59 lines
1.6 KiB
GLSL
59 lines
1.6 KiB
GLSL
/*******************************************************************************************
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*
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* rPBR [shader] - Irradiance cubemap fragment shader
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*
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* Copyright (c) 2017 Victor Fisac
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*
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**********************************************************************************************/
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#version 330
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// Input vertex attributes (from vertex shader)
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in vec3 fragPosition;
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// Input uniform values
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uniform samplerCube environmentMap;
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// Constant values
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const float PI = 3.14159265359;
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// Output fragment color
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out vec4 finalColor;
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void main()
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{
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// The sample direction equals the hemisphere's orientation
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vec3 normal = normalize(fragPosition);
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vec3 irradiance = vec3(0.0);
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vec3 up = vec3(0.0, 1.0, 0.0);
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vec3 right = cross(up, normal);
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up = cross(normal, right);
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float sampleDelta = 0.025;
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float nrSamples = 0.0;
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for (float phi = 0.0; phi < 2.0*PI; phi += sampleDelta)
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{
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for (float theta = 0.0; theta < 0.5*PI; theta += sampleDelta)
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{
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// Spherical to cartesian (in tangent space)
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vec3 tangentSample = vec3(sin(theta)*cos(phi), sin(theta)*sin(phi), cos(theta));
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// tangent space to world
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vec3 sampleVec = tangentSample.x*right + tangentSample.y*up + tangentSample.z*normal;
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// Fetch color from environment cubemap
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irradiance += texture(environmentMap, sampleVec).rgb*cos(theta)*sin(theta);
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nrSamples++;
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}
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}
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// Calculate irradiance average value from samples
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irradiance = PI*irradiance*(1.0/float(nrSamples));
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// Calculate final fragment color
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finalColor = vec4(irradiance, 1.0);
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}
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