Spherical Harmonics lighting

sh.glsl

// Uniform array of 4 vec3 for SH environment lighting
// Computed from "Ditch River" (http://www.hdrlabs.com/sibl/archive.html)
static const vec3 sphericalHarmonics[4] = {
        {  0.754554516862612,  0.748542953903366,  0.790921515418539 },
        { -0.083856548007422,  0.092533500963210,  0.322764661032516 },
        {  0.308152705331738,  0.366796330467391,  0.466698181299906 },
        { -0.188884931542396, -0.277402551592231, -0.377844212327557 }
};

// Fragment shader, "n" is the normal at the shading point
vec3 Irradiance_SphericalHarmonics(const vec3 n) {
    return max(
          sphericalHarmonics[0]
        + sphericalHarmonics[1] * (n.y)
        + sphericalHarmonics[2] * (n.z)
        + sphericalHarmonics[3] * (n.x)
        , 0.0);
}

// When computing indirect diffuse lighting:
vec3 indirectDiffuse = Irradiance_SphericalHarmonics(n) * Fd_Lambert();