Ray tracing can run without a GPU, if you like slideshows — Quake II RTX demoed at 1 FPS with CPU-based ray-tracing
by from Tomshardware on (#6K6PH)
A Mesa 3D Graphics Library developer has implemented support for CPU-based ray-tracing in Vulkan. In early testing of the driver in Quake II RTX only 1FPS performance was achieved, but it's a start.