154 replies to this topic

[Altair]

Axel said:

And how do you want to update the scenetree for the raytracer in that cases?

Every time someone throws the word "dynamic" to raytracing discussion it has a devastating effect :D I agree 100% with davepermen that games are by nature dynamic and become more and more dynamic in the future. However, it's the raytracing that suffers from the dynamic nature because it relies heavily on precomputation in the fundamental level of the algorithm. Rasterizers are actually moving away from the precomputation (e.g. lightmaps) and can choose to use precomputation based on application.

I attended few raytracing courses at Siggraph this year and people seem to be stuggling with the same fundamental problems as years ago (e.g. efficiently building & updating KD-tree for raytracing). Also very basic things in games like skinning are conveniently pushed to background in raytracing discussions. Anyway, once we get those consumer class quantum computers in the market, raytracing problems are solved, but current 6 qubit test-lab quantum computers doesn't quite cut it yet :wink:

Juhnu et al, don't take me wrong, I totally wish we could have those raytracing units which could process rays cheaply as butter, but when the algorithm has fundamental performance flaws my hope is running quite thin.

juhnu said:

The first rasterizing GPUs were not really that impressive and lacked both speed and majority of features we can now expect to find from a consumer class hardware.

Btw, you are dead wrong here. I don't know where you pulled that argument and what was the first 3D HW you ever saw, but I think it was Pyramid 3D by BitBoys (-97) and I was totally impressed of the capabilities of that chip at the time. I would argue that rasterizing HW ~10 years ago was more capable than raytracing HW today :rolleyes:

Cheers, Altair

[anubis]

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I would argue that rasterizing HW ~10 years ago was more capable than raytracing HW today

Some would argue that if the same amount of money were spent on research and production of ray tracing we would be some place else now. You remind me of all those right wingers who claim that alternative energy is not possible because it does not generate enough output but fail to see that the amount of money spent on the development of nuclear power is uncomparably larger (note : I'm not calling you a right winger :)). To conclude : Just because there are no solutions right now to certain problems in ray tracing doesn't mean that they don't exist.

[Goz]

anubis said:

conclude : Just because there are no solutions right now to certain problems in ray tracing doesn't mean that they don't exist.

With all due respect ... it doesn't mean they do either ...

[Altair]

anubis said:

Some would argue that if the same amount of money were spent on research and production of ray tracing we would be some place else now.

Some people do argue about that indeed, but it sounds more like a convenient excuse for raytracing not taking off. Pyramid 3D was developed with low budget, something comparable to SaarCOR chip AFAIK AND ~10 years ago. I don't know much about ASIC engineering, but I would imagine it's easier/cheaper now than 10 years ago. Big companies like nVidia and Intel have also done research in the area so it's not unexplored area by HW manufacturers. For sure more money has been invested on raytracing HW research now than was invested for the first shipped commercial 3D rasterizer chip. Raytracing isn't new science either and the movie business also provides direct commercial motivation it.

So why no commercial HW raytracing chip has emerged? I don't think it's because HW manufacturers wouldn't want or hasn't invested on it, but because there are too many fundamental issues to begin with.

anubis said:

To conclude : Just because there are no solutions right now to certain problems in ray tracing doesn't mean that they don't exist.

That's right, but you need a bit more solid arguments to back that up if you want constructive conversation :wink: You can't just shy away from the fact that raytracing is fundamentally complex algorithm when compared to rasterization, and that complexity doesn't just fade away.

Cheers, Altair

[anubis]

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You can't just shy away from the fact that raytracing is fundamentally complex algorithm

I am not shying away from the fact that dynamic geometry is currently one of the biggest issues in ray tracing, but so were other things for raster graphics a few years back.

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when compared to rasterization, and that complexity doesn't just fade away.

By that arguement i could say that the whole move to programmable hardware is a bad one because it introcduces so much more complexity to the pipeline. Of course you pick on more complex problems with increasing hardware capabilities. It's the nature of computer science. But what you are claiming is that noone should try to optimize ray tracing because rasterizers are superior anyway (at least you seem to be feeling superior over "the poor souls" who don't follow the "enlightend" path). The matter of the fact though is that ray tracing provides some pretty elegant sollutions to problems that are addressed in a pretty hacked way right now.

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I attended few raytracing courses at Siggraph this year and people seem to be stuggling with the same fundamental problems as years ago

I found this years Siggraph courses interesting in the way that exactly the problems of dynamic scenes and animation were addressed, without creating a big cover up for the problems at hand. Mind you, I can only judge from the keynote presentations, since I don't have the money to fly over to america just for Siggraph.

[Altair]

anubis said:

I am not shying away from the fact that dynamic geometry is currently one of the biggest issues in ray tracing, but so were other things for raster graphics a few years back

Could you elaborate which "other things" are you referring to?

anubis said:

By that arguement i could say that the whole move to programmable hardware is a bad one because it introcduces so much more complexity to the pipeline.

That would be pretty marthyric but at least you would have kind of point there. Introducing more complex programmability to the pipeline comes with the expense of performance (transistors allocated for features vs. performance), but at least this complexity is optional in the fundamental level of the rasterizer.

anubis said:

But what you are claiming is that noone should try to optimize ray tracing because rasterizers are superior anyway.

I don't think I ever said that, but merely pointed out the fundamental issues in raytracing for its advocates, who doesn't seem to have good grasp of practical issues in computer graphics and who for some ridiculous reason seem to take it personally.

anubis said:

I found this years Siggraph courses interesting in the way that exactly the problems of dynamic scenes and animation were addressed, without creating a big cover up for the problems at hand.

Could you point me the references, because in the courses I attended they were "addressed" in very VERY vague/impractical way (i.e. test ray against each triangle in a skinned mesh, etc.)

Cheers, Altair

[NomadRock]

One can argue back and forth forever about what problems might or might not occur with hardware raytracing, but one thing is sure. In areas where even the highest end Nvidia card is not high enough and people have to use general purpose processors, ray tracing is the method of choice for high quality graphics. This is evidenced by every 3D animated film.

Hardware makers in all areas including graphics are looking for every way to parallelize the work, because we need more performance than we can get out of the silicone with just serial instructions. There have been some pretty amazing feats in parallel processing on board of the high end graphics cards, but it remains a fact that ray tracing can leverage parallel hardware much better than rasterization.

It is true that rasterization is currently the way to go for real time graphics and the fact that the hardware is already in place plays no small part in that conclusion. Ray tracing scales much better but it is true that rasterization is rediculously cheap for scenes with lower complexity in geometry and effects. It may be true that at the current state of the art rasterization hardware would still be faster than ray tracing hardware with the benefit of modern designs and budgets, but as we progress in demanded complexity and hardware ability rasterization as an algorithm just cannot compete with ray tracing.

This is not to say that ray tracing is the holy grail, however. I believe that even ray tracing will eventually need to be replaced with a more accurate model of light interaction withing the world. I think we will need to move to full on photon tracing. This would have the added benefit of allowing an unlimited number of views from each wave of photons. This may turn out to be ideal for massively multiplayer games of the future where all the photon tracing could be done on giant hardware behind the servers. But that is all just drooling on my part, and there is a good chance that this will not come while I am young enough to care :)

[anubis]

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Could you elaborate which "other things" are you referring to?

Come on now... this is rethoric. What do you want me to do ? Tell you about the algorithmic developments of the last years ?

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I don't think I ever said that, but merely pointed out the fundamental issues in raytracing for its advocates, who doesn't seem to have good grasp of practical issues in computer graphics and who for some ridiculous reason seem to take it personally.

I'm not sure what you are saying though... Rasterizing is more powerful currently ? Has a wider support ? I agree. But what is the point of saying that ? What do you want to tell the world ?

Excuse me if i misinterpreted you but it just sounds like you want to prove that rt tracing is futile. If that's not the case and you just want to point us to the problems at hand that's nice. Rest assured it's being worked on.

Btw, addressing others as foolish just because they don't share your point of view isn't proving your point one bit.

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Could you point me the references, because in the courses I attended they were "addressed" in very VERY vague/impractical way (i.e. test ray against each triangle in a skinned mesh, etc.)

Sure... http://www.openrt.de...otes/course.php

The sixth talk on that page is about dynamic scenes and animation.

[Goz]

NomadRock said:

One can argue back and forth forever about what problems might or might not occur with hardware raytracing, but one thing is sure. In areas where even the highest end Nvidia card is not high enough and people have to use general purpose processors, ray tracing is the method of choice for high quality graphics. This is evidenced by every 3D animated film.

Im sorry .. are you saying that 3D animated films are done using ray tracing?

REYES is a triangle subdivision rasteriser. Thought RenderMan was too ...

[Altair]

anubis said:

Come on now... this is rethoric. What do you want me to do ? Tell you about the algorithmic developments of the last years ?

I want you to realize that rasterization has never had such fundamental problems. It seems you don't realize what kind of advantage the simplicity and coherency of the rasterization algorithm gives to the HW implementation. If you take a stab and claim there have been "other things" for Gods sake, back yourself up if you want to claim youself some bit of credibility.

anubis said:

I'm not sure what you are saying though... Rasterizing is more powerful currently ? Has a wider support ? I agree. But what is the point of saying that ? What do you want to tell the world ?
Excuse me if i misinterpreted you but it just sounds like you want to prove that rt tracing is futile. If that's not the case and you just want to point us to the problems at hand that's nice. Rest assured it's being worked on.

I never said RT is futile, but it's just you taking it to personal level and making the conversation black and white. I never said that rasterization was the ultimate rendering algorithm either. We both should realize at this point what are the real advantages and disadvantages of both algorithms AND then work out how to address those problems in both. THAT'S what the mature and constructive conversation is about and I honestly thought we could have that conversation here. There has been some work to modify the raytracing algorithm to be more suitable for stream processors (GPU Gems 2) and I think if you ever want to have well performing raytracing HW, that's what you need to do - modify the fundamental algorithm.

anubis said:

Btw, addressing others as foolish just because they don't share your point of view isn't proving your point one bit.

What are you talking about? If you can't have constructive conversation and get offended because I don't agree with yours, don't start to pull low personal tricks on me.

anubis said:

http://www.openrt.de...otes/course.php
The sixth talk on that page is about dynamic scenes and animation.

I'll check that out. I think it was actually one of the RT courses I attended.

Cheers, Altair

[NomadRock]

Renderman actually doesnt do rasterization or ray tracing it's just an interface. Pixar's implementation uses Reyes which origionally was made to "overcome the speed and memory limitations of photorealistic algorithms, such as ray tracing, in use at the time." This from Wikipidea they also say that nowadays "versions also include ray tracing and global illumination features"

[Goz]

NomadRock said:

Renderman actually doesnt do rasterization or ray tracing it's just an interface. Pixar's implementation uses Reyes which origionally was made to "overcome the speed and memory limitations of photorealistic algorithms, such as ray tracing, in use at the time." This from Wikipidea they also say that nowadays "versions also include ray tracing and global illumination features"

So it does :) Surprises me, tbh ... most of the rendering looks very rasterised (though i openly admit RT and Rasterisation can look identical (such a shame so few ppl do so ... its like the plastic look of all the specularly bump mapped games out there!)

TBH, though, any decent ray tracer does its first pass using rasterising anyway ... you store an ID buffer identifying what polygon is hit and pass it through a rasteriser. You then read back that ID Buffer and perform second passes over the geometry once the rasteriser has performed the visibility detection ... Far far cheaper with modern (and for that matter much older) technology :)

[davepermen]

actually, if you do GI and such with your raytracer, primary rays are only a small part (and constant, while all other can scale depending on the quality you want).. thus, in any raytracers other than witted, using rastericing for first-hits doesn't give much, often not worth the additional effort (espencially if a lot of the geometry isn't simple triangular meshes, but volumetric stuff, pointsamples, etc.. or higherorder (yes, you could tesselate..)).

anyways, for realtime raytracers that don't have much stuff reflecting/refracting, it definitely takes away a bit.. but if you think of a scene with say 5 lights, you have one primary and 5 shadow rays per pixel.. so only one 6th of the whole can get speed up. yes thats a bit, but it does only give some percent.. not a "wow, i speed up by 2x, or 4x or something..".

[musawirali]

Real-time physically based caustics running completely on the GPU:



with light dispersion:



more pictures visit project page: http://graphics.cs.ucf.edu/caustics

[zavie]

Very fancy! *_*

[Alex]

The original question is quite interesting. Sadly the thread is flooded with a big and rather pointless discussion between a few members that discuss their knowledge (or the absense there of) of raytracing. I stoped somewhere on page 3. Is there anything interesting after page 3? Can the pointless discussion be moved to another topic please?

I agree that in terms of image quality GI (or a better approximation of it) will be an importand step forward. The bigger problem I see comeing is the amount of data an engine needs to handle to create an even more realistic world. We will need ever more detailed objects with more detailed surface description (among other properties for physics etc). Already artists outweight programmers in most game development teams.
The next importand thing (IMHO) is to start using procedural geometry and surface descriptions that can be extracted to full geomtry+surface data by the hardware to save storing all the tris or what ever in vidram. Objects could probably be rotated and moved around as procedural rather than a tesselated object with that many thousand verts.
I mean how many gigs of ram do we want to put on our gfx cards before we realize it's never gonna be enough?

Alex

[anubis]

If you check the dates you will see that the thread got resurrected several times and is in fact a year old, so maybe that explains why there are strange topic jumps.

[Alex]

Indeed. Still I'd be interested to hear more opinions on this topic (as originally started in the first post)..so anyone?

Alex

[Kenneth Gorking]

Alex said:

Indeed. Still I'd be interested to hear more opinions on this topic (as originally started in the first post)..so anyone?

Alex

I read an article on ATI's site the other day, on the subject you mentioned:

http://www.ati.com/d...plification.pdf

[zavie]

Alex said:

Indeed. Still I'd be interested to hear more opinions on this topic (as originally started in the first post)..so anyone?

Just a little point. :-)
Ken Perlin has patented a hardware approach to his famous noise. So this could be another step toward real-time raytracing.