John Carmack's Comment on Hardware Ray Tracing
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John Carmack's Comment on Hardware Ray Tracing
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Re: John Carmack's Comment on Hardware Ray Tracing
#2Its so cool that someone as high up in the games industry as carmack actually knows his technical shit.
Re: John Carmack's Comment on Hardware Ray Tracing
#3Excellent response by Carmack.
"Ray Tracing" has always been an overhyped or misunderstood technology, at least in my experience. Because of the impressive lighting effects it's famous for producing, people view it as some "holy grail" of superior computer graphics technology that we just need to optimize a bit for use in games.
As Carmack described, those highly realistic ray traced renders come at a price: billions of ray calculations. You don't get all that pixel-perfect refraction, etc. for free (and probably never will - at least not with ray tracing.) He also explains that for most people, this (e.g. pixel perfect refraction) really doesn't matter, when rasterization techniques exist that achieve extremely high quality approximations at a fraction of the computational cost.
Conversely though, ray tracing and related concepts (ray casting) are not at all without value. Many modern video games today actually use a sort of hybrid rasterization / ray casting approach. Macrostructure objects are rasterized the normal way, while smaller high resolution detail patterns (like a brick wall, or stones in the ground) are "added" to surfaces via per-pixel displacement mapping, which is ray casting at its core. This is one of the few cases where you can take advantage of the "log2" efficiency Carmack mentioned -- in a highly specialized implementation without a huge time constant.
Re: John Carmack's Comment on Hardware Ray Tracing
#4Its so cool that someone as high up in the games industry as carmack actually knows his technical shit.
He might be high up now, but he started off as a programmer. He co-founded id software and (along with others) developed Wolfenstein 3D, Doom, etc. http://en.wikipedia.org/wiki/Id_Software
Re: John Carmack's Comment on Hardware Ray Tracing
#5Having no real knowledge of ray tracing (or rendering for that matter), can someone tell me why we can't be moving towards a massive cluster of gpu (in the order of 10,000) ray tracing a scene in parellel? I imagine each ray trace call is quite independent of any other. SOooner or later, cpu (and gpu) will have many cores available for such form of rendering. Is it because of the chicken/egg problem?
Re: John Carmack's Comment on Hardware Ray Tracing
#6Its so cool that someone as high up in the games industry as carmack actually knows his technical shit.
He might be high up now, but he started off as a programmer. He co-founded id software and (along with others) developed Wolfenstein 3D, Doom, etc. http://en.wikipedia.org/wiki/Id_Software
He still is a programmer. He's the lead programmer at id and writes code for Armadillo Aerospace.
Re: John Carmack's Comment on Hardware Ray Tracing
#7Its so cool that someone as high up in the games industry as carmack actually knows his technical shit.
He might be high up now, but he started off as a programmer. He co-founded id software and (along with others) developed Wolfenstein 3D, Doom, etc. http://en.wikipedia.org/wiki/Id_Software
Not only that but I believe he is still "in the trenches" and cuts industry leading code to this day.
Re: John Carmack's Comment on Hardware Ray Tracing
#8Having no real knowledge of ray tracing (or rendering for that matter), can someone tell me why we can't be moving towards a massive cluster of gpu (in the order of 10,000) ray tracing a scene in parellel? I imagine each ray trace call is quite independent of any other. SOooner or later, cpu (and gpu) will have many cores available for such form of rendering. Is it because of the chicken/egg problem?
I think that's what he's implying when he says
I am 90% sure that the eventual path to integration of ray tracing hardware into consumer devices will be as minor tweaks to the existing GPU microarchitectures.Re: John Carmack's Comment on Hardware Ray Tracing
#9Having no real knowledge of ray tracing (or rendering for that matter), can someone tell me why we can't be moving towards a massive cluster of gpu (in the order of 10,000) ray tracing a scene in parellel? I imagine each ray trace call is quite independent of any other. SOooner or later, cpu (and gpu) will have many cores available for such form of rendering. Is it because of the chicken/egg problem?
AMD's vision of "heterogenous computing"(I think they came up with a new name for this?) would essentually be the "true" fusion of a CPU and a GPU in a sense that the chip consists of general purpose execution units(current CPU cores) and of special purpose parallel processing units (curent GPU SIMD/VLIW units) which operate concurrently in such sense that both sequential and parallel code can be executed efficiently on per-thread basis and as threads processed concurrently.
Something like this would really help with things like raytracing. But then again, as Carmack mentions, the huge disadvantage are the acceleration structures which need to be discarded and rebuilt per frame for dynamic objects. It's like saying that raytracing is by it's nature inferior(or at least very wasteful) from performance point of view. It's like a problem to which you simply don't say "Just throw more hardware at it!".
Re: John Carmack's Comment on Hardware Ray Tracing
#10Having no real knowledge of ray tracing (or rendering for that matter), can someone tell me why we can't be moving towards a massive cluster of gpu (in the order of 10,000) ray tracing a scene in parellel? I imagine each ray trace call is quite independent of any other. SOooner or later, cpu (and gpu) will have many cores available for such form of rendering. Is it because of the chicken/egg problem?
You would need all nodes to hold almost all geometry, even when you achieve this, you would have to cut the screen into 10,000 pieces of pixels, and then trace each one individually. Some of these small ares would finish much faster than the others, and it would be hard to move them to do another job (or expensive).
But that's from my simple understanding, possibly there would be other problems too...