Anything a CPU can do, the GPU can do. But better?
As well as affording us an indepth look at Intel’s forthcoming GPU, Larrabee, this year’s Special Interest Group on GRAPHics (SIGGRAPH) conference has seen nVidia showing off a real-time ray tracing demo to attendees. The aim of the demo, though, seems not so much to have been to prove that ray-tracing is possible on the GPU, but rather that it is still extremely unviable.
The demo itself comprised a render of a green Bugatti Veyron at a resolution of 1,920 x 1,080 running at 30fps. In order to run in this way, though, nVidia needs an extremely powerful system: namely an nVidia Quadro Plex 2100 D4 Visual Computing System, which packs in a pair of dual-GPU Quadro FX 4700 X2s. In simple terms: a heck of a lot of GPU processing power.
Despite this huge amount of processing power available, nVidia still isn’t able to produce a photorealistic image in real-time. In order to run at 30fps at 1080p, the demo uses three bounces for each ray (i.e. each beam of light reflects off three surfaces before ‘hitting’ the screen). To create a realistic image, more reflections need to be calculated – but doing so would turn the simulation into a slideshow.
nVidia does have the edge over Intel’s CPU-based Quake ray-tracing demo, which only ran at 720p, between 14 and 30 FPS and needed a four-socket quad quad-core system to run. But, as I said, nVidia is pointing out that ray-traced games are still some way off, not that GPUs ray-trace better than CPUs. Despite the hype around Larrabee’s potential use as a ray-tracing card.