Implemented the full Disney PBR shader
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fbeb0858ac
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1 changed files with 171 additions and 18 deletions
189
shaders/pbr.glsl
189
shaders/pbr.glsl
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@ -1,10 +1,10 @@
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struct T_PBRMaterial
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struct T_PBRMaterialOld
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{
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vec3 cAlbedo, cSpecular;
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float roughness , anisotropy , subsurface , metallic;
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};
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struct T_PBRPrecomputed
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struct T_PBRPrecomputedOld
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{
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float nDotC;
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float ffndc; // Fresnel from n.c
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@ -14,12 +14,12 @@ struct T_PBRPrecomputed
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};
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float PBR_FresnelFrom( in float dotProduct ) {
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float d = clamp( 1.0 - dotProduct , 0.0 , 1.0 );
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return d * d * d * d * d;
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float PBR_FresnelFromOld( in float dotProduct ) {
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float d = clamp( 1.0 - dotProduct , 0 , 1 ) , d2 = d * d;
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return d2 * d2 * d;
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}
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float PBR_GetSpecular( in float cosine , in float alpha )
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float PBR_GetSpecularOld( in float cosine , in float alpha )
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{
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float cs = cosine * cosine;
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float as = alpha * alpha;
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@ -28,15 +28,15 @@ float PBR_GetSpecular( in float cosine , in float alpha )
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// Precompute some of the material's properties. This is independant of the
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// light source.
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T_PBRPrecomputed PBR_Precompute(
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in T_PBRMaterial material ,
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T_PBRPrecomputedOld PBR_PrecomputeOld(
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in T_PBRMaterialOld material ,
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in vec3 rayDir ,
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in vec3 normal )
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{
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T_PBRPrecomputed rv;
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T_PBRPrecomputedOld rv;
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rv.nDotC = dot( normal , rayDir );
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rv.ffndc = PBR_FresnelFrom( rv.nDotC );
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rv.ffndc = PBR_FresnelFromOld( rv.nDotC );
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rv.tangent = cross( vec3( 0. , 1. , 0. ) , normal );
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if ( length( rv.tangent ) == 0.0 ) {
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@ -46,7 +46,7 @@ T_PBRPrecomputed PBR_Precompute(
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rv.bitangent = normalize( cross( normal , rv.tangent ) );
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rv.specAlpha = pow( material.roughness * .5 + .5 , 2. );
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rv.viewSpecular = PBR_GetSpecular( rv.nDotC , rv.specAlpha );
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rv.viewSpecular = PBR_GetSpecularOld( rv.nDotC , rv.specAlpha );
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const float sRoughness = material.roughness * material.roughness;
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const float aspect = sqrt( 1.0 - material.anisotropy * .9 );
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@ -57,9 +57,9 @@ T_PBRPrecomputed PBR_Precompute(
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}
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// Actually compute a light source's contribution
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vec3 PBR_Shade(
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in T_PBRMaterial material ,
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in T_PBRPrecomputed precomputed ,
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vec3 PBR_ShadeOld(
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in T_PBRMaterialOld material ,
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in T_PBRPrecomputedOld precomputed ,
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in vec3 rayDir ,
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in vec3 normal ,
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in vec3 lightDir )
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@ -69,11 +69,15 @@ vec3 PBR_Shade(
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return vec3( 0. );
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}
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// FIXME: should be in common part
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float lSpecular = dot( material.cSpecular , vec3( .3 , .6 , .1 ) );
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vec3 cSpecular = lSpecular > 0 ? ( material.cSpecular / lSpecular ) : vec3( 1 );
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const vec3 halfVec = normalize( lightDir + rayDir );
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const float nDotH = dot( normal , halfVec );
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const float lDotH = dot( lightDir , halfVec );
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const float ffndl = PBR_FresnelFrom( nDotL );
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const float ffndl = PBR_FresnelFromOld( nDotL );
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float grazingDiffuse = lDotH * lDotH * material.roughness;
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float dSubsurface = mix( 1.0 , grazingDiffuse , ffndl )
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* mix( 1.0 , grazingDiffuse , precomputed.ffndc );
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@ -82,9 +86,9 @@ vec3 PBR_Shade(
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const float dFresnel = mix( 1.0 , grazingDiffuse , ffndl )
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* mix( 1.0 , grazingDiffuse , precomputed.ffndc );
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float specular = PBR_GetSpecular( nDotL , precomputed.specAlpha )
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float specular = PBR_GetSpecularOld( nDotL , precomputed.specAlpha )
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* precomputed.viewSpecular;
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specular = mix( specular , 1.0 , PBR_FresnelFrom( lDotH ) );
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specular = mix( specular , 1.0 , PBR_FresnelFromOld( lDotH ) );
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const vec3 d = vec3(
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dot( halfVec , precomputed.tangent ) / precomputed.aAspectX ,
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@ -97,6 +101,155 @@ vec3 PBR_Shade(
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return nDotL * ( material.cAlbedo
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* mix( dFresnel , dSubsurface , material.subsurface )
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* pow( 1.0 - material.metallic , 3 )
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+ specular * material.cSpecular / anisotropic
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+ specular * cSpecular / anisotropic
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);
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}
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// YAY let's do it again!
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const float PI = 3.14159265;
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float PBR_SchlickFresnel( in float u )
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{
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const float m = clamp( 1 - u , 0 , 1 ) ,
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m2 = m * m;
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return m2 * m2 * m;
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}
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float PBR_GTR1( in float nDotH , in float a )
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{
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if (a >= 1) {
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return 1/PI;
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}
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float a2 = a * a ,
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t = 1 + ( a2 - 1 ) * nDotH * nDotH;
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return ( a2 - 1 ) / ( PI * log( a2 ) * t );
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}
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float PBR_GTR2( in float nDotH , in float a )
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{
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float a2 = a * a ,
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t = 1 + ( a2 - 1 ) * nDotH * nDotH;
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return a2 / ( PI * t * t );
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}
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float PBR_GTR2Aniso( in float nDotH ,
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in float hDotX ,
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in float hDotY ,
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in float ax ,
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in float ay )
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{
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float x = hDotX / ax , y = hDotY / ay ,
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p = x * x + y * y + nDotH * nDotH;
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return 1 / ( PI * ax * ay * p * p );
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}
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float PBR_SmithGGX( in float nDotV , in float alpha )
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{
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float a = alpha * alpha , b = nDotV * nDotV;
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return 1 / ( nDotV + sqrt( a + b - a * b ) );
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}
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float PBR_SmithGGXAniso( in float nDotV ,
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in float vDotX ,
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in float vDotY ,
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in float ax ,
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in float ay )
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{
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float x = vDotX * ax , y = vDotY * ay;
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return 1 / ( nDotV + sqrt( x * x + y * y + nDotV * nDotV ) );
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}
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vec3 NormalizeColor( in vec3 color )
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{
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float l = dot( color , vec3( .3 , .6 , .1 ) );
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return l > 0 ? ( color / l ) : vec3( 1 );
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}
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struct T_PBRMaterial
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{
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vec3 cAlbedo;
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float roughness;
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float metallic;
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float subsurface;
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float anisotropy;
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float specular; // Specular strengh for non-metals
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float specularTint; // Albedo color% in specular tint (non-metals)
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};
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vec3 PBR_Shade( in T_PBRMaterial material ,
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in vec3 camDir ,
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in vec3 normal ,
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in vec3 lightDir )
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{
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float nDotL = dot( normal , lightDir ) ,
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nDotV = dot( normal , camDir );
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if ( nDotL < 0 ) return vec3( 1 , 0 , 0 );
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if ( nDotV < 0 ) return vec3( 0 , -nDotV , 0 );
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// if ( nDotL < 0 || nDotV < 0 ) {
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// return vec3( 0 );
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// }
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vec3 tangent = cross( vec3( 0 , 1 , 0 ) , normal );
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if ( length( tangent ) == 0 ) {
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tangent = cross( vec3( 1 , 0 , 0 ) , normal );
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}
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tangent = normalize( tangent );
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vec3 bitangent = normalize( cross( normal , tangent ) );
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vec3 halfVec = normalize( lightDir + camDir ) ,
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tint = NormalizeColor( material.cAlbedo ) ,
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cSpecular = mix( material.specular * .08 * mix(
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vec3( 1 ) , tint , material.specularTint ) ,
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material.cAlbedo , material.metallic );
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//vec3 Csheen = mix(vec3(1), Ctint, sheenTint);
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float nDotH = dot( normal , halfVec ) ,
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lDotH = dot( lightDir , halfVec ) ,
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// Diffuse fresnel - go from 1 at normal incidence to .5 at grazing
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// and mix in diffuse retro-reflection based on roughness
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FL = PBR_SchlickFresnel( nDotL ) ,
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FV = PBR_SchlickFresnel( nDotV ) ,
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Fd90 = 0.5 + 2 * lDotH * lDotH * material.roughness ,
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Fd = mix( 1 , Fd90 , FL ) * mix( 1 , Fd90 , FV ) ,
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// Based on Hanrahan-Krueger brdf approximation of isotropic bssrdf
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// 1.25 scale is used to (roughly) preserve albedo
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// Fss90 used to "flatten" retroreflection based on roughness
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Fss90 = lDotH * lDotH * material.roughness ,
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Fss = mix( 1 , Fss90 , FL ) * mix( 1 , Fss90 , FV ) ,
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ss = 1.25 * ( Fss * ( 1 / ( nDotL + nDotV ) - .5 ) + .5 ) ,
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// Specular
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aspect = sqrt( 1 - material.anisotropy * .9 ) ,
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rsqr = material.roughness * material.roughness ,
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ax = max( .001, rsqr / aspect ) ,
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ay = max( .001, rsqr * aspect ) ,
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Ds = PBR_GTR2Aniso( nDotH , dot( halfVec , tangent ) ,
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dot( halfVec , bitangent ) , ax , ay ) ,
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FH = PBR_SchlickFresnel( lDotH ) ,
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Gs = PBR_SmithGGXAniso( nDotL , dot( lightDir , tangent ) ,
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dot( lightDir , bitangent ) , ax , ay )
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* PBR_SmithGGXAniso( nDotV , dot( camDir , tangent ) ,
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dot( camDir , bitangent ) , ax , ay );
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// sheen
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//vec3 Fsheen = FH * sheen * Csheen;
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// clearcoat (ior = 1.5 -> F0 = 0.04)
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/*
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float Dr = PBR_GTR1( nDotH , mix( .1 , .001 , clearcoatGloss));
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float Fr = mix(.04, 1.0, FH);
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float Gr = smithG_GGX(NdotL, .25) * smithG_GGX(NdotV, .25);
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*/
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vec3 Fs = mix( cSpecular , vec3(1) , FH );
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return nDotL * ( ( ( 1 / PI )
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* mix( Fd , ss , material.subsurface )
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* material.cAlbedo /* + Fsheen */)
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* pow( 1 - material.metallic , 3 )
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+ clamp( Gs , 0 , 1 ) * Fs * Ds );
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//+ .25*clearcoat*Gr*Fr*Dr;
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}
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