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| ** Copyright (C) 2014 NVIDIA Corporation. |
| ** Copyright (C) 2019 The Qt Company Ltd. |
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| |
| vec3 evalEnvironmentMap( in vec3 R, float roughness ) |
| { |
| // convert R to spherical texture coordinates |
| vec2 tc = vec2( ( atan( R.x, -R.z ) + PI ) / ( PI_TWO ), acos( -R.y ) / PI ); |
| |
| vec2 envMapSize = vec2( textureSize( uEnvironmentTexture, 0 ) ); |
| float envMapLevels = log2( max( envMapSize.x, envMapSize.y ) ); |
| |
| // simulate textureQueryLod |
| vec2 dx = dFdx( tc * envMapSize.x ); |
| vec2 dy = dFdy( tc * envMapSize.y ); |
| |
| float px = dot( dx, dx ); |
| float py = dot( dy, dy ); |
| |
| float maxlod = 0.5 * log2( max( px, py ) ); // log2(sqrt()) = 0.5*log2() |
| float minlod = 0.5 * log2( min( px, py ) ); |
| |
| //float lod = max(0.0, maxlod - min( maxlod - minlod, envMapLevels )); |
| float lod = max(0.0, min( minlod, envMapLevels )); |
| |
| float roughLevel = mix( lod , envMapLevels, roughness ); |
| |
| return( textureLod( uEnvironmentTexture, tc, roughLevel ).rgb ); |
| } |