\t}\n\tfloat w2( float a ){\n\t\treturn ( 1.0 / 6.0 ) * ( a * ( a * ( - 3.0 * a + 3.0 ) + 3.0 ) + 1.0 );\n\t}\n\tfloat w3( float a ) {\n\t\treturn ( 1.0 / 6.0 ) * ( a * a * a );\n\t}\n\tfloat g0( float a ) {\n\t\treturn w0( a ) + w1( a );\n\t}\n\tfloat g1( float a ) {\n\t\treturn w2( a ) + w3( a );\n\t}\n\tfloat h0( float a ) {\n\t\treturn - 1.0 + w1( a ) / ( w0( a ) + w1( a ) );\n\t}\n\tfloat h1( float a ) {\n\t\treturn 1.0 + w3( a ) / ( w2( a ) + w3( a ) );\n\t}\n\tvec4 bicubic( sampler2D tex, vec2 uv, vec4 texelSize, float lod ) {\n\t\tuv = uv * texelSize.zw + 0.5;\n\t\tvec2 iuv = floor( uv );\n\t\tvec2 fuv = fract( uv );\n\t\tfloat g0x = g0( fuv.x );\n\t\tfloat g1x = g1( fuv.x );\n\t\tfloat h0x = h0( fuv.x );\n\t\tfloat h1x = h1( fuv.x );\n\t\tfloat h0y = h0( fuv.y );\n\t\tfloat h1y = h1( fuv.y );\n\t\tvec2 p0 = ( vec2( iuv.x + h0x, iuv.y + h0y ) - 0.5 ) * texelSize.xy;\n\t\tvec2 p1 = ( vec2( iuv.x + h1x, iuv.y + h0y ) - 0.5 ) * texelSize.xy;\n\t\tvec2 p2 = ( vec2( iuv.x + h0x, iuv.y + h1y ) - 0.5 ) * texelSize.xy;\n\t\tvec2 p3 = ( vec2( iuv.x + h1x, iuv.y + h1y ) - 0.5 ) * texelSize.xy;\n\t\treturn g0( fuv.y ) * ( g0x * textureLod( tex, p0, lod ) + g1x * textureLod( tex, p1, lod ) ) +\n\t\t\tg1( fuv.y ) * ( g0x * textureLod( tex, p2, lod ) + g1x * textureLod( tex, p3, lod ) );\n\t}\n\tvec4 textureBicubic( sampler2D sampler, vec2 uv, float lod ) {\n\t\tvec2 fLodSize = vec2( textureSize( sampler, int( lod ) ) );\n\t\tvec2 cLodSize = vec2( textureSize( sampler, int( lod + 1.0 ) ) );\n\t\tvec2 fLodSizeInv = 1.0 / fLodSize;\n\t\tvec2 cLodSizeInv = 1.0 / cLodSize;\n\t\tvec4 fSample = bicubic( sampler, uv, vec4( fLodSizeInv, fLodSize ), floor( lod ) );\n\t\tvec4 cSample = bicubic( sampler, uv, vec4( cLodSizeInv, cLodSize ), ceil( lod ) );\n\t\treturn mix( fSample, cSample, fract( lod ) );\n\t}\n\tvec3 getVolumeTransmissionRay( const in vec3 n, const in vec3 v, const in float thickness, const in float ior, const in mat4 modelMatrix ) {\n\t\tvec3 refractionVector = refract( - v, normalize( n ), 1.0 / ior );\n\t\tvec3 modelScale;\n\t\tmodelScale.x = length( vec3( modelMatrix[ 0 ].xyz ) );\n\t\tmodelScale.y = length( vec3( modelMatrix[ 1 ].xyz ) );\n\t\tmodelScale.z = length( vec3( modelMatrix[ 2 ].xyz ) );\n\t\treturn normalize( refractionVector ) * thickness * modelScale;\n\t}\n\tfloat applyIorToRoughness( const in float roughness, const in float ior ) {\n\t\treturn roughness * clamp( ior * 2.0 - 2.0, 0.0, 1.0 );\n\t}\n\tvec4 getTransmissionSample( const in vec2 fragCoord, const in float roughness, const in float ior ) {\n\t\tfloat lod = log2( transmissionSamplerSize.x ) * applyIorToRoughness( roughness, ior );\n\t\treturn textureBicubic( transmissionSamplerMap, fragCoord.xy, lod );\n\t}\n\tvec3 volumeAttenuation( const in float transmissionDistance, const in vec3 attenuationColor, const in float attenuationDistance ) {\n\t\tif ( isinf( attenuationDistance ) ) {\n\t\t\treturn vec3( 1.0 );\n\t\t} else {\n\t\t\tvec3 attenuationCoefficient = -log( attenuationColor ) / attenuationDistance;\n\t\t\tvec3 transmittance = exp( - attenuationCoefficient * transmissionDistance );\t\t\treturn transmittance;\n\t\t}\n\t}\n\tvec4 getIBLVolumeRefraction( const in vec3 n, const in vec3 v, const in float roughness, const in vec3 diffuseColor,\n\t\tconst in vec3 specularColor, const in float specularF90, const in vec3 position, const in mat4 modelMatrix,\n\t\tconst in mat4 viewMatrix, const in mat4 projMatrix, const in float dispersion, const in float ior, const in float thickness,\n\t\tconst in vec3 attenuationColor, const in float attenuationDistance ) {\n\t\tvec4 transmittedLight;\n\t\tvec3 transmittance;\n\t\t#ifdef USE_DISPERSION\n\t\t\tfloat halfSpread = ( ior - 1.0 ) * 0.025 * dispersion;\n\t\t\tvec3 iors = vec3( ior - halfSpread, ior, ior + halfSpread );\n\t\t\tfor ( int i = 0; i < 3; i ++ ) {\n\t\t\t\tvec3 transmissionRay = getVolumeTransmissionRay( n, v, thickness, iors[ i ], modelMatrix );\n\t\t\t\tvec3 refractedRayExit = position + transmissionRay;\n\t\t\t\tvec4 ndcPos = projMatrix * viewMatrix * vec4( refractedRayExit, 1.0 );\n\t\t\t\tvec2 refractionCoords = ndcPos.xy / ndcPos.w;\n\t\t\t\trefractionCoords += 1.0;\n\t\t\t\trefractionCoords /= 2.0;\n\t\t\t\tvec4 transmissionSample = getTransmissionSample( refractionCoords, roughness, iors[ i ] );\n\t\t\t\ttransmittedLight[ i ] = transmissionSample[ i ];\n\t\t\t\ttransmittedLight.a += transmissionSample.a;\n\t\t\t\ttransmittance[ i ] = diffuseColor[ i ] * volumeAttenuation( length( transmissionRay ), attenuationColor, attenuationDistance )[ i ];\n\t\t\t}\n\t\t\ttransmittedLight.a /= 3.0;\n\t\t#else\n\t\t\tvec3 transmissionRay = getVolumeTransmissionRay( n, v, thickness, ior, modelMatrix );\n\t\t\tvec3 refractedRayExit = position + transmissionRay;\n\t\t\tvec4 ndcPos = projMatrix * viewMatrix * vec4( refractedRayExit, 1.0 );\n\t\t\tvec2 refractionCoords = ndcPos.xy / ndcPos.w;\n\t\t\trefractionCoords += 1.0;\n\t\t\trefractionCoords /= 2.0;\n\t\