Carmack On 'Infinite Detail,' Integrated GPUs, and Future Gaming Tech 149
Vigile writes "John Carmack sat down for an interview during Quakecon 2011 to talk about the future of technology for gaming. He shared his thoughts on the GPU hardware race (hardware doesn't matter but drivers are really important), integrated graphics solutions on Sandy Bridge and Llano (with a future of shared address spaces they may outperform discrete GPUs) and of course some thoughts on 'infinite detail' engines (uninspired content viewed at the molecular level is still uninspired content). Carmack does mention a new-found interest in ray tracing, and how it will 'eventually win' the battle for rendering in the long run."
Ray Tracing != Ray Casting (Score:5, Informative)
It should be noted that John Carmack believes that Ray Casting, not Ray Tracing, will win out in the long term.
Unfortunately, many people outside of the graphics field confuse the two. Ray Casting is a subset of Ray Tracing in which only a single sample is taken per pixel, or in other words, in which a single ray is cast per pixel into the scene and a single intersection is taken with the geometry data set (or in the case of a translucent surface, the ray my be propagated in the same direction a finite number of times until an opaque surface is found). No recursive bouncing of rays is done. Lighting is handled through another means, such as with traditional forward shading against a dataset of light sources, or using a separate deferred shading pass to un-hinge the combinatorial explosion of overhead caused by scaling up the number of lights in a scene.
John Carmack has been quoted on saying that full-blown ray-tracing just isn't feasible for real-time graphics due to the poor memory access patterns involved, as casting multiple rays per pixel, with multiple recursive steps ends up touching a lot of memory in your geometry data set, which just thrashes the cache on CPU and modern/future GPU hardware alike.
When people talk about real-time ray-tracing, they almost always invariably are referring to real-time ray-casting.
Re:Ray Tracing != Ray Casting (Score:4, Informative)
The video you posted is not real-time frame rates, it's interactive frame rates. It takes a few seconds to fully recompute the scene once you stop moving the camera. And note how there's only a single car model. imagine scaling up the amount of geometry to a full world. With ray-tracing, as you scale up the complexity of the geometry, you end up scaling up the required computational complexity as well due to radiosity computations. Full real-time ray-tracing on huge worlds in real-time is a pipe-dream. What you will be able to do with ray-casting or rasterization with deferred shading composition to simulate things like reflections or radiosity will always be more than what you can do with ray-tracing, and so games developers will always choose the former.