Merge pull request #17358 from elalish/remapRoughness

Roughness & environment maps

src/renderers/shaders/ShaderChunk/envmap_physical_pars_fragment.glsl.js

-export default /* glsl */`
+export default /* glsl */ `
 #if defined( USE_ENVMAP )
 
 	#ifdef ENVMAP_MODE_REFRACTION
@@ -44,26 +44,28 @@ export default /* glsl */`
 
 	}
 
-	// taken from here: http://casual-effects.blogspot.ca/2011/08/plausible-environment-lighting-in-two.html
-	float getSpecularMIPLevel( const in float blinnShininessExponent, const in int maxMIPLevel ) {
-
-		//float envMapWidth = pow( 2.0, maxMIPLevelScalar );
-		//float desiredMIPLevel = log2( envMapWidth * sqrt( 3.0 ) ) - 0.5 * log2( pow2( blinnShininessExponent ) + 1.0 );
+	// Trowbridge-Reitz distribution to Mip level, following the logic of http://casual-effects.blogspot.ca/2011/08/plausible-environment-lighting-in-two.html
+	float getSpecularMIPLevel( const in float roughness, const in int maxMIPLevel ) {
 
 		float maxMIPLevelScalar = float( maxMIPLevel );
-		float desiredMIPLevel = maxMIPLevelScalar + 0.79248 - 0.5 * log2( pow2( blinnShininessExponent ) + 1.0 );
+
+		float sigma = PI * roughness * roughness / ( 1.0 + roughness );
+		float desiredMIPLevel = maxMIPLevelScalar + log2( sigma );
 
 		// clamp to allowable LOD ranges.
 		return clamp( desiredMIPLevel, 0.0, maxMIPLevelScalar );
 
 	}
 
-	vec3 getLightProbeIndirectRadiance( /*const in SpecularLightProbe specularLightProbe,*/ const in vec3 viewDir, const in vec3 normal, const in float blinnShininessExponent, const in int maxMIPLevel ) {
+	vec3 getLightProbeIndirectRadiance( /*const in SpecularLightProbe specularLightProbe,*/ const in vec3 viewDir, const in vec3 normal, const in float roughness, const in int maxMIPLevel ) {
 
 		#ifdef ENVMAP_MODE_REFLECTION
 
 		  vec3 reflectVec = reflect( -viewDir, normal );
 
+		  // Mixing the reflection with the normal is more accurate and keeps rough objects from gathering light from behind their tangent plane.
+		  reflectVec = normalize( mix( reflectVec, normal, roughness * roughness) );
+
 		#else
 
 		  vec3 reflectVec = refract( -viewDir, normal, refractionRatio );
@@ -72,7 +74,7 @@ export default /* glsl */`
 
 		reflectVec = inverseTransformDirection( reflectVec, viewMatrix );
 
-		float specularMIPLevel = getSpecularMIPLevel( blinnShininessExponent, maxMIPLevel );
+		float specularMIPLevel = getSpecularMIPLevel( roughness, maxMIPLevel );
 
 		#ifdef ENVMAP_TYPE_CUBE
 
@@ -93,7 +95,7 @@ export default /* glsl */`
 		#elif defined( ENVMAP_TYPE_CUBE_UV )
 
 			vec3 queryReflectVec = vec3( flipEnvMap * reflectVec.x, reflectVec.yz );
-			vec4 envMapColor = textureCubeUV( envMap, queryReflectVec, BlinnExponentToGGXRoughness(blinnShininessExponent ));
+			vec4 envMapColor = textureCubeUV( envMap, queryReflectVec, roughness );
 
 		#elif defined( ENVMAP_TYPE_EQUIREC )
 

src/renderers/shaders/ShaderChunk/lights_fragment_maps.glsl.js

-export default /* glsl */`
+export default /* glsl */ `
 #if defined( RE_IndirectDiffuse )
 
 	#ifdef USE_LIGHTMAP
@@ -25,11 +25,11 @@ export default /* glsl */`
 
 #if defined( USE_ENVMAP ) && defined( RE_IndirectSpecular )
 
-	radiance += getLightProbeIndirectRadiance( /*specularLightProbe,*/ geometry.viewDir, geometry.normal, Material_BlinnShininessExponent( material ), maxMipLevel );
+	radiance += getLightProbeIndirectRadiance( /*specularLightProbe,*/ geometry.viewDir, geometry.normal, material.specularRoughness, maxMipLevel );
 
 	#ifdef CLEARCOAT
 
-		clearcoatRadiance += getLightProbeIndirectRadiance( /*specularLightProbe,*/ geometry.viewDir, geometry.clearcoatNormal, Material_Clearcoat_BlinnShininessExponent( material ), maxMipLevel );
+		clearcoatRadiance += getLightProbeIndirectRadiance( /*specularLightProbe,*/ geometry.viewDir, geometry.clearcoatNormal, material.clearCoatRoughness, maxMipLevel );
 
 	#endif
 

src/renderers/shaders/ShaderChunk/lights_physical_pars_fragment.glsl.js

-export default /* glsl */`
+export default /* glsl */ `
 struct PhysicalMaterial {
 
 	vec3	diffuseColor;
@@ -161,9 +161,6 @@ void RE_IndirectSpecular_Physical( const in vec3 radiance, const in vec3 irradia
 #define RE_IndirectDiffuse		RE_IndirectDiffuse_Physical
 #define RE_IndirectSpecular		RE_IndirectSpecular_Physical
 
-#define Material_BlinnShininessExponent( material )   GGXRoughnessToBlinnExponent( material.specularRoughness )
-#define Material_Clearcoat_BlinnShininessExponent( material )   GGXRoughnessToBlinnExponent( material.clearcoatRoughness )
-
 // ref: https://seblagarde.files.wordpress.com/2015/07/course_notes_moving_frostbite_to_pbr_v32.pdf
 float computeSpecularOcclusion( const in float dotNV, const in float ambientOcclusion, const in float roughness ) {