I’m sorry, now we’re not just simulating rays to trace, we’re emulating simulating rays to trace? How is that more efficient?! Computer science == warlockry, change my mind.

Written by Michael Larabel in Radeon on 10 April 2025 at 05:46 AM EDT. 12 Comments RADEON Mesa’s Radeon Vulkan driver “RADV” is now exposing its emulated ray-tracing support by default for older AMD Radeon GPUs even without any form of hardware-accelerated ray-tracing in order to run the new Indiana Jones game. It turns out even the emulated RT mode is fast enough to allow various older AMD Radeon graphics cards to be playable with this title.

Natalie Vock has landed the change to expose the emulated Vulkan ray-tracing extensions by default when running Indiana Jones and The Great Circle “TGC”. Indiana Jones and the Great Circle was released for Windows back in December and powered by the Motor Engine. It requires ray-tracing support but it turns out RADV’s emulated support is good enough for allowing older GPUs to enjoy this action-adventure game.

Indiana Jones The Great Circle logo

Vock explained in the merge request:

"Various people have been playing Indiana Jones: The Great Circle with RADV_PERFTEST=emulate_rt on GFX9/GFX10. RT support is required to launch the game, and performance is okay even with emulation, so enable it by default to make the game playable for everyone running older (GFX8-10) GPUs."

AMD GFX8 is for the Polaris GPUs along with Volcanic Islands and Arctic Islands. Amazing to see AMD Radeon RX 480/580 Polaris GPUs still working for newer games on Linux.

This change is now in Mesa 25.1-devel while those on current Mesa releases with older Radeon GPUs can always set the RADV_PERFTEST=emulate_rt environment variable to achieve the same behavior.