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uniform float maxLuminance;
uniform float dstMaxLuminance;
uniform float dstRefLuminance;
const mat3 BT2020toLMS = mat3(
0.3592, 0.6976, -0.0358,
-0.1922, 1.1004, 0.0755,
0.0070, 0.0749, 0.8434
);
//const mat3 LMStoBT2020 = inverse(BT2020toLMS);
const mat3 LMStoBT2020 = mat3(
2.0701800566956135096, -1.3264568761030210255, 0.20661600684785517081,
0.36498825003265747974, 0.68046736285223514102, -0.045421753075853231409,
-0.049595542238932107896, -0.049421161186757487412, 1.1879959417328034394
);
// const mat3 ICtCpPQ = transpose(mat3(
// 2048.0, 2048.0, 0.0,
// 6610.0, -13613.0, 7003.0,
// 17933.0, -17390.0, -543.0
// ) / 4096.0);
const mat3 ICtCpPQ = mat3(
0.5, 1.61376953125, 4.378173828125,
0.5, -3.323486328125, -4.24560546875,
0.0, 1.709716796875, -0.132568359375
);
//const mat3 ICtCpPQInv = inverse(ICtCpPQ);
const mat3 ICtCpPQInv = mat3(
1.0, 1.0, 1.0,
0.0086090370379327566, -0.0086090370379327566, 0.560031335710679118,
0.11102962500302595656, -0.11102962500302595656, -0.32062717498731885185
);
// unused for now
// const mat3 ICtCpHLG = transpose(mat3(
// 2048.0, 2048.0, 0.0,
// 3625.0, -7465.0, 3840.0,
// 9500.0, -9212.0, -288.0
// ) / 4096.0);
// const mat3 ICtCpHLGInv = inverse(ICtCpHLG);
vec4 tonemap(vec4 color, mat3 dstXYZ) {
if (maxLuminance < dstMaxLuminance * 1.01)
return vec4(clamp(color.rgb, vec3(0.0), vec3(dstMaxLuminance)), color[3]);
mat3 toLMS = BT2020toLMS * dstXYZ;
mat3 fromLMS = inverse(dstXYZ) * LMStoBT2020;
vec3 lms = fromLinear(vec4((toLMS * color.rgb) / HDR_MAX_LUMINANCE, 1.0), CM_TRANSFER_FUNCTION_ST2084_PQ).rgb;
vec3 ICtCp = ICtCpPQ * lms;
float E = pow(clamp(ICtCp[0], 0.0, 1.0), PQ_INV_M2);
float luminance = pow(
(max(E - PQ_C1, 0.0)) / (PQ_C2 - PQ_C3 * E),
PQ_INV_M1
) * HDR_MAX_LUMINANCE;
float linearPart = min(luminance, dstRefLuminance);
float luminanceAboveRef = max(luminance - dstRefLuminance, 0.0);
float maxExcessLuminance = max(maxLuminance - dstRefLuminance, 1.0);
float shoulder = log((luminanceAboveRef / maxExcessLuminance + 1.0) * (M_E - 1.0));
float mappedHigh = shoulder * (dstMaxLuminance - dstRefLuminance);
float newLum = clamp(linearPart + mappedHigh, 0.0, dstMaxLuminance);
// scale src to dst reference
float refScale = dstRefLuminance / srcRefLuminance;
return vec4(fromLMS * toLinear(vec4(ICtCpPQInv * ICtCp, 1.0), CM_TRANSFER_FUNCTION_ST2084_PQ).rgb * HDR_MAX_LUMINANCE * refScale, color[3]);
}
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