64 lines
1.8 KiB
C
64 lines
1.8 KiB
C
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#pragma once
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#include <glm/ext.hpp>
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#include <glm/glm.hpp>
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enum ToneMappingMode {
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ToneMapping_None = 0,
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ToneMapping_Reinhard = 1,
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ToneMapping_Uchimura = 2,
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ToneMapping_KhronosPBR = 3,
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};
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// Uchimura 2017, "HDR theory and practice"
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// Math: https://www.desmos.com/calculator/gslcdxvipg
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// Source: https://www.slideshare.net/nikuque/hdr-theory-and-practicce-jp
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float uchimura(float x, float P, float a, float m, float l, float c, float b)
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{
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float l0 = ((P - m) * l) / a;
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float L0 = m - m / a;
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float L1 = m + (1.0f - m) / a;
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float S0 = m + l0;
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float S1 = m + a * l0;
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float C2 = (a * P) / (P - S1);
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float CP = -C2 / P;
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float w0 = float(1.0f - glm::smoothstep(0.0f, m, x));
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float w2 = float(glm::step(m + l0, x));
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float w1 = float(1.0f - w0 - w2);
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float T = float(m * pow(x / m, float(c)) + b);
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float S = float(P - (P - S1) * exp(CP * (x - S0)));
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float L = float(m + a * (x - m));
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return T * w0 + L * w1 + S * w2;
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}
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float reinhard2(float v, float maxWhite)
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{
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return v * (1.0f + (v / (maxWhite * maxWhite))) / (1.0f + v);
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}
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// Khronos PBR Neutral Tone Mapper
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// https://github.com/KhronosGroup/ToneMapping/blob/main/PBR_Neutral/README.md#pbr-neutral-specification
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// https://github.com/KhronosGroup/ToneMapping/blob/main/PBR_Neutral/pbrNeutral.glsl
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float PBRNeutralToneMapping(float color, float startCompression, float desaturation)
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{
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startCompression -= 0.04f;
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float x = color;
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float offset = x < 0.08f ? x - 6.25f * x * x : 0.04f;
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color -= offset;
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float peak = color;
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if (peak < startCompression)
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return color;
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const float d = 1. - startCompression;
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float newPeak = 1. - d * d / (peak + d - startCompression);
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color *= newPeak / peak;
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float g = 1.0f - 1.0f / (desaturation * (peak - newPeak) + 1.0f);
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return glm::mix(color, newPeak, g);
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}
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