Previously, GPU denoisers were ignoring settings about render
configuration and were using any available GPU. With these changes,
GPU denoisers will use the device selected in Blender Cycles
settings.
This allows any GPU denoiser to be used with CPU rendering.
Pull Request: https://projects.blender.org/blender/blender/pulls/118841
Cycles already treats denoising fairly separate in its code, with a
dedicated `Denoiser` base class used to describe denoising
behavior. That class has been fully implemented for OIDN
(`denoiser_oidn.cpp`), but for OptiX was mostly empty
(`denoiser_optix.cpp`) and denoising was instead implemented in
the OptiX device. That meant denoising code was split over various
files and directories, making it a bit awkward to work with. This
patch moves the OptiX denoising implementation into the existing
`OptiXDenoiser` class, so that everything is in one place. There are
no functional changes, code has been mostly moved as-is. To
retain support for potential other denoiser implementations based
on a GPU device in the future, the `DeviceDenoiser` base class was
kept and slightly extended (and its file renamed to
`denoiser_gpu.cpp` to follow similar naming rules as
`path_trace_work_*.cpp`).
Differential Revision: https://developer.blender.org/D16502
