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Switch white balance to CAT16 and add gamut mapping code (#4457)

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This commit is contained in:
Romain Guy
2021-08-05 12:44:49 -07:00
committed by GitHub
parent 4e33e9c3d1
commit f804c9e346
6 changed files with 348 additions and 28 deletions
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2
filament/CMakeLists.txt
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@@ -51,6 +51,7 @@ set(SRCS
src/Camera.cpp
src/Color.cpp
src/ColorGrading.cpp
src/ColorSpace.cpp
src/Culler.cpp
src/DFG.cpp
src/DebugRegistry.cpp
@@ -100,6 +101,7 @@ set(SRCS
)
set(PRIVATE_HDRS
src/ColorSpace.h
src/FilamentAPI-impl.h
src/FrameHistory.h
src/FrameInfo.h

21
filament/src/ColorGrading.cpp
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@@ -265,7 +265,7 @@ inline float3 adjustExposure(float3 v, float exposure) {
// Return the chromatic adaptation coefficients in LMS space for the given
// temperature/tint offsets. The chromatic adaption is perfomed following
// the von Kries method, using the CIECAT02 transform.
// the von Kries method, using the CIECAT16 transform.
// See https://en.wikipedia.org/wiki/Chromatic_adaptation
// See https://en.wikipedia.org/wiki/CIECAM02#Chromatic_adaptation
UTILS_ALWAYS_INLINE
@@ -277,13 +277,13 @@ inline float3 adaptationTransform(float2 whiteBalance) {
float x = ILLUMINANT_D65_xyY.x - k * (k < 0.0f ? 0.0214f : 0.066f);
float y = chromaticityCoordinateIlluminantD(x) + t * 0.066f;
float3 lms = XYZ_to_CIECAT02 * xyY_to_XYZ({x, y, 1.0f});
return ILLUMINANT_D65_LMS / lms;
float3 lms = XYZ_to_CIECAT16 * xyY_to_XYZ({x, y, 1.0f});
return ILLUMINANT_D65_LMS_CAT16 / lms;
}
UTILS_ALWAYS_INLINE
inline float3 chromaticAdaptation(float3 v, float3 adaptationTransform) {
return LMS_to_sRGB * (adaptationTransform * (sRGB_to_LMS * v));
return LMS_CAT16_to_sRGB * (adaptationTransform * (sRGB_to_LMS_CAT16 * v));
}
//------------------------------------------------------------------------------
@@ -381,7 +381,7 @@ static float3 luminanceScaling(float3 x,
float luminanceIn = dot(x, luminanceWeights);
// TODO: We could optimize for the case of single-channel luminance
float luminanceOut = toneMapper(luminanceIn).x;
float luminanceOut = toneMapper(luminanceIn).y;
float peak = max(x);
float3 chromaRatio = max(x / peak, 0.0f);
@@ -512,6 +512,7 @@ FColorGrading::FColorGrading(FEngine& engine, const Builder& builder) {
v = LogC_to_linear(v);
// TODO: Performed in sRGB, should be in Rec.2020 or AP1
if (builder->hasAdjustments) {
// Exposure
v = adjustExposure(v, builder->exposure);
@@ -570,7 +571,9 @@ FColorGrading::FColorGrading(FEngine& engine, const Builder& builder) {
// TODO: We should convert to the output color space if we use a working
// color space that's not sRGB
// TODO: Allow the user to customize the output color space
// TODO: Gamut mapping
// We need to clamp for the output transfer function
v = saturate(v);
// Apply OECF
@@ -591,10 +594,10 @@ FColorGrading::FColorGrading(FEngine& engine, const Builder& builder) {
#pragma clang loop vectorize_width(8)
for (size_t i = 0; i < count; ++i) {
float4 v{src[i]};
uint32_t r = uint32_t(std::floor(v.x * 1023.0f + 0.5f));
uint32_t g = uint32_t(std::floor(v.y * 1023.0f + 0.5f));
uint32_t b = uint32_t(std::floor(v.z * 1023.0f + 0.5f));
dst[i] = (b << 20u) | (g << 10u) | r;
uint32_t pr = uint32_t(std::floor(v.x * 1023.0f + 0.5f));
uint32_t pg = uint32_t(std::floor(v.y * 1023.0f + 0.5f));
uint32_t pb = uint32_t(std::floor(v.z * 1023.0f + 0.5f));
dst[i] = (pb << 20u) | (pg << 10u) | pr;
}
}

266
filament/src/ColorSpace.cpp Normal file
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@@ -0,0 +1,266 @@
/*
* Copyright (C) 2021 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "ColorSpace.h"
namespace filament {
using namespace math;
/*
* The section below is subject to the following license.
* Source: https://bottosson.github.io/posts/gamutclipping/
*
* Copyright (c) 2021 Björn Ottosson
*
* Permission is hereby granted, free of charge, to any person obtaining a copy of
* this software and associated documentation files (the "Software"), to deal in
* the Software without restriction, including without limitation the rights to
* use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
* of the Software, and to permit persons to whom the Software is furnished to do
* so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/
// Finds the maximum saturation possible for a given hue that fits in sRGB
// Saturation here is defined as S = C/L
// a and b must be normalized so a^2 + b^2 == 1
float compute_max_saturation(float a, float b) noexcept {
// Max saturation will be when one of r, g or b goes below zero.
// Select different coefficients depending on which component goes below zero first
float k0, k1, k2, k3, k4, wl, wm, ws;
if (-1.88170328f * a - 0.80936493f * b > 1) {
// Red component
k0 = +1.19086277f;
k1 = +1.76576728f;
k2 = +0.59662641f;
k3 = +0.75515197f;
k4 = +0.56771245f;
wl = +4.0767416621f;
wm = -3.3077115913f;
ws = +0.2309699292f;
} else if (1.81444104f * a - 1.19445276f * b > 1) {
// Green component
k0 = +0.73956515f;
k1 = -0.45954404f;
k2 = +0.08285427f;
k3 = +0.12541070f;
k4 = +0.14503204f;
wl = -1.2681437731f;
wm = +2.6097574011f;
ws = -0.3413193965f;
} else {
// Blue component
k0 = +1.35733652f;
k1 = -0.00915799f;
k2 = -1.15130210f;
k3 = -0.50559606f;
k4 = +0.00692167f;
wl = -0.0041960863f;
wm = -0.7034186147f;
ws = +1.7076147010f;
}
// Approximate max saturation using a polynomial:
float S = k0 + k1 * a + k2 * b + k3 * a * a + k4 * a * b;
// Do one step Halley's method to get closer
// this gives an error less than 10e6, except for some blue hues where the dS/dh
// is close to infinite
// this should be sufficient for most applications, otherwise do two/three steps
float k_l = +0.3963377774f * a + 0.2158037573f * b;
float k_m = -0.1055613458f * a - 0.0638541728f * b;
float k_s = -0.0894841775f * a - 1.2914855480f * b;
{
float l_ = 1.f + S * k_l;
float m_ = 1.f + S * k_m;
float s_ = 1.f + S * k_s;
float l = l_ * l_ * l_;
float m = m_ * m_ * m_;
float s = s_ * s_ * s_;
float l_dS = 3.f * k_l * l_ * l_;
float m_dS = 3.f * k_m * m_ * m_;
float s_dS = 3.f * k_s * s_ * s_;
float l_dS2 = 6.f * k_l * k_l * l_;
float m_dS2 = 6.f * k_m * k_m * m_;
float s_dS2 = 6.f * k_s * k_s * s_;
float f = wl * l + wm * m + ws * s;
float f1 = wl * l_dS + wm * m_dS + ws * s_dS;
float f2 = wl * l_dS2 + wm * m_dS2 + ws * s_dS2;
S = S - f * f1 / (f1 * f1 - 0.5f * f * f2);
}
return S;
}
// finds L_cusp and C_cusp for a given hue
// a and b must be normalized so a^2 + b^2 == 1
float2 find_cusp(float a, float b) noexcept {
// First, find the maximum saturation (saturation S = C/L)
float S_cusp = compute_max_saturation(a, b);
// Convert to linear sRGB to find the first point where at least one of r,g or b >= 1:
float3 rgb_at_max = OkLab_to_sRGB({1.0f, S_cusp * a, S_cusp * b});
float L_cusp = std::cbrt(1.f / max(max(rgb_at_max.r, rgb_at_max.g), rgb_at_max.b));
float C_cusp = L_cusp * S_cusp;
return {L_cusp, C_cusp};
}
// Finds intersection of the line defined by
// L = L0 * (1 - t) + t * L1;
// C = t * C1;
// a and b must be normalized so a^2 + b^2 == 1
float find_gamut_intersection(float a, float b, float L1, float C1, float L0) noexcept {
// Find the cusp of the gamut triangle
float2 cusp = find_cusp(a, b);
// Find the intersection for upper and lower half seprately
float t;
if (((L1 - L0) * cusp.y - (cusp.x - L0) * C1) <= 0.f) {
// Lower half
t = cusp.y * L0 / (C1 * cusp.x + cusp.y * (L0 - L1));
} else {
// Upper half
// First intersect with triangle
t = cusp.y * (L0 - 1.f) / (C1 * (cusp.x - 1.f) + cusp.y * (L0 - L1));
// Then one step Halley's method
{
float dL = L1 - L0;
float dC = C1;
float k_l = +0.3963377774f * a + 0.2158037573f * b;
float k_m = -0.1055613458f * a - 0.0638541728f * b;
float k_s = -0.0894841775f * a - 1.2914855480f * b;
float l_dt = dL + dC * k_l;
float m_dt = dL + dC * k_m;
float s_dt = dL + dC * k_s;
// If higher accuracy is required, 2 or 3 iterations of the
// following block can be used:
{
float L = L0 * (1.f - t) + t * L1;
float C = t * C1;
float l_ = L + C * k_l;
float m_ = L + C * k_m;
float s_ = L + C * k_s;
float l = l_ * l_ * l_;
float m = m_ * m_ * m_;
float s = s_ * s_ * s_;
float ldt = 3 * l_dt * l_ * l_;
float mdt = 3 * m_dt * m_ * m_;
float sdt = 3 * s_dt * s_ * s_;
float ldt2 = 6 * l_dt * l_dt * l_;
float mdt2 = 6 * m_dt * m_dt * m_;
float sdt2 = 6 * s_dt * s_dt * s_;
float r = 4.0767416621f * l - 3.3077115913f * m + 0.2309699292f * s - 1;
float r1 = 4.0767416621f * ldt - 3.3077115913f * mdt + 0.2309699292f * sdt;
float r2 = 4.0767416621f * ldt2 - 3.3077115913f * mdt2 + 0.2309699292f * sdt2;
float u_r = r1 / (r1 * r1 - 0.5f * r * r2);
float t_r = -r * u_r;
float g = -1.2681437731f * l + 2.6097574011f * m - 0.3413193965f * s - 1;
float g1 = -1.2681437731f * ldt + 2.6097574011f * mdt - 0.3413193965f * sdt;
float g2 = -1.2681437731f * ldt2 + 2.6097574011f * mdt2 - 0.3413193965f * sdt2;
float u_g = g1 / (g1 * g1 - 0.5f * g * g2);
float t_g = -g * u_g;
float b0 = -0.0041960863f * l - 0.7034186147f * m + 1.7076147010f * s - 1;
float b1 = -0.0041960863f * ldt - 0.7034186147f * mdt + 1.7076147010f * sdt;
float b2 = -0.0041960863f * ldt2 - 0.7034186147f * mdt2 + 1.7076147010f * sdt2;
float u_b = b1 / (b1 * b1 - 0.5f * b0 * b2);
float t_b = -b0 * u_b;
t_r = u_r >= 0.f ? t_r : std::numeric_limits<float>::max();
t_g = u_g >= 0.f ? t_g : std::numeric_limits<float>::max();
t_b = u_b >= 0.f ? t_b : std::numeric_limits<float>::max();
t += min(t_r, min(t_g, t_b));
}
}
}
return t;
}
constexpr float sgn(float x) noexcept {
return (float) (0.f < x) - (float) (x < 0.f);
}
inline float3 gamut_clip_adaptive_L0_0_5(float3 rgb, float alpha = 0.05f) noexcept {
if (all(lessThanEqual(rgb, float3{1.0f})) && all(greaterThanEqual(rgb, float3{0.0f}))) {
return rgb;
}
float3 lab = sRGB_to_OkLab(rgb);
float L = lab.x;
float eps = 0.00001f;
float C = max(eps, std::sqrt(lab.y * lab.y + lab.z * lab.z));
float a_ = lab.y / C;
float b_ = lab.z / C;
float Ld = L - 0.5f;
float e1 = 0.5f + std::abs(Ld) + alpha * C;
float L0 = 0.5f * (1.f + sgn(Ld) * (e1 - std::sqrt(e1 * e1 - 2.f * std::abs(Ld))));
float t = find_gamut_intersection(a_, b_, L, C, L0);
float L_clipped = L0 * (1.f - t) + t * L;
float C_clipped = t * C;
return OkLab_to_sRGB({L_clipped, C_clipped * a_, C_clipped * b_});
}
float3 gamutMapping_sRGB(float3 rgb) noexcept {
return gamut_clip_adaptive_L0_0_5(rgb, 0.5f);
}
/*
* End source: https://bottosson.github.io/posts/gamutclipping/
*/
} //namespace filament

74
filament/src/ColorSpace.h
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@@ -64,16 +64,16 @@ constexpr mat3f XYZ_to_REC2020{
-0.2533663f, 0.0157685f, 0.9421031f
};
constexpr mat3f XYZ_to_CIECAT02{
0.7328000f, -0.7036000f, 0.0030000f,
0.4296000f, 1.6975000f, 0.0136000f,
-0.1624000f, 0.0061000f, 0.9834000f
constexpr mat3f XYZ_to_CIECAT16{
0.401288f, -0.250268f, -0.002079f,
0.650173f, 1.204414f, 0.048952f,
-0.051461f, 0.045854f, 0.953127f
};
constexpr mat3f CIECAT02_to_XYZ{
1.0961200f, 0.4543690f, -0.0096276f,
-0.2788690f, 0.4735330f, -0.0056980f,
0.1827450f, 0.0720978f, 1.0153300f
constexpr mat3f CIECAT16_to_XYZ{
1.862068f, 0.387527f, -0.015841f,
-1.011255f, 0.621447f, -0.034123f,
0.149187f, -0.008974f, 1.049964f
};
constexpr mat3f AP1_to_XYZ{
@@ -119,18 +119,42 @@ constexpr mat3f AP0_to_sRGB{
};
constexpr mat3f sRGB_to_AP0{
0.4397010f, 0.0897923f, 0.0175440f,
0.3829780f, 0.8134230f, 0.1115440f,
0.1773350f, 0.0967616f, 0.8707040f
0.4397010f, 0.0897923f, 0.0175440f,
0.3829780f, 0.8134230f, 0.1115440f,
0.1773350f, 0.0967616f, 0.8707040f
};
constexpr mat3f sRGB_to_OkLab_LMS{
0.4122214708f, 0.2119034982f, 0.0883024619f,
0.5363325363f, 0.6806995451f, 0.2817188376f,
0.0514459929f, 0.1073969566f, 0.6299787005f
};
constexpr mat3f OkLab_LMS_to_OkLab{
0.2104542553f, 1.9779984951f, 0.0259040371f,
0.7936177850f, -2.4285922050f, 0.7827717662f,
-0.0040720468f, 0.4505937099f, -0.8086757660f
};
constexpr mat3f OkLab_to_OkLab_LMS{
1.0000000000f, 1.0000000000f, 1.0000000000f,
0.3963377774f, -0.1055613458f, -0.0894841775f,
0.2158037573f, -0.0638541728f, -1.2914855480f
};
constexpr mat3f OkLab_LMS_to_sRGB{
4.0767416621f, -1.2684380046f, -0.0041960863f,
-3.3077115913f, 2.6097574011f, -0.7034186147f,
0.2309699292f, -0.3413193965f, 1.7076147010f
};
constexpr mat3f sRGB_to_REC2020 = XYZ_to_REC2020 * sRGB_to_XYZ;
constexpr mat3f REC2020_to_sRGB = XYZ_to_sRGB * REC2020_to_XYZ;
constexpr mat3f sRGB_to_LMS = XYZ_to_CIECAT02 * sRGB_to_XYZ;
constexpr mat3f sRGB_to_LMS_CAT16 = XYZ_to_CIECAT16 * sRGB_to_XYZ;
constexpr mat3f LMS_to_sRGB = XYZ_to_sRGB * CIECAT02_to_XYZ;
constexpr mat3f LMS_CAT16_to_sRGB = XYZ_to_sRGB * CIECAT16_to_XYZ;
constexpr mat3f REC2020_to_AP0 = AP1_to_AP0 * XYZ_to_AP1 * REC2020_to_XYZ;
@@ -143,9 +167,9 @@ constexpr mat3f AP1_to_REC2020 = XYZ_to_REC2020 * AP1_to_XYZ;
// Standard CIE 1931 2° illuminant D65, in xyY space
constexpr float3 ILLUMINANT_D65_xyY{0.31271f, 0.32902f, 1.0f};
// Standard CIE 1931 2° illuminant D65, in LMS space (CIECAT02)
// Result of: XYZ_to_CIECAT02 * xyY_to_XYZ(ILLUMINANT_D65_xyY);
constexpr float3 ILLUMINANT_D65_LMS{0.949237f, 1.03542f, 1.08728f};
// Standard CIE 1931 2° illuminant D65, in LMS space (CIECAT16)
// Result of: XYZ_to_CIECAT16 * xyY_to_XYZ(ILLUMINANT_D65_xyY);
constexpr float3 ILLUMINANT_D65_LMS_CAT16{0.975533f, 1.016483f, 1.084837f};
// RGB to luminance coefficients for Rec.2020, from REC2020_to_XYZ
constexpr float3 LUMA_REC2020{0.2627002f, 0.6779981f, 0.0593017f};
@@ -187,6 +211,18 @@ inline constexpr xyY XYZ_to_xyY(XYZ v) noexcept {
return float3(v.xy / max(v.x + v.y + v.z, 1e-5f), v.y);
}
inline float3 sRGB_to_OkLab(float3 x) noexcept {
return OkLab_LMS_to_OkLab * cbrt(sRGB_to_OkLab_LMS * x);
}
inline constexpr float3 pow3(float3 x) noexcept {
return x * x * x;
}
inline float3 OkLab_to_sRGB(float3 x) noexcept {
return OkLab_LMS_to_sRGB * pow3(OkLab_to_OkLab_LMS * x);
}
//------------------------------------------------------------------------------
// Conversion functions and encoding/decoding
//------------------------------------------------------------------------------
@@ -284,6 +320,12 @@ inline float3 EOCF_PQ(float3 x, float maxPqValue) {
return linearColor * maxPqValue;
}
//------------------------------------------------------------------------------
// Gamut mapping
//------------------------------------------------------------------------------
float3 gamutMapping_sRGB(float3 rgb) noexcept;
} // namespace filament
#endif //TNT_FILAMENT_COLOR_SPACE_H

7
libs/math/include/math/TVecHelpers.h
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@@ -463,6 +463,13 @@ private:
return v;
}
friend inline VECTOR<T> MATH_PURE cbrt(VECTOR<T> v) {
for (size_t i = 0; i < v.size(); i++) {
v[i] = std::cbrt(v[i]);
}
return v;
}
friend inline VECTOR<T> MATH_PURE exp(VECTOR<T> v) {
for (size_t i = 0; i < v.size(); i++) {
v[i] = std::exp(v[i]);

6
libs/viewer/src/SimpleViewer.cpp
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@@ -379,9 +379,9 @@ SimpleViewer::SimpleViewer(filament::Engine* engine, filament::Scene* scene, fil
.intensity(mSettings.lighting.sunlightIntensity)
.direction(normalize(mSettings.lighting.sunlightDirection))
.castShadows(true)
.sunAngularRadius(1.9)
.sunHaloSize(10.0)
.sunHaloFalloff(80.0)
.sunAngularRadius(1.0f)
.sunHaloSize(2.0f)
.sunHaloFalloff(80.0f)
.build(*engine, mSunlight);
if (mSettings.lighting.enableSunlight) {
mScene->addEntity(mSunlight);