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