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Merge pull request #101515 from allenwp/agx-negative-optimizations

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Optimize AgX tonemapper's handling of negative values
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Thaddeus Crews 2025-01-20 10:05:38 -06:00
commit 0d4696b472
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2 changed files with 60 additions and 56 deletions
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58
drivers/gles3/shaders/tonemap_inc.glsl
View file

@ -86,7 +86,7 @@ vec3 tonemap_aces(vec3 color, float p_white) {
// Polynomial approximation of EaryChow's AgX sigmoid curve. // Polynomial approximation of EaryChow's AgX sigmoid curve.
// x must be within the range [0.0, 1.0] // x must be within the range [0.0, 1.0]
vec3 agx_default_contrast_approx(vec3 x) { vec3 agx_contrast_approx(vec3 x) {
// Generated with Excel trendline // Generated with Excel trendline
// Input data: Generated using python sigmoid with EaryChow's configuration and 57 steps // Input data: Generated using python sigmoid with EaryChow's configuration and 57 steps
// Additional padding values were added to give correct intersections at 0.0 and 1.0 // Additional padding values were added to give correct intersections at 0.0 and 1.0
@ -96,25 +96,21 @@ vec3 agx_default_contrast_approx(vec3 x) {
return 0.021 * x + 4.0111 * x2 - 25.682 * x2 * x + 70.359 * x4 - 74.778 * x4 * x + 27.069 * x4 * x2; return 0.021 * x + 4.0111 * x2 - 25.682 * x2 * x + 70.359 * x4 - 74.778 * x4 * x + 27.069 * x4 * x2;
} }
const mat3 LINEAR_SRGB_TO_LINEAR_REC2020 = mat3(
vec3(0.6274, 0.0691, 0.0164),
vec3(0.3293, 0.9195, 0.0880),
vec3(0.0433, 0.0113, 0.8956));
// This is an approximation and simplification of EaryChow's AgX implementation that is used by Blender. // This is an approximation and simplification of EaryChow's AgX implementation that is used by Blender.
// This code is based off of the script that generates the AgX_Base_sRGB.cube LUT that Blender uses. // This code is based off of the script that generates the AgX_Base_sRGB.cube LUT that Blender uses.
// Source: https://github.com/EaryChow/AgX_LUT_Gen/blob/main/AgXBasesRGB.py // Source: https://github.com/EaryChow/AgX_LUT_Gen/blob/main/AgXBasesRGB.py
vec3 tonemap_agx(vec3 color) { vec3 tonemap_agx(vec3 color) {
const mat3 agx_inset_matrix = mat3( // Combined linear sRGB to linear Rec 2020 and Blender AgX inset matrices:
0.856627153315983, 0.137318972929847, 0.11189821299995, const mat3 srgb_to_rec2020_agx_inset_matrix = mat3(
0.0951212405381588, 0.761241990602591, 0.0767994186031903, 0.54490813676363087053, 0.14044005884001287035, 0.088827411851915368603,
0.0482516061458583, 0.101439036467562, 0.811302368396859); 0.37377945959812267119, 0.75410959864013760045, 0.17887712465043811023,
0.081384976686407536266, 0.10543358536857773485, 0.73224999956948382528);
// Combined inverse AgX outset matrix and linear Rec 2020 to linear sRGB matrices. // Combined inverse AgX outset matrix and linear Rec 2020 to linear sRGB matrices.
const mat3 agx_outset_rec2020_to_srgb_matrix = mat3( const mat3 agx_outset_rec2020_to_srgb_matrix = mat3(
1.9648846919172409596, -0.29937618452442253746, -0.16440106280678278299, 1.9645509602733325934, -0.29932243390911083839, -0.16436833806080403409,
-0.85594737466675834968, 1.3263980951083531115, -0.23819967517076844919, -0.85585845117807513559, 1.3264510741502356555, -0.23822464068860595117,
-0.10883731725048386702, -0.02702191058393112346, 1.4025007379775505276); -0.10886710826831608324, -0.027084020983874825605, 1.402665347143271889);
// LOG2_MIN = -10.0 // LOG2_MIN = -10.0
// LOG2_MAX = +6.5 // LOG2_MAX = +6.5
@ -122,26 +118,32 @@ vec3 tonemap_agx(vec3 color) {
const float min_ev = -12.4739311883324; // log2(pow(2, LOG2_MIN) * MIDDLE_GRAY) const float min_ev = -12.4739311883324; // log2(pow(2, LOG2_MIN) * MIDDLE_GRAY)
const float max_ev = 4.02606881166759; // log2(pow(2, LOG2_MAX) * MIDDLE_GRAY) const float max_ev = 4.02606881166759; // log2(pow(2, LOG2_MAX) * MIDDLE_GRAY)
// Do AGX in rec2020 to match Blender. // Large negative values in one channel and large positive values in other
color = LINEAR_SRGB_TO_LINEAR_REC2020 * color; // channels can result in a colour that appears darker and more saturated than
// desired after passing it through the inset matrix. For this reason, it is
// best to prevent negative input values.
// This is done before the Rec. 2020 transform to allow the Rec. 2020
// transform to be combined with the AgX inset matrix. This results in a loss
// of color information that could be correctly interpreted within the
// Rec. 2020 color space as positive RGB values, but it is less common for Godot
// to provide this function with negative sRGB values and therefore not worth
// the performance cost of an additional matrix multiplication.
// A value of 2e-10 intentionally introduces insignificant error to prevent
// log2(0.0) after the inset matrix is applied; color will be >= 1e-10 after
// the matrix transform.
color = max(color, 2e-10);
// Preventing negative values is required for the AgX inset matrix to behave correctly. // Do AGX in rec2020 to match Blender and then apply inset matrix.
// This could also be done before the Rec. 2020 transform, allowing the transform to color = srgb_to_rec2020_agx_inset_matrix * color;
// be combined with the AgX inset matrix, but doing this causes a loss of color information
// that could be correctly interpreted within the Rec. 2020 color space.
color = max(color, vec3(0.0));
color = agx_inset_matrix * color;
// Log2 space encoding. // Log2 space encoding.
color = max(color, 1e-10); // Prevent log2(0.0). Possibly unnecessary. // Must be clamped because agx_contrast_approx may not work
// Must be clamped because agx_blender_default_contrast_approx may not work
// well with values outside of the range [0.0, 1.0] // well with values outside of the range [0.0, 1.0]
color = clamp(log2(color), min_ev, max_ev); color = clamp(log2(color), min_ev, max_ev);
color = (color - min_ev) / (max_ev - min_ev); color = (color - min_ev) / (max_ev - min_ev);
// Apply sigmoid function approximation. // Apply sigmoid function approximation.
color = agx_default_contrast_approx(color); color = agx_contrast_approx(color);
// Convert back to linear before applying outset matrix. // Convert back to linear before applying outset matrix.
color = pow(color, vec3(2.4)); color = pow(color, vec3(2.4));
@ -149,9 +151,9 @@ vec3 tonemap_agx(vec3 color) {
// Apply outset to make the result more chroma-laden and then go back to linear sRGB. // Apply outset to make the result more chroma-laden and then go back to linear sRGB.
color = agx_outset_rec2020_to_srgb_matrix * color; color = agx_outset_rec2020_to_srgb_matrix * color;
// Simply hard clip instead of Blender's complex lusRGB.compensate_low_side. // Blender's lusRGB.compensate_low_side is too complex for this shader, so
color = max(color, vec3(0.0)); // simply return the color, even if it has negative components. These negative
// components may be useful for subsequent color adjustments.
return color; return color;
} }

58
servers/rendering/renderer_rd/shaders/effects/tonemap.glsl
View file

@ -266,7 +266,7 @@ vec3 tonemap_aces(vec3 color, float white) {
// Polynomial approximation of EaryChow's AgX sigmoid curve. // Polynomial approximation of EaryChow's AgX sigmoid curve.
// x must be within the range [0.0, 1.0] // x must be within the range [0.0, 1.0]
vec3 agx_default_contrast_approx(vec3 x) { vec3 agx_contrast_approx(vec3 x) {
// Generated with Excel trendline // Generated with Excel trendline
// Input data: Generated using python sigmoid with EaryChow's configuration and 57 steps // Input data: Generated using python sigmoid with EaryChow's configuration and 57 steps
// Additional padding values were added to give correct intersections at 0.0 and 1.0 // Additional padding values were added to give correct intersections at 0.0 and 1.0
@ -276,25 +276,21 @@ vec3 agx_default_contrast_approx(vec3 x) {
return 0.021 * x + 4.0111 * x2 - 25.682 * x2 * x + 70.359 * x4 - 74.778 * x4 * x + 27.069 * x4 * x2; return 0.021 * x + 4.0111 * x2 - 25.682 * x2 * x + 70.359 * x4 - 74.778 * x4 * x + 27.069 * x4 * x2;
} }
const mat3 LINEAR_SRGB_TO_LINEAR_REC2020 = mat3(
vec3(0.6274, 0.0691, 0.0164),
vec3(0.3293, 0.9195, 0.0880),
vec3(0.0433, 0.0113, 0.8956));
// This is an approximation and simplification of EaryChow's AgX implementation that is used by Blender. // This is an approximation and simplification of EaryChow's AgX implementation that is used by Blender.
// This code is based off of the script that generates the AgX_Base_sRGB.cube LUT that Blender uses. // This code is based off of the script that generates the AgX_Base_sRGB.cube LUT that Blender uses.
// Source: https://github.com/EaryChow/AgX_LUT_Gen/blob/main/AgXBasesRGB.py // Source: https://github.com/EaryChow/AgX_LUT_Gen/blob/main/AgXBasesRGB.py
vec3 tonemap_agx(vec3 color) { vec3 tonemap_agx(vec3 color) {
const mat3 agx_inset_matrix = mat3( // Combined linear sRGB to linear Rec 2020 and Blender AgX inset matrices:
0.856627153315983, 0.137318972929847, 0.11189821299995, const mat3 srgb_to_rec2020_agx_inset_matrix = mat3(
0.0951212405381588, 0.761241990602591, 0.0767994186031903, 0.54490813676363087053, 0.14044005884001287035, 0.088827411851915368603,
0.0482516061458583, 0.101439036467562, 0.811302368396859); 0.37377945959812267119, 0.75410959864013760045, 0.17887712465043811023,
0.081384976686407536266, 0.10543358536857773485, 0.73224999956948382528);
// Combined inverse AgX outset matrix and linear Rec 2020 to linear sRGB matrices. // Combined inverse AgX outset matrix and linear Rec 2020 to linear sRGB matrices.
const mat3 agx_outset_rec2020_to_srgb_matrix = mat3( const mat3 agx_outset_rec2020_to_srgb_matrix = mat3(
1.9648846919172409596, -0.29937618452442253746, -0.16440106280678278299, 1.9645509602733325934, -0.29932243390911083839, -0.16436833806080403409,
-0.85594737466675834968, 1.3263980951083531115, -0.23819967517076844919, -0.85585845117807513559, 1.3264510741502356555, -0.23822464068860595117,
-0.10883731725048386702, -0.02702191058393112346, 1.4025007379775505276); -0.10886710826831608324, -0.027084020983874825605, 1.402665347143271889);
// LOG2_MIN = -10.0 // LOG2_MIN = -10.0
// LOG2_MAX = +6.5 // LOG2_MAX = +6.5
@ -302,26 +298,32 @@ vec3 tonemap_agx(vec3 color) {
const float min_ev = -12.4739311883324; // log2(pow(2, LOG2_MIN) * MIDDLE_GRAY) const float min_ev = -12.4739311883324; // log2(pow(2, LOG2_MIN) * MIDDLE_GRAY)
const float max_ev = 4.02606881166759; // log2(pow(2, LOG2_MAX) * MIDDLE_GRAY) const float max_ev = 4.02606881166759; // log2(pow(2, LOG2_MAX) * MIDDLE_GRAY)
// Do AGX in rec2020 to match Blender. // Large negative values in one channel and large positive values in other
color = LINEAR_SRGB_TO_LINEAR_REC2020 * color; // channels can result in a colour that appears darker and more saturated than
// desired after passing it through the inset matrix. For this reason, it is
// best to prevent negative input values.
// This is done before the Rec. 2020 transform to allow the Rec. 2020
// transform to be combined with the AgX inset matrix. This results in a loss
// of color information that could be correctly interpreted within the
// Rec. 2020 color space as positive RGB values, but it is less common for Godot
// to provide this function with negative sRGB values and therefore not worth
// the performance cost of an additional matrix multiplication.
// A value of 2e-10 intentionally introduces insignificant error to prevent
// log2(0.0) after the inset matrix is applied; color will be >= 1e-10 after
// the matrix transform.
color = max(color, 2e-10);
// Preventing negative values is required for the AgX inset matrix to behave correctly. // Do AGX in rec2020 to match Blender and then apply inset matrix.
// This could also be done before the Rec. 2020 transform, allowing the transform to color = srgb_to_rec2020_agx_inset_matrix * color;
// be combined with the AgX inset matrix, but doing this causes a loss of color information
// that could be correctly interpreted within the Rec. 2020 color space.
color = max(color, vec3(0.0));
color = agx_inset_matrix * color;
// Log2 space encoding. // Log2 space encoding.
color = max(color, 1e-10); // Prevent log2(0.0). Possibly unnecessary. // Must be clamped because agx_contrast_approx may not work
// Must be clamped because agx_blender_default_contrast_approx may not work
// well with values outside of the range [0.0, 1.0] // well with values outside of the range [0.0, 1.0]
color = clamp(log2(color), min_ev, max_ev); color = clamp(log2(color), min_ev, max_ev);
color = (color - min_ev) / (max_ev - min_ev); color = (color - min_ev) / (max_ev - min_ev);
// Apply sigmoid function approximation. // Apply sigmoid function approximation.
color = agx_default_contrast_approx(color); color = agx_contrast_approx(color);
// Convert back to linear before applying outset matrix. // Convert back to linear before applying outset matrix.
color = pow(color, vec3(2.4)); color = pow(color, vec3(2.4));
@ -329,9 +331,9 @@ vec3 tonemap_agx(vec3 color) {
// Apply outset to make the result more chroma-laden and then go back to linear sRGB. // Apply outset to make the result more chroma-laden and then go back to linear sRGB.
color = agx_outset_rec2020_to_srgb_matrix * color; color = agx_outset_rec2020_to_srgb_matrix * color;
// Simply hard clip instead of Blender's complex lusRGB.compensate_low_side. // Blender's lusRGB.compensate_low_side is too complex for this shader, so
color = max(color, vec3(0.0)); // simply return the color, even if it has negative components. These negative
// components may be useful for subsequent color adjustments.
return color; return color;
} }