After hearing about Ray-Tracing being used during the Showroom in GT5, and during gameplay in Killzone2, i started to look around and read some articles on Ray-Tracing and how it affects games and various aspects of how the game looks and runs.  Using Ray-Tracing and its aspects its able to greatly reduce the workload on the GPU/CPU allowing it too work on other aspects of the game.  It also allows the games to match high AA, its able to re-create textures for importance and how each looks for where the user is in the level.

But the one thing i read in these articles is that real time Ray-tracing is too hard to do with modern computers, they mention that some aspects of it are used but they can cause bad effects in the game.  The articles i read are from late 2006/2007. 

But i would assume that Ray-Tracing is going on in computer games now, since the PS3 has used it.  But i have yet to find an article that says aout it being used.

But is Ray-Tracing a step in the right direction or is it useless for modern gaming and too hard to use in real time without using too many resources to get it working.

Intel have shown some ray-tracing demos not long ago, and they seem to be pretty optimistic about ray-tracing as the future, pushing the tech through their future hardware, their first dedicated GPU code-named Larrabee slated for I think 2010, a very CPU-like grafix card.

Here are very new Ruby demos from AMD showing ray tracing (on current HW, one or more 4870's I believe):

 This is amazing, but I don't know if it is ray tracing in real time (did anyone catch that from the interview?):
(a new motion capture technique by AMD to render ray traced models)

But then you have this recent interview with John Carmack (the 3D-programming guru of our age for those who didn't know). He seems quite negative in general, and is basically saying that he hasn't seen much concrete proof neither on the HW or SW side about ray tracing being a realistic solution in gaming in the near future (=next gen), although he is himself experimenting with partial use of ray tracing in gaming-like applications.

John Carmack on id Tech 6, Ray Tracing, Consoles, Physics and more (Mar 12, 2008)
http://www.pcper.com/article.php?aid=532&type=expert

Raytracing uses an algorithm that is characterized as 'Embarrasingly Parallel'

Furthermore, the Cell SPEs happen to be very well-suited to the math required for Ray Tracing.

When you put 1 and 2 together, you get a situation where in certain instances, ray tracing can be much (computationally) cheaper on the PS3 than on other systems.

Keep in mind though; it is still VERY expensive computationally. It is likely only viable even on the PS3 if you need less computation for the main game, to the point of being able to give up several of the SPEs; if you want to use Ray Tracing, you would likely need to use the majority of the SPEs to do it, leaving them unable to be used for other parts of the game (which may not be necessary to begin with, but some devs have used them for generic computation, so depending on the game it may not be possible)

Well, I have been working on ray-tracer for a while and yes it is beyond the scope of todays computers(higher resolutions). Ray-tracing gives some nice things like mirrors 'for free' but in balance theres stuff you really can't do with ray-tracing without very expensive algorithms(antialiasing for example).

The main things that make ray-tracing expensive are resolution and how long you trace each ray.

Well, technically, simple AA can be done by rendering subpixel accuracy thought it requires about 4x the amount of processing to do one pixel 4 times.  You could apply some cheap bluring effects on objects within close proximity, but it doesn't always come out looking like it should.  It's not necessarily hard (in fact, raytracing if incredibly easy from my experience) but it can be very hardware intensive to get lifelike results.  I'm actually looking forward to testing out some of my rendering engines with the Larabee.  So far I've only been testing with my dual quad Core2 and I can say we are pretty close, but we still need just a bit more processing power.

Well, I might have you a nice suggestion. Use shaders to get more power. As video cards don't need to rasterize images they are 'free' to help you with ray tracing. If you are not fond with shaders, you could always use CUDA too. I am making raytracer 'as a bonus' for my raster based 3D engine. :)

I used YafRay.

(Extent of Rath's knowledge on ray tracers)