* Change #define constant value to static constexpr
* Adds const where possible
* Uses reference instead of pointer where possible
* Uses `float3` instead of raw float array where possible
* Uses std::optional to indicate value that may be null
* Reduces scope of variables where possible
* Uses `std::array` instead of raw arrays where possible
* Combines assignment and declaration where possible
* Lengthens some names from single letters
Pull Request: https://projects.blender.org/blender/blender/pulls/135486
5546fe9848