
-#endif //NORMAL_USED
+#endif // DO_SIDE_CHECK
+	vec3 geo_normal = normalize(normal);
+#endif // NORMAL_USED
 
 #ifdef UV_USED
 	vec2 uv = uv_interp;
@@ -1292,21 +1293,22 @@ void fragment_shader(in SceneData scene_data) {
 
 #endif // !USE_SHADOW_TO_OPACITY
 
-#ifdef NORMAL_MAP_USED
-
+#if defined(NORMAL_MAP_USED)
 	normal_map.xy = normal_map.xy * 2.0 - 1.0;
 	normal_map.z = sqrt(max(0.0, 1.0 - dot(normal_map.xy, normal_map.xy))); //always ignore Z, as it can be RG packed, Z may be pos/neg, etc.
 
+	// Tangent-space transformation is performed using unnormalized TBN vectors, per MikkTSpace.
+	// See: http://www.mikktspace.com/
 	normal = normalize(mix(normal, tangent * normal_map.x + binormal * normal_map.y + normal * normal_map.z, normal_map_depth));
-
-#endif
+#elif defined(NORMAL_USED)
+	normal = geo_normal;
+#endif // NORMAL_MAP_USED
 
 #ifdef LIGHT_ANISOTROPY_USED
 
 	if (anisotropy > 0.01) {
-		//rotation matrix
-		mat3 rot = mat3(tangent, binormal, normal);
-		//make local to space
+		mat3 rot = mat3(normalize(tangent), normalize(binormal), normal);
+		// Make local to space.
 		tangent = normalize(rot * vec3(anisotropy_flow.x, anisotropy_flow.y, 0.0));
 		binormal = normalize(rot * vec3(-anisotropy_flow.y, anisotropy_flow.x, 0.0));
 	}
@@ -1426,7 +1428,7 @@ void fragment_shader(in SceneData scene_data) {
 				float fade = pow(1.0 - (uv_local.y > 0.0 ? uv_local.y : -uv_local.y), uv_local.y > 0.0 ? decals.data[decal_index].upper_fade : decals.data[decal_index].lower_fade);
 
 				if (decals.data[decal_index].normal_fade > 0.0) {
-					fade *= smoothstep(decals.data[decal_index].normal_fade, 1.0, dot(normal_interp, decals.data[decal_index].normal) * 0.5 + 0.5);
+					fade *= smoothstep(decals.data[decal_index].normal_fade, 1.0, dot(geo_normal, decals.data[decal_index].normal) * 0.5 + 0.5);
 				}
 
 				//we need ddx/ddy for mipmaps, so simulate them
@@ -1576,16 +1578,15 @@ void fragment_shader(in SceneData scene_data) {
 #ifdef LIGHT_CLEARCOAT_USED
 
 	if (scene_data.use_reflection_cubemap) {
-		vec3 n = normalize(normal_interp); // We want to use geometric normal, not normal_map
-		float NoV = max(dot(n, view), 0.0001);
-		vec3 ref_vec = reflect(-view, n);
+		float NoV = max(dot(geo_normal, view), 0.0001); // We want to use geometric normal, not normal_map
+		vec3 ref_vec = reflect(-view, geo_normal);
+		ref_vec = mix(ref_vec, geo_normal, clearcoat_roughness * clearcoat_roughness);
 		// The clear coat layer assumes an IOR of 1.5 (4% reflectance)
 		float Fc = clearcoat * (0.04 + 0.96 * SchlickFresnel(NoV));
 		float attenuation = 1.0 - Fc;
 		ambient_light *= attenuation;
 		specular_light *= attenuation;
 
-		ref_vec = mix(ref_vec, n, clearcoat_roughness * clearcoat_roughness);
 		float horizon = min(1.0 + dot(ref_vec, normal), 1.0);
 		ref_vec = scene_data.radiance_inverse_xform * ref_vec;
 		float roughness_lod = mix(0.001, 0.1, sqrt(clearcoat_roughness)) * MAX_ROUGHNESS_LOD;
@@ -2026,7 +2027,7 @@ void fragment_shader(in SceneData scene_data) {
 				if (directional_lights.data[i].shadow_opacity > 0.001) {
 					float depth_z = -vertex.z;
 					vec3 light_dir = directional_lights.data[i].direction;
-					vec3 base_normal_bias = normalize(normal_interp) * (1.0 - max(0.0, dot(light_dir, -normalize(normal_interp))));
+					vec3 base_normal_bias = geo_normal * (1.0 - max(0.0, dot(light_dir, -geo_normal)));
 
 #define BIAS_FUNC(m_var, m_idx)                                                                 \
 	m_var.xyz += light_dir * directional_lights.data[i].shadow_bias[m_idx];                     \
@@ -2270,7 +2271,7 @@ void fragment_shader(in SceneData scene_data) {
 				float depth_z = -vertex.z;
 
 				if (depth_z < directional_lights.data[i].shadow_split_offsets.x) {
-					vec4 trans_vertex = vec4(vertex - normalize(normal_interp) * directional_lights.data[i].shadow_transmittance_bias.x, 1.0);
+					vec4 trans_vertex = vec4(vertex - geo_normal * directional_lights.data[i].shadow_transmittance_bias.x, 1.0);
 					vec4 trans_coord = directional_lights.data[i].shadow_matrix1 * trans_vertex;
 					trans_coord /= trans_coord.w;
 
@@ -2280,7 +2281,7 @@ void fragment_shader(in SceneData scene_data) {
 
 					transmittance_z = z - shadow_z;
 				} else if (depth_z < directional_lights.data[i].shadow_split_offsets.y) {
-					vec4 trans_vertex = vec4(vertex - normalize(normal_interp) * directional_lights.data[i].shadow_transmittance_bias.y, 1.0);
+					vec4 trans_vertex = vec4(vertex - geo_normal * directional_lights.data[i].shadow_transmittance_bias.y, 1.0);
 					vec4 trans_coord = directional_lights.data[i].shadow_matrix2 * trans_vertex;
 					trans_coord /= trans_coord.w;
 
@@ -2290,7 +2291,7 @@ void fragment_shader(in SceneData scene_data) {
 
 					transmittance_z = z - shadow_z;
 				} else if (depth_z < directional_lights.data[i].shadow_split_offsets.z) {
-					vec4 trans_vertex = vec4(vertex - normalize(normal_interp) * directional_lights.data[i].shadow_transmittance_bias.z, 1.0);
+					vec4 trans_vertex = vec4(vertex - geo_normal * directional_lights.data[i].shadow_transmittance_bias.z, 1.0);
 					vec4 trans_coord = directional_lights.data[i].shadow_matrix3 * trans_vertex;
 					trans_coord /= trans_coord.w;
 
@@ -2299,9 +2300,8 @@ void fragment_shader(in SceneData scene_data) {
 					float z = trans_coord.z * directional_lights.data[i].shadow_z_range.z;
 
 					transmittance_z = z - shadow_z;
-
 				} else {
-					vec4 trans_vertex = vec4(vertex - normalize(normal_interp) * directional_lights.data[i].shadow_transmittance_bias.w, 1.0);
+					vec4 trans_vertex = vec4(vertex - geo_normal * directional_lights.data[i].shadow_transmittance_bias.w, 1.0);
 					vec4 trans_coord = directional_lights.data[i].shadow_matrix4 * trans_vertex;
 					trans_coord /= trans_coord.w;
 
@@ -2365,8 +2365,8 @@ void fragment_shader(in SceneData scene_data) {
 					rim, rim_tint,
 #endif
 #ifdef LIGHT_CLEARCOAT_USED
-					clearcoat, clearcoat_roughness, normalize(normal_interp),
-#endif
+					clearcoat, clearcoat_roughness, geo_normal,
+#endif // LIGHT_CLEARCOAT_USED
 #ifdef LIGHT_ANISOTROPY_USED
 					binormal,
 					tangent, anisotropy,
@@ -2435,8 +2435,8 @@ void fragment_shader(in SceneData scene_data) {
 						rim_tint,
 #endif
 #ifdef LIGHT_CLEARCOAT_USED
-						clearcoat, clearcoat_roughness, normalize(normal_interp),
-#endif
+						clearcoat, clearcoat_roughness, geo_normal,
+#endif // LIGHT_CLEARCOAT_USED
 #ifdef LIGHT_ANISOTROPY_USED
 						tangent, binormal, anisotropy,
 #endif
@@ -2503,8 +2503,8 @@ void fragment_shader(in SceneData scene_data) {
 						rim_tint,
 #endif
 #ifdef LIGHT_CLEARCOAT_USED
-						clearcoat, clearcoat_roughness, normalize(normal_interp),
-#endif
+						clearcoat, clearcoat_roughness, geo_normal,
+#endif // LIGHT_CLEARCOAT_USED
 #ifdef LIGHT_ANISOTROPY_USED
 						tangent,
 						binormal, anisotropy,
@@ -2553,7 +2553,7 @@ void fragment_shader(in SceneData scene_data) {
 				vec3(0, -1, 0),
 				vec3(0, 0, -1));
 
-		vec3 cam_normal = mat3(scene_data.inv_view_matrix) * normalize(normal_interp);
+		vec3 cam_normal = mat3(scene_data.inv_view_matrix) * geo_normal;
 
 		float closest_dist = -1e20;
 

servers/rendering/renderer_rd/shaders/forward_mobile/scene_forward_mobile.glsl

@@ -433,6 +433,9 @@ void main() {
 #endif
 
 	vertex_interp = vertex;
+
+	// Normalize TBN vectors before interpolation, per MikkTSpace.
+	// See: http://www.mikktspace.com/
 #ifdef NORMAL_USED
 	normal_interp = normalize(normal);
 #endif
@@ -881,23 +884,22 @@ void main() {
 	float alpha = 1.0;
 
 #if defined(TANGENT_USED) || defined(NORMAL_MAP_USED) || defined(LIGHT_ANISOTROPY_USED)
-	vec3 binormal = normalize(binormal_interp);
-	vec3 tangent = normalize(tangent_interp);
-#else
+	vec3 binormal = binormal_interp;
+	vec3 tangent = tangent_interp;
+#else // TANGENT_USED || NORMAL_MAP_USED || LIGHT_ANISOTROPY_USED
 	vec3 binormal = vec3(0.0);
 	vec3 tangent = vec3(0.0);
 #endif
 
 #ifdef NORMAL_USED
-	vec3 normal = normalize(normal_interp);
-
+	vec3 normal = normal_interp;
 #if defined(DO_SIDE_CHECK)
 	if (!gl_FrontFacing) {
 		normal = -normal;
 	}
-#endif
-
-#endif //NORMAL_USED
+#endif // DO_SIDE_CHECK
+	vec3 geo_normal = normalize(normal);
+#endif // NORMAL_USED
 
 #ifdef UV_USED
 	vec2 uv = uv_interp;
@@ -1020,21 +1022,22 @@ void main() {
 
 #endif // !USE_SHADOW_TO_OPACITY
 
-#ifdef NORMAL_MAP_USED
-
+#if defined(NORMAL_MAP_USED)
 	normal_map.xy = normal_map.xy * 2.0 - 1.0;
 	normal_map.z = sqrt(max(0.0, 1.0 - dot(normal_map.xy, normal_map.xy))); //always ignore Z, as it can be RG packed, Z may be pos/neg, etc.
 
+	// Tangent-space transformation is performed using unnormalized TBN vectors, per MikkTSpace.
+	// See: http://www.mikktspace.com/
 	normal = normalize(mix(normal, tangent * normal_map.x + binormal * normal_map.y + normal * normal_map.z, normal_map_depth));
-
-#endif
+#elif defined(NORMAL_USED)
+	normal = geo_normal;
+#endif // NORMAL_MAP_USED
 
 #ifdef LIGHT_ANISOTROPY_USED
 
 	if (anisotropy > 0.01) {
-		//rotation matrix
-		mat3 rot = mat3(tangent, binormal, normal);
-		//make local to space
+		mat3 rot = mat3(normalize(tangent), normalize(binormal), normal);
+		// Make local to space.
 		tangent = normalize(rot * vec3(anisotropy_flow.x, anisotropy_flow.y, 0.0));
 		binormal = normalize(rot * vec3(-anisotropy_flow.y, anisotropy_flow.x, 0.0));
 	}
@@ -1091,7 +1094,7 @@ void main() {
 		float fade = pow(1.0 - (uv_local.y > 0.0 ? uv_local.y : -uv_local.y), uv_local.y > 0.0 ? decals.data[decal_index].upper_fade : decals.data[decal_index].lower_fade);
 
 		if (decals.data[decal_index].normal_fade > 0.0) {
-			fade *= smoothstep(decals.data[decal_index].normal_fade, 1.0, dot(normal_interp, decals.data[decal_index].normal) * 0.5 + 0.5);
+			fade *= smoothstep(decals.data[decal_index].normal_fade, 1.0, dot(geo_normal, decals.data[decal_index].normal) * 0.5 + 0.5);
 		}
 
 		//we need ddx/ddy for mipmaps, so simulate them
@@ -1238,10 +1241,9 @@ void main() {
 #ifdef LIGHT_CLEARCOAT_USED
 
 	if (sc_scene_use_reflection_cubemap()) {
-		vec3 n = normalize(normal_interp); // We want to use geometric normal, not normal_map
-		float NoV = max(dot(n, view), 0.0001);
-		vec3 ref_vec = reflect(-view, n);
-		ref_vec = mix(ref_vec, n, clearcoat_roughness * clearcoat_roughness);
+		float NoV = max(dot(geo_normal, view), 0.0001); // We want to use geometric normal, not normal_map
+		vec3 ref_vec = reflect(-view, geo_normal);
+		ref_vec = mix(ref_vec, geo_normal, clearcoat_roughness * clearcoat_roughness);
 		// The clear coat layer assumes an IOR of 1.5 (4% reflectance)
 		float Fc = clearcoat * (0.04 + 0.96 * SchlickFresnel(NoV));
 		float attenuation = 1.0 - Fc;
@@ -1481,7 +1483,7 @@ void main() {
 					vec4 pssm_coord;
 					float blur_factor;
 					vec3 light_dir = directional_lights.data[i].direction;
-					vec3 base_normal_bias = normalize(normal_interp) * (1.0 - max(0.0, dot(light_dir, -normalize(normal_interp))));
+					vec3 base_normal_bias = geo_normal * (1.0 - max(0.0, dot(light_dir, -geo_normal)));
 
 #define BIAS_FUNC(m_var, m_idx)                                                                 \
 	m_var.xyz += light_dir * directional_lights.data[i].shadow_bias[m_idx];                     \
@@ -1663,8 +1665,8 @@ void main() {
 					rim, rim_tint,
 #endif
 #ifdef LIGHT_CLEARCOAT_USED
-					clearcoat, clearcoat_roughness, normalize(normal_interp),
-#endif
+					clearcoat, clearcoat_roughness, geo_normal,
+#endif // LIGHT_CLEARCOAT_USED
 #ifdef LIGHT_ANISOTROPY_USED
 					binormal, tangent, anisotropy,
 #endif
@@ -1694,8 +1696,8 @@ void main() {
 				rim_tint,
 #endif
 #ifdef LIGHT_CLEARCOAT_USED
-				clearcoat, clearcoat_roughness, normalize(normal_interp),
-#endif
+				clearcoat, clearcoat_roughness, geo_normal,
+#endif // LIGHT_CLEARCOAT_USED
 #ifdef LIGHT_ANISOTROPY_USED
 				tangent,
 				binormal, anisotropy,
@@ -1722,8 +1724,8 @@ void main() {
 				rim_tint,
 #endif
 #ifdef LIGHT_CLEARCOAT_USED
-				clearcoat, clearcoat_roughness, normalize(normal_interp),
-#endif
+				clearcoat, clearcoat_roughness, geo_normal,
+#endif // LIGHT_CLEARCOAT_USED
 #ifdef LIGHT_ANISOTROPY_USED
 				tangent,
 				binormal, anisotropy,