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srgb_to_linearrgb_v3_v3 is using an approximation of powf that is SIMD. However, while the accuracy of it is ok, a larger issue is that it produces different results on Intel compared to ARM architectures. On ARM (e.g. AppleSilicon), the result of the SIMD code path is much closer to the reference implementation. This seems to be because of _mm_rsqrt_ps usage in _bli_math_fastpow512. The ARM/NEON code path emulates inverse square root with a combination of vrsqrteq_f32 followed by two Newton-Raphson iterations, because blender uses the SSE2NEON_PRECISE_SQRT define. This commit adds similar NR iterations to the "actual SSE" code path as well. Max error of srgb->linear->srgb conversion roundtrip goes from 0.000211 down to about 0.000062. Reviewed By: Sergey Sharybin Differential Revision: https://developer.blender.org/D15193
.. Keep this document short & concise, linking to external resources instead of including content in-line. See 'release/text/readme.html' for the end user read-me. Blender ======= Blender is the free and open source 3D creation suite. It supports the entirety of the 3D pipeline-modeling, rigging, animation, simulation, rendering, compositing, motion tracking and video editing. .. figure:: https://code.blender.org/wp-content/uploads/2018/12/springrg.jpg :scale: 50 % :align: center Project Pages ------------- - `Main Website <http://www.blender.org>`__ - `Reference Manual <https://docs.blender.org/manual/en/latest/index.html>`__ - `User Community <https://www.blender.org/community/>`__ Development ----------- - `Build Instructions <https://wiki.blender.org/wiki/Building_Blender>`__ - `Code Review & Bug Tracker <https://developer.blender.org>`__ - `Developer Forum <https://devtalk.blender.org>`__ - `Developer Documentation <https://wiki.blender.org>`__ License ------- Blender as a whole is licensed under the GNU General Public License, Version 3. Individual files may have a different, but compatible license. See `blender.org/about/license <https://www.blender.org/about/license>`__ for details.