6967255906
This implements a von-Kries-style chromatic adaption using the Bradford matrix. The adaption is performed in scene linear space in the OCIO GLSL shader, with the matrix being computed on the host. The parameters specify the white point of the input, which is to be mapped to the white point of the scene linear space. The main parameter is temperature, specified in Kelvin, which defines the blackbody spectrum that is used as the input white point. Additionally, a tint parameter can be used to shift the white point away from pure blackbody spectra (e.g. to match a D illuminant). The defaults are set to match D65 so there is no immediate color shift when enabling the option. Tint = 10 is needed since the D-series illuminants aren't perfect blackbody emitters. As an alternative to manually specifying the values, there's also a color picker. When a color is selected, temperature and tint are set such that this color ends up being balanced to white. This only works if the color is close enough to a blackbody emitter - specifically, for tint values within +-150. Beyond this, there can be ambiguity in the representation. Currently, in this case, the input is just ignored and temperature/tint aren't changed. Ideally, we'd eventually give UI feedback for this. Presets are supported, and all the CIE standard illuminants are included. One part that I'm not quite happy with is that the tint parameter starts to give weird results at moderate values when the temperature is low. The reason for this can be seen here: https://commons.wikimedia.org/wiki/File:Planckian-locus.png Tint is moving along the isotherm lines (with the plot corresponding to +-150), but below 4000K some of that range is outside of the gamut. Not much can be done there, other than possibly clipping those values... Adding support for this to the compositor should be quite easy and is planned as a next step. Pull Request: https://projects.blender.org/blender/blender/pulls/123278
44 lines
886 B
C++
44 lines
886 B
C++
/* SPDX-FileCopyrightText: 2022 Blender Authors
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*
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* SPDX-License-Identifier: GPL-2.0-or-later */
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#ifndef GPU_SHADER
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# include "GPU_shader_shared_utils.hh"
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#endif
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struct OCIO_GPUCurveMappingParameters {
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/* Curve mapping parameters
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*
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* See documentation for OCIO_CurveMappingSettings to get fields descriptions.
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* (this ones pretty much copies stuff from C structure.)
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*/
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float4 mintable;
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float4 range;
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float4 ext_in_x;
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float4 ext_in_y;
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float4 ext_out_x;
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float4 ext_out_y;
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float4 first_x;
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float4 first_y;
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float4 last_x;
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float4 last_y;
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float4 black;
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float4 bwmul;
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int lut_size;
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int use_extend_extrapolate;
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int _pad0;
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int _pad1;
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};
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struct OCIO_GPUParameters {
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float dither;
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float exponent;
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bool32_t use_predivide;
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bool32_t use_overlay;
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bool32_t use_hdr;
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int _pad0;
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int _pad1;
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int _pad2;
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float4x4 scene_linear_matrix;
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};
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