How Quake Wars Met the Ray Tracer

An anonymous reader writes "Intel released the article 'Quake Wars Gets Ray Traced' (PDF) which details the development efforts of the research team that applied a real-time ray tracer to Enemy Territory: Quake Wars. It describes the benefits and challenges of transparency textures with this rendering technology. Further insight is given into what special effects are most costly. Examples of glass and a 3D water implementation are shown. The outlook hints into the area of freely programmable many-core processors, like Intel's upcoming Larrabee, that might be able to handle such a workload." We mentioned the ray-traced Quake Wars last in June; the PDF here delves into the implementation details, rather than just showing a demo, and explains what parts of the game give the most difficulty in going from rasterization to ray-tracing.

Comments

Never ending chase...

[grumbel]

Yet another ray tracing article and yet again all the same problems as before. Doing yesterday games in ray tracing is all nifty, but also kind of pointless. For one we already played them, but more importantly, it doesn't actually use the strength of ray tracing. Rendering a tree build out of texture quads is a nice accomplishment, but wasn't the whole point of ray tracing that one can have a million polygons and no longer need such hacks? So show me a realistic tree instead of trying to replicate the limitations of rasterization.

I am still waiting for a game/demo that actually is build from the ground up with ray tracing in mind and by that I mean one that actually looks good, just a few shiny spheres might have been impressive back on the Amiga some 20 years ago, not any more.

Re:Never ending chase...

[Sycraft-fu]

You aren't going to see that kind of thing in a game for many reasons that boil down to that ray tracing isn't ready to do realtime. To make a game that used ray tracing would pretty much doom it to failure.

One problem you have is that the graphics hardware out there isn't built for ray tracing, it's built for rasterization. Now while I'm sure you can write your own ray tracer on the newer hardware that does GPGPU stuff, I'm also sure it wouldn't run as well. Reason is that current graphics cards are purpose built rasterizers. They are designed to do that as fast as possible. So you are left with writing your own ray tracing engine in software, either on the CPU or GPU. This is not going to be fast, especially since ray tracking is fairly computationally intensive.

Well then you hit the next problem: Pixels. Ray tracers do NOT scale well with resolution. Each pixel has to have it's own ray cast. If you want to do anti-aliasing, then you have to do more rays for that. This is why ray tracing demos tend towards low resolutions. It is much faster the less pixels you have to do. Ok well that doesn't compare favorably against the rasterizers. They scale extremely well with resolution, and also in terms of anti-aliasing. Many of them can do 4xFSAA with next to no performance penalty, and can do it at full HD resolutions. Not the case with your ray tracer. If it can render 40 FPS at 1920x1200 with no AA, it'll be just 10 FPS with 4x AA since it now has to do 4 rays per pixel.

So you aren't going to see it happen any time soon. The net result wouldn't look as good as the equivalent rasterized game. It won't be the sort of thing you see until either there starts to be purpose built ray tracing hardware (GPUs may start be made for both) or general purpose processors are so fast it makes no real difference.

Intel is all up on this because they see GPUs as a threat to their computation market. However, as this demonstrates here, there really isn't an advantage at this time. You throw a positively massive system at it and you get poor performance. Even if you redid the game so it used extremely high geometry, nobody would give a shit. IT would run way too slow on any normal computer.