Real-Time Ray Tracing : Holy Grail or Fools' Errand?

Friday 12th October 2007, 10:10:00 AM, written by Dean Calver

With Intel making noise about acceleration of real-time ray tracing in recent months, especially where it concerns future hardware they're working on, DeanoC found himself a little puzzled as to why.

Pitting real-time Whitted RT vs traditional real-time rasterisation, Deano's article compares the two approaches to see where the pros and cons of each approach lie. Should we be hailing our future shiny ball overlords, or does recent RT chatter need a bit more to back it up?

Have a read and find out!

Discuss on the forums

Tagging

b3d ± deanoc, whitted, ray, tracing, rasterisation


Latest Thread Comments (221 total)
Posted by Betanumerical on Monday, 20-Apr-09 22:59:44 UTC
Quoting MfA
It's not a prototype, they are selling it ... and they shouldn't have allowed their PR staff to try to hide it was a FPGA.
Its a prototype for developers.

Posted by digitalwanderer on Monday, 20-Apr-09 23:03:43 UTC
That they're selling?

Posted by hoho on Tuesday, 21-Apr-09 13:51:49 UTC
Quoting Arnold Beckenbauer
Caustic Graphics Ray Tracing Acceleration Technology Review (http://www.pcper.com/article.php?aid=694&type=expert&pid=1)
Opinions?
They use 8 CPU cores and at least 2 FPGA's and can't reproduce stuff that people are doing using the same amount of CPU cores and zero FPGA's. Their only hope is that the next version will have insane scalability and can do much more work on the die so that CPU won't be a bottleneck any more.

Posted by Scali on Tuesday, 21-Apr-09 16:00:54 UTC
This article gives some insight in how these cards are used:
http://www.extremetech.com/article2/0,2845,2345640,00.asp

Apparently the chips are used to accelerate some portions of the raytracing process, but the actual shading is done on the CPU (and in the future can be done on the GPU).
It seems that their hardware mainly reorders rays so that they can be processed efficiently in parallel by conventional CPUs and GPUs. They use the word 'scheduler'.

Posted by Heinrich4 on Wednesday, 22-Apr-09 14:49:47 UTC
Quoting Scali
This article gives some insight in how these cards are used:http://www.extremetech.com/article2/0,2845,2345640,00.aspApparently the chips are used to accelerate some portions of the raytracing process, but the actual shading is done on the CPU (and in the future can be done on the GPU).It seems that their hardware mainly reorders rays so that they can be processed efficiently in parallel by conventional CPUs and GPUs. They use the word 'scheduler'.
Thanx for posting this article.Finnaly one of first steps going to RT... im pray here for some day we could see a mature hardware (or hybrid with Raster...) doing true RT(60 to 200 rays/pixel).(what level opemRT /saarcor guys going in your RT engine? It does exist today?)

Posted by Scali on Wednesday, 22-Apr-09 15:30:07 UTC
A similar article on Arstechnica:
http://arstechnica.com/hardware/news/2009/04/caustic-graphics-launches-real-time-ray-tracing-platform.ars

Also, the business plan is apparently to start with these FPGA-based cards (Caustic One), because they're cheap to build... then build an ASIC card (Caustic Two) if there is enough demand.
Because the chip doesn't really rely on tons of bandwidth and tons of parallel SIMD processing power (those things are basically delegated to the CPU or GPU performing the actual shading and other tasks), it doesn't have to be a very big, cutting-edge chip. They want to build the ASIC on 90 nm, running at about 350 MHz, which should be more than 10 times as fast as the current FPGA.

Posted by Joker B on Saturday, 25-Apr-09 01:50:05 UTC
A curious business case in that article about game level design. Secret Level made a level lighter that was GPU based. Big win. Otavio Good showed at @ XNA game fest a couple of years ago: http://www.secretlevel.com/downloads/Natural%20Outdoor%20Lighting%20in%20Games.zip

What's not clear here is why a raytracer would be a better choice... unless it was used slowly for AO or something like that. And you'd still have to write the software and integrate it into your pipeline.

Or just buy Beast.

Natural lighting isn't what's usually desired. Look at the average live-action movie crew. The big lighting trucks contain a few lamps and a LOT of equipment (and people) who are there to PREVENT natural light. Believable, yes. Natural, no.

Posted by PhilTaylor on Friday, 15-May-09 01:19:18 UTC
[QUOTE=Joker B;1289243]

What's not clear here is why a raytracer would be a better choice...
QUOTE]

some effects are just easier with a tracer.

reflections and refractions are pretty trivial in a tracer and are much, much harder to get right in a triangle engine.

cubemap reflections, for instance, dont typically have an accurate point of view for all camera positions as the cubemap is rendered from one pov.

and who knows, might even affect gameplay if done accurately in a tracer

Posted by MfA on Friday, 15-May-09 12:49:41 UTC
Quoting Joker B
Natural lighting isn't what's usually desired. Look at the average live-action movie crew. The big lighting trucks contain a few lamps and a LOT of equipment (and people) who are there to PREVENT natural light. Believable, yes. Natural, no.
Interactive games are fundamentally different because the viewpoint tends to be arbitrary.

Posted by Scali on Friday, 15-May-09 12:58:52 UTC
Quoting Joker B
Natural lighting isn't what's usually desired. Look at the average live-action movie crew. The big lighting trucks contain a few lamps and a LOT of equipment (and people) who are there to PREVENT natural light. Believable, yes. Natural, no.
Exactly, I read a nice paper from Dreamworks a few years ago, about the lighting used in Shrek, and how they like to control the lighting accurately with simple pointlights or spotlights, rather than going for GI/'physically accurate' solutions.


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