diff --git a/drivers/gles3/shaders/tonemap_inc.glsl b/drivers/gles3/shaders/tonemap_inc.glsl index 2219c39f753e..b695332500e8 100644 --- a/drivers/gles3/shaders/tonemap_inc.glsl +++ b/drivers/gles3/shaders/tonemap_inc.glsl @@ -84,71 +84,73 @@ vec3 tonemap_aces(vec3 color, float p_white) { return color_tonemapped / p_white_tonemapped; } -// Mean error^2: 3.6705141e-06 +// Polynomial approximation of EaryChow's AgX sigmoid curve. +// In Blender's implementation, numbers could go a little bit over 1.0, so it's best to ensure +// this behaves the same as Blender's with values up to 1.1. Input values cannot be lower than 0. vec3 agx_default_contrast_approx(vec3 x) { + // Generated with Excel trendline + // Input data: Generated using python sigmoid with EaryChow's configuration and 57 steps + // 6th order, intercept of 0.0 to remove an operation and ensure intersection at 0.0 vec3 x2 = x * x; vec3 x4 = x2 * x2; - - return +15.5 * x4 * x2 - 40.14 * x4 * x + 31.96 * x4 - 6.868 * x2 * x + 0.4298 * x2 + 0.1191 * x - 0.00232; + return -0.20687445 * x + 6.80888933 * x2 - 37.60519607 * x2 * x + 93.32681938 * x4 - 95.2780858 * x4 * x + 33.96372259 * x4 * x2; } -const mat3 LINEAR_REC2020_TO_LINEAR_SRGB = mat3( - vec3(1.6605, -0.1246, -0.0182), - vec3(-0.5876, 1.1329, -0.1006), - vec3(-0.0728, -0.0083, 1.1187)); - 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)); -vec3 agx(vec3 val) { - const mat3 agx_mat = mat3( +// 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. +// Source: https://github.com/EaryChow/AgX_LUT_Gen/blob/main/AgXBasesRGB.py +vec3 tonemap_agx(vec3 color) { + const mat3 agx_inset_matrix = mat3( 0.856627153315983, 0.137318972929847, 0.11189821299995, 0.0951212405381588, 0.761241990602591, 0.0767994186031903, 0.0482516061458583, 0.101439036467562, 0.811302368396859); - const float min_ev = -12.47393; - const float max_ev = 4.026069; + // Combined inverse AgX outset matrix and linear Rec 2020 to linear sRGB matrices. + const mat3 agx_outset_rec2020_to_srgb_matrix = mat3( + 1.9648846919172409596, -0.29937618452442253746, -0.16440106280678278299, + -0.85594737466675834968, 1.3263980951083531115, -0.23819967517076844919, + -0.10883731725048386702, -0.02702191058393112346, 1.4025007379775505276); + + // LOG2_MIN = -10.0 + // LOG2_MAX = +6.5 + // MIDDLE_GRAY = 0.18 + 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) // Do AGX in rec2020 to match Blender. - val = LINEAR_SRGB_TO_LINEAR_REC2020 * val; - val = max(val, vec3(0.0)); + color = LINEAR_SRGB_TO_LINEAR_REC2020 * color; + + // Preventing negative values is required for the AgX inset matrix to behave correctly. + // This could also be done before the Rec. 2020 transform, allowing the transform to + // 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)); - // Input transform (inset). - val = agx_mat * val; + color = agx_inset_matrix * color; // Log2 space encoding. - val = max(val, 1e-10); - val = clamp(log2(val), min_ev, max_ev); - val = (val - min_ev) / (max_ev - min_ev); + color = max(color, 1e-10); // Prevent log2(0.0). Possibly unnecessary. + // Must be clamped because agx_blender_default_contrast_approx may not work well with values above 1.0 + color = clamp(log2(color), min_ev, max_ev); + color = (color - min_ev) / (max_ev - min_ev); // Apply sigmoid function approximation. - val = agx_default_contrast_approx(val); + color = agx_default_contrast_approx(color); - return val; -} + // Convert back to linear before applying outset matrix. + color = pow(color, vec3(2.4)); -vec3 agx_eotf(vec3 val) { - const mat3 agx_mat_out = mat3( - 1.1271005818144368, -0.1413297634984383, -0.1413297634984383, - -0.1106066430966032, 1.1578237022162720, -0.1106066430966029, - -0.0164939387178346, -0.0164939387178343, 1.2519364065950405); + // Apply outset to make the result more chroma-laden and then go back to linear sRGB. + color = agx_outset_rec2020_to_srgb_matrix * color; - val = agx_mat_out * val; + // Simply hard clip instead of Blender's complex lusRGB.compensate_low_side. + color = max(color, vec3(0.0)); - // Convert back to linear so we can escape Rec 2020. - val = pow(val, vec3(2.4)); - - val = LINEAR_REC2020_TO_LINEAR_SRGB * val; - - return val; -} - -// Adapted from https://iolite-engine.com/blog_posts/minimal_agx_implementation -vec3 tonemap_agx(vec3 color) { - color = agx(color); - color = agx_eotf(color); return color; }