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#ifndef MICROFACET_BSDF_GLSLLIB
#define MICROFACET_BSDF_GLSLLIB 1
float GtermSchlick( in mat3 tanFrame, in vec3 l, in vec3 v, in float roughness )
{
float NdotV = clamp(dot(tanFrame[2], v), 0.0, 1.0);
float NdotL = clamp(dot(tanFrame[2], l), 0.0, 1.0);
float k = roughness*roughness*0.79788;
float G_V = NdotV / (NdotV * (1.0 + k) + k);
float G_L = NdotL / (NdotL * (1.0 + k) + k);
return clamp(( G_V * G_L ), 0.0, 1.0);
}
float GtermGGX( in mat3 tanFrame, in vec3 l, in vec3 v, in float roughness )
{
float NdotV = clamp(dot(tanFrame[2], v), 0.0, 1.0);
float NdotL = clamp(dot(tanFrame[2], l), 0.0, 1.0);
float k = clamp(roughness*roughness, 0.00, 1.0);
float G_V = NdotV + sqrt( (NdotV - NdotV * k) * NdotV + k );
float G_L = NdotL + sqrt( (NdotL - NdotL * k) * NdotL + k );
return clamp( 2.0 / ( G_V * G_L ), 0.0, 1.0);
}
float DtermGGX( in mat3 tanFrame, in vec3 L, in vec3 V, in float roughness )
{
float m = clamp(roughness, 0.04, 1.0);
float m2 = m*m;
vec3 H = normalize(L + V);
float NdotH = clamp(dot( tanFrame[2], H ), 0.0001, 1.0);
float NdotH2 = NdotH * NdotH;
float denom = NdotH2 * (m2 - 1.0) + 1.0;
float D = m2 / (PI * denom * denom);
return max( 0.0, D);
}
float DtermGGXAniso( in mat3 tanFrame, in vec3 L, in vec3 V, in float roughnessU, float roughnessV )
{
float roughU = clamp(roughnessU, 0.04, 1.0);
float roughV = clamp(roughnessV, 0.04, 1.0);
vec3 H = normalize(L + V);
float NdotH = clamp( dot(tanFrame[2], H), 0.0001, 1.0 );
float m = PI * roughU * roughV;
float HdotX = clamp( abs(dot(H, tanFrame[0])), 0.0001, 1.0 );
float HdotY = clamp( abs(dot(H, tanFrame[1])), 0.0001, 1.0 );
float x2 = roughU*roughU;
float y2 = roughV*roughV;
float D = (HdotX*HdotX/x2) + (HdotY*HdotY/y2) + (NdotH*NdotH);
D = 1.0 / ( m * D * D );
return max( 0.0, D);
}
vec4 microfacetBSDF( in mat3 tanFrame, in vec3 L, in vec3 V, in vec3 lightSpecular, float ior,
in float roughnessU, in float roughnessV, int mode )
{
vec4 rgba = vec4( 0.0f, 0.0f, 0.0f, 1.0f );
vec3 H = normalize(L + V);
float HdotL = clamp(dot(H, L), 0.0, 1.0);
float NdotL = dot(tanFrame[2], L);
if ( NdotL > 0.0 )
{
if ( ( mode == scatter_reflect ) || ( mode == scatter_reflect_transmit ) )
{
float roughness = calculateRoughness( tanFrame[2], roughnessU, roughnessV, tanFrame[0] );
// G term
//float G = GtermSchlick( tanFrame, L, V, roughness );
float G = GtermGGX( tanFrame, L, V, roughness );
//float D = DtermGGX( tanFrame, L, V, roughness );
float D = DtermGGXAniso( tanFrame, L, V, roughnessU, roughnessV );
rgba.rgb = G * D * NdotL * lightSpecular;
}
if ( ( mode == scatter_transmit ) || ( mode == scatter_reflect_transmit ) )
{
rgba.a = pow(1.0 - clamp(HdotL, 0.0, 1.0), 5.0);
}
}
return rgba;
}
vec4 microfacetBSDFEnvironment( in mat3 tanFrame, in vec3 viewDir, in float roughnessU, in float roughnessV, int mode )
{
vec3 rgb = vec3( 0.0f, 0.0f, 0.0f );
#if !UIC_ENABLE_LIGHT_PROBE
if ( uEnvironmentMappingEnabled )
{
float roughness = calculateRoughness( tanFrame[2], roughnessU, roughnessV, tanFrame[0] );
vec3 R = reflect( -viewDir, tanFrame[2] );
rgb = 0.01 * evalEnvironmentMap( R, roughness );
rgb = microfacetBSDF( tanFrame, R, viewDir, rgb, 1.0f, roughnessU, roughnessV, scatter_reflect ).rgb;
}
#endif
return( vec4( rgb, 1.0f ) );
}
// see http://holger.dammertz.org/stuff/notes_HammersleyOnHemisphere.html
float radicalInverse_VdC( uint bits)
{
bits = (bits << 16u) | (bits >> 16u);
bits = ((bits & 0x55555555u) << 1u) | ((bits & 0xAAAAAAAAu) >> 1u);
bits = ((bits & 0x33333333u) << 2u) | ((bits & 0xCCCCCCCCu) >> 2u);
bits = ((bits & 0x0F0F0F0Fu) << 4u) | ((bits & 0xF0F0F0F0u) >> 4u);
bits = ((bits & 0x00FF00FFu) << 8u) | ((bits & 0xFF00FF00u) >> 8u);
return float(bits) * 2.3283064365386963e-10; // / 0x100000000
}
vec2 hammersley2d(uint i, uint N)
{
return vec2(float(i)/float(N), radicalInverse_VdC(i));
}
vec2 hammersly[4] = vec2[4] (
vec2(0.0, 0.0),
vec2(0.25, 0.5),
vec2(0.5, 0.25),
vec2(0.75, 0.75)
);
vec3 ImportanceGGX( in mat3 tanFrame, vec2 Xi, float roughness , vec3 N )
{
float a = roughness * roughness;
float Phi = 2.0 * PI * Xi.y;
float CosTheta = (1.0 - Xi.x);
float SinTheta = sqrt( 1.0 - CosTheta * CosTheta );
vec3 H;
H.x = SinTheta * cos( Phi );
H.y = SinTheta * sin( Phi );
H.z = CosTheta;
// Tangent to world space
return tanFrame[0] * H.x + tanFrame[1] * H.y + tanFrame[2] * H.z;
}
float DtermGGXAnisoSampled( in mat3 tanFrame, in vec3 H, in float roughnessU, float roughnessV )
{
#if (MATERIAL_IS_NON_DIELECTRIC == 1)
float roughU = clamp(roughnessU*roughnessU, 0.01, 1.0);
float roughV = clamp(roughnessV*roughnessV, 0.01, 1.0);
#else
float roughU = clamp(roughnessU, 0.02, 1.0);
float roughV = clamp(roughnessV, 0.02, 1.0);
#endif
float NdotH = clamp( dot(tanFrame[2], H), 0.0001, 1.0 );
float m = PI * roughU * roughV;
float HdotX = clamp( abs(dot(H, tanFrame[0])), 0.0001, 1.0 );
float HdotY = clamp( abs(dot(H, tanFrame[1])), 0.0001, 1.0 );
float x2 = roughU*roughU;
float y2 = roughV*roughV;
float pdf = (HdotX*HdotX/x2) + (HdotY*HdotY/y2) + (NdotH*NdotH);
float D = 1.0 / ( m * pdf * pdf );
return max( 0.0, D);
}
vec3 sampleEnv(in vec3 L, float pdf, uint sampleCount, float roughness )
{
vec2 envMapSize = vec2( textureSize( uEnvironmentTexture, 0 ) );
float envMapLevels = log2( max( envMapSize.x, envMapSize.y ) );
float a = 0.5*log2( float(envMapSize.x*envMapSize.y) / float(sampleCount) );
float d = 4.0 * (abs(L.z) + 1.0) * (abs(L.z) + 1.0);
float b = 0.5*log2( pdf * d );
// convert coord to 2D
vec2 tc = vec2( ( atan( L.x, -L.z ) + PI ) / ( 2.0f * PI ), acos( -L.y ) / PI );
float weight = step( 0.0001, roughness );
float lod = max( 0.0, min( (a - b)*weight, envMapLevels ));
return( textureLod( uEnvironmentTexture, tc, lod ).rgb );
}
vec4 microfacetSampledBSDF( in mat3 tanFrame, in vec3 viewDir, in float roughnessU, in float roughnessV, int mode )
{
vec3 rgb = vec3( 0.0f, 0.0f, 0.0f );
float roughness = clamp( calculateRoughness( tanFrame[2], roughnessU, roughnessV, tanFrame[0] ), 0.0, 1.0 );
vec3 R = reflect( -viewDir, tanFrame[2] );
const uint NumSamples = 4u;
for( uint i = 0u; i < NumSamples; i++ )
{
vec2 Xi = hammersly[i]; // pre computed values
//vec2 Xi = hammersley2d(i, NumSamples);
vec3 Half = ImportanceGGX( tanFrame, Xi, roughness , tanFrame[2] );
vec3 H = normalize( Half );
vec3 L = 2.0 * dot( viewDir, Half ) * Half - viewDir;
float NdotV = clamp( dot( tanFrame[2], viewDir ), 0.0001, 1.0 );
float NdotR = clamp( dot( tanFrame[2], R ), 0.0, 1.0 );
float NdotH = clamp( dot( tanFrame[2], H ), 0.0001, 1.0 );
if( NdotV > 0.0001 )
{
float G = GtermGGX( tanFrame, L, viewDir, roughness );
float D = DtermGGXAnisoSampled( tanFrame, H, roughnessU, roughnessV);
vec3 envColor = 0.01 * sampleEnv( L, D, NumSamples, roughness );
rgb += (envColor * G * D * NdotR) / ( 4.0 * NdotV * NdotH);
}
}
rgb /= float(NumSamples);
return( vec4( rgb, 1.0f ) );
}
#endif
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