Ray tracing has long been "proven" only to be playable on GPUs boasting hardware-accelerated ray-tracing capabilities. However, AMD GPUs dating back to the first GCN-based graphics cards (including GPUs such as the Radeon HD 7970) have been capable of running ray tracing for a while through software emulation. Clewless Clay on YouTube brought this fact to our attention, and several sources demonstrate ray-tracing on older AMD GPUs, including a Vega 64 graphics card running Indiana Jones and the Great Circle at well over 30 FPS.
The software-based ray-tracing implementation offers surprisingly potent performance. One YouTuber fittingly named "no RTX no problem" shared a video of an RX Vega 64 running Indiana Jones and the Great Circle in Linux Fedora 41 at 1080p with 50% resolution scaling (720p internal resolution) with medium graphics settings at playable frame rates. Frame rates hovered anywhere between 50 to 60 FPS average.
Another YouTuber, BK Benchmark, showed an RX 5700 XT running the same game with identical settings but at native 1080P resolution (100% scaling). The newer GPU demonstrated significantly better performance, hovering in the 70 to 80 FPS range on average.
Ray tracing emulation exists through Linux's RADV driver, an open-source counterpart to AMD's official AMDVLK reference Linux driver (significantly expanding AMD GPU capabilities in Linux). Ray tracing support on non-RT supported AMD GPUs was allegedly the brainchild of Joshua Ashton, known for his work on Proton and DXVK. Phoronix reported that adapting AMD's Linux-based RADV driver to run emulated RT was not difficult for the developer. Ashton's RADV ray tracing emulation is achieved by emulating AMD BVH intersection instructions in software.
Joshua Ashton allegedly started experimenting with RT emulation support in 2021, adding support for architectures dating back to GCN 1.0 in 2022. By 2023, his RT emulation development reached full stability, achieving a "100% pass rate" (according to Phoronix). The feature can even be activated on RDNA2 and RDNA3 for benchmarking purposes using the "emulate_rt" debug option.
Linux's RT-emulation on AMD GPUs is not a competitive solution against newer GPUs sporting hardware-baked ray tracing acceleration. However, the technology has major implications for making modern games playable on older graphics cards. Indiana Jones and the Great Circle is a great example, being one of the first (if not the first) titles to require a ray-tracing capable graphics card. If this trend continues, we can expect future titles to boast the same requirement. Emulating ray tracing will be the only way to make these future games playable on non-RT accelerated GPUs, assuming the ray-traced lighting in future games can be tuned down to playable levels.
However, the biggest hurdle of this RT-emulation implementation is that it only supports Linux operating systems, being an open-source Linux-specific driver. Apparently, there is no work being done to bring such a feature to Windows 10 or Windows 11 (in an official or open-source manner), and there is no work being done to offer this capability on Nvidia GTX graphics cards, limiting its functionality to the niche group of users running Linux on pre-RDNA2-based AMD graphics cards.
