CPU real-time ray-tracing is here, but performance in Quake 2 RTX sits at 1 FPS

Real-time ray-tracing with just a CPU is possible with the latest Mesa CPU-based Vulkan driver, but performance is terrible without hardware acceleration.

1 minute & 36 seconds read time

Real-time ray tracing has been one of the biggest advances in GPU rendering and PC gaming in the past decade. Due to the sheer hardware grunt required to achieve it, it kickstarted the push into the world of DLSS AI-powered upscaling and Frame Generation.

Quake II RTX runing on a CPU = 1FPS with a frame time of over 1600ms, image credit: Konstantin Seurer.

Quake II RTX runing on a CPU = 1FPS with a frame time of over 1600ms, image credit: Konstantin Seurer.

In 2024, we're at the point where some high-end GPUs in the GeForce RTX line-up can run games like Cyberpunk 2077 and Alan Wake II with full path-traced lighting, offering a glimpse into the future of immersive game visuals. So, the idea of real-time ray-tracing or going "RTX On" with just a CPU sounds like a recipe for poor performance.

And that's what you've got with the latest Mesa 3D Graphics Library and its Vulkan driver-CPU-level support for ray tracing. The library ports the work to support ray tracing on older Radeon GPUs to CPUs, with Mesa developer Konstantin Seurer writing 'don't ask about performance' underneath a Quake II RTX screenshot.

Quake II RTX is an NVIDIA-developed real-time ray-tracing mod for id Software's iconic shooter. It was released alongside its GeForce RTX 20 Series debut, pre-dating the rise of DLSS rendering to boost performance.

The screenshot shows Vulkan RT performance is 1 FPS with a frame time of over 1600ms. According to someone who contacted the developer, the CPU used was the Ryzen 5600X, and the overlay reported incorrect data. The actual performance was closer to one frame every 15 minutes.

Interestingly, Intel showcased a ray-traced version of Enemy Territory: QUAKE Wars back in 2008 (shout out to Videocardz for remembering this), with Team Blue able to get that running at close to 30 FPS at 720p on a 24-core CPU. And seeing as integrated GPUs in 2024 are more powerful than ever, ray-tracing without a discrete GPU (with decent performance) is simply a matter of when.

The CPU-based Vulkan ray-tracing will be available in the upcoming Meda 24.1 release, though don't expect it to lead to CPU-based RT gaming.

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Kosta is a veteran gaming journalist that cut his teeth on well-respected Aussie publications like PC PowerPlay and HYPER back when articles were printed on paper. A lifelong gamer since the 8-bit Nintendo era, it was the CD-ROM-powered 90s that cemented his love for all things games and technology. From point-and-click adventure games to RTS games with full-motion video cut-scenes and FPS titles referred to as Doom clones. Genres he still loves to this day. Kosta is also a musician, releasing dreamy electronic jams under the name Kbit.

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