58 lines
1.7 KiB
GLSL
58 lines
1.7 KiB
GLSL
#ifndef IBL_COMMON_GLSL
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#define IBL_COMMON_GLSL
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// IBL bindings (set=3): specular equirect 2D, BRDF LUT, SH UBO.
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layout(set=3, binding=0) uniform sampler2D iblSpec2D;
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layout(set=3, binding=1) uniform sampler2D iblBRDF;
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layout(std140, set=3, binding=2) uniform IBL_SH { vec4 sh[9]; } iblSH;
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// Evaluate diffuse irradiance from 2nd-order SH coefficients (9 coeffs).
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// Coefficients are pre-convolved with the Lambert kernel on the CPU.
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vec3 sh_eval_irradiance(vec3 n)
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{
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float x = n.x, y = n.y, z = n.z;
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const float c0 = 0.2820947918;
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const float c1 = 0.4886025119;
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const float c2 = 1.0925484306;
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const float c3 = 0.3153915653;
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const float c4 = 0.5462742153;
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float Y[9];
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Y[0] = c0;
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Y[1] = c1 * y;
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Y[2] = c1 * z;
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Y[3] = c1 * x;
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Y[4] = c2 * x * y;
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Y[5] = c2 * y * z;
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Y[6] = c3 * (3.0 * z * z - 1.0);
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Y[7] = c2 * x * z;
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Y[8] = c4 * (x * x - y * y);
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vec3 r = vec3(0.0);
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for (int i = 0; i < 9; ++i)
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{
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r += iblSH.sh[i].rgb * Y[i];
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}
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return r;
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}
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// Map direction to equirectangular UV (same convention across shaders).
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vec2 dir_to_equirect(vec3 d)
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{
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d = normalize(d);
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float phi = atan(d.z, d.x);
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float theta = acos(clamp(d.y, -1.0, 1.0));
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// 1/(2*pi) = 0.15915494309, 1/pi = 0.31830988618
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return vec2(phi * 0.15915494309 + 0.5, theta * 0.31830988618);
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}
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// Helper for selecting mip LOD from roughness and available levels.
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// Uses roughness^2 to bias towards blurrier reflections at mid roughness.
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float ibl_lod_from_roughness(float roughness, float levels)
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{
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float maxLevel = max(levels - 1.0, 0.0);
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float r = clamp(roughness, 0.0, 1.0);
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return r * r * maxLevel;
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}
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#endif // IBL_COMMON_GLSL
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