Building without GPU support

[rgwilson68]

The standard MoonRay build includes CUDA/Optix support for XPU mode and GPU denoising. However, MoonRay automatically falls back to a non-XPU mode if it doesn't find a suitable GPU device on the machine, so you can use this build even on machines that don't have a GPU.

It is possible to build without GPU support - MoonRay then won't use a GPU even if one is present, but it means you can perform the build without needing to download and install CUDA/Optix libraries. The CMake option MOONRAY_USE_CUDA controls this, so to configure a non-GPU build you would use:

cmake --preset container-release -DMOONRAY_USE_CUDA=NO

in place of 'cmake --preset container-release'.

Disabling CUDA support means you can skip the install of 'cuda-toolkit-11-4' (i.e. remove that line from the Dockerfile for a container build, or just skip it for a non-container build). You can also skip downloading and copying the Optix headers.

For a non-CUDA container build, you can start with a plain Centos-7 base image, instead of the nvidia/cuda image -- replace the first line of Dockerfile with;

FROM centos:7

The denoise command will not support optix mode in a non-CUDA build, but you can still use it in "oidn" mode.

As noted in the documentation, you can use -DBUILD_QT_APPS=NO in a similar way to skip building the Qt GUI applications and avoid the need to install Qt prior to building.