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Carmack Speaks On Ray Tracing, Future id Engines
Posted by
Zonk
on Wed Mar 12, 2008 04:03 PM
from the how-can-you-not-listen-to-the-carmack dept.
from the how-can-you-not-listen-to-the-carmack dept.
Vigile writes "As a matter of principle, when legendary game programmer John Carmack speaks, the entire industry listens. In a recent interview he comments on a multitude of topics starting with information about Intel, their ray tracing research and upcoming Larrabee GPU. Carmack seems to think that Intel's direction using traditional ray tracing methods is not going to work and instead theorizes that using ray casting to traverse a new data structure he is developing is the best course of action. The 'sparse voxel octree' that Carmack discusses would allow for 'unique geometry down to the equivalent of the texel across everything.' He goes on to discuss other topics like the hardware necessary to efficiently process his new data structure, translation to consoles, multi-GPU PC gaming and even the world of hardware physics."
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"How will ray tracing for games hit the market? Many people expect it to be a smooth transition - raster only to raster plus ray tracing combined, transitioning to completely ray traced eventually. They think that in the early stages, most of the image would be still rasterized and ray tracing would be used sparingly, only in some small areas such as on a reflecting sphere. It is a nice thought and reflects what has happened so far in the development of graphics cards. The only problem is: Technically it makes no sense."
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"Moore's Law works in favor of Ray-Tracing, because it assures us that computers will get faster - much faster - while monitor resolutions will grow at a much slower pace. As computational capabilities outgrow computational requirements, the quality of rendering Ray-Tracing in real time will improve, and developers will have an opportunity to do more than ever before. We believe that with Ray-Tracing, developers will have an opportunity to deliver more content in less time, because when you render things in a physically correct environment, you can achieve high levels of quality very quickly, and with an engine that is scalable from the Ultra-Mobile to the Ultra-Powerful, Ray-Tracing may become a very popular technology in the upcoming years."
[+]
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There is a great disturbance in the source... (Score:5, Funny)
Re:There is a great disturbance in the source... (Score:5, Interesting)
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Re:There is a great disturbance in the source... (Score:5, Informative)
Tim.
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Re:There is a great disturbance in the source... (Score:5, Informative)
And even so, while tracing either photons or eye rays may be the most feasible method at the moment, it is by no mean the only way to solve the rendering equation, nor any kind of theoretical best.
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Re:There is a great disturbance in the source... (Score:5, Funny)
When that happens, will it also become possible to wield a flashlight and a shotgun at the same time? Or is there some kind of fundamental law against that, like how you can't know the position and velocity of a particle at the same time?
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Re:There is a great disturbance in the source... (Score:5, Interesting)
Everything light does is a combination of reflections and refractions (shadows are an artifact of those).
So, yeah, what you are in effect saying is that raytracing only provides realistic rendering of things that light actually does.
Color bleeding and caustics are effects of reflection, subsurface scattering is reflection and refraction, depth of field is refraction (through a lens between the viewpoint and the image). Now, its true, that there are shortcuts that provide tolerable approximations of those effects faster than actually tracing rays in most cases, and that even static raytracers often prefer those to what would be necessary to do those effects through raytracing alone. Its also true that some real effects, to do well with raytracing, would require shooting separate rays for different wavelengths of light, which while conceptually possible (and I think some very specialized systems have been made which do this), is probably utterly impractical for realtime systems for the forseeable future (this is a lot bigger load increase than anti-aliasing would be.)
But as for realism (but not necessarily practicality, especially in a realtime setting), I think raytracing still, ultimately, wins on all of those.
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Re:There is a great disturbance in the source... (Score:5, Informative)
Except the double-slit experiment. It's based on the fact that light has wavefront qualities, while ray tracing treats it as particles.
I also strongly doubt that the discreet ray approach will ever produce very good global illumination, since the number of rays bouncing between surfaces quickly grows towards infinite as the desired accuracy grows.
You'd need to do "wavefront racing" to fix these, and I for one have no idea how to do this - solve the quantum field equations for each particle in the scene after inventing the Grand Unified Theory ?-)
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How does it play with Physics? (Score:5, Interesting)
The problem with this is that we are moving more and more towards interactive environments where everything from the ground to the flowerpots are breakable, bendable or movable. It doesn't sound like this new system will play very nice with physics intensive or highly interactive environments. Now, i could be completely wrong. He doesn't address the point directly. But it is still a point for concern.
Re:How does it play with Physics? (Score:5, Insightful)
A (longdistancetypedheretoavoidlamenessfilter) B
A non-tree method would just calculate all the interactions: A-B, A-C, B-C. But you can group B+C together when calculating their interaction with A because, at that distance, the result for (B+C)-A is the same as the result for B-A + C-A. Then the interaction between B & C must be calculated separately. So you've (even in this tiny example) reduced your calculation from 3 to 2.
And, of course, all the 'voxels' between A & B/C that are empty need not be considered at all. If you'd set it up as an NxNxN voxel cube, you'd be wasting time on calculating empty voxels between the occupied items.
So if you want realistic interactive environments, sparse voxel octtrees are the way to go-- you pump all the calculation time into the parts where it matters, and let the other stuff be 'smoothed' when such smoothing is indistinguishable from rounding error.
Typically, you can traverse the tree for a given error percentage, e.g. 'walk the tree and do interactions preserving 99% energy conservation' or similar. So your have predictable error, as well, despite being able to use arbitrary geometries and spacing for your elements.
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Re:How does it play with Physics? (Score:5, Insightful)
Yea. Because interactivity trumps photorealism for every single possible type of game. Oh wait, that's false.
You sound like the people who said that StarCraft was crap because sprites were outdated junk and every good game (like Total Annihilation) had already moved to 3D. Different engineers will make different design choices for different applications, and there is no total order of correctness among a single class of design choice.
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Limited graphics (Score:5, Funny)
The Most Telling Quote.... (Score:5, Insightful)
Yet, when I play a game, I'll admit, I'm not playing glaring attention to these faults. The last thing that really bothered me in games was 16-bit color banding and I haven't seen any of that in, oh, like 3 or 4 years.
The gamer side of me agrees with Carmack on things looking cool who cares if it's wrong, the geek side of me is angry and demands it be pixel-accurate.
Re:So, (Score:5, Funny)
Don't feel bad, he has probably never heard of you either.
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Re:So, (Score:5, Informative)
You've never heard of any of those? the guys you mention might not even be in gaming if it weren't for Carmack and John Romero.
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Re:So, (Score:5, Informative)
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Re:So, (Score:5, Insightful)
George Washington is pretty legendary, but we don't have a George Washington's America, do we? The name is irrelevant. How could the guy who basically invented the First Person Shooter not be legendary? When it first came out, the original Wolfenstein was the most highly optimized game I'd ever played. I still remember thinking it wouldn't run on my slow-ass computer, and being blown away when it ran fast as can be.
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Re:Stunning! (Score:5, Insightful)
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Re:Stunning! (Score:5, Insightful)
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Re:Stunning! (Score:5, Insightful)
Commenting on the fact that it is unsurprising that someone working on a different technique favors that technique over raytracing is not throwing anything out.
Its not a comment either way on the merits.
Were I to comment on the merits, I would point out that his position is both fairly obviously correct (in that sparse voxel octrees or something quite like them is almost beyond question the key to raytracing that's useful for reasonable quality in realtime), and entirely incorrect in his characterization of what everyone else is pushing: he pretends that "everyone" is pushing the most naive, brute force approach to raytracing, in which you don't use any kind of bounding volume structure and just do intersection tests against triangles. I've seen literally no recommendations that do that: almost all involve some form of bounding volume heirarchy, and sparse voxel octrees are just one instance of that (perhaps a fairly ideal one, and that's great). (Also, raytracing isn't limited to triangles, although most performance comparisons of raytracing to raster-based rendering methods use models constructed from triangles because it allows you to compare same-model performance of the different mechanisms; raytracing engines, however, don't generally need to decomposed curved objects into triangle-based approximations to render them in the first place, although this can sometimes be more efficient.)
TFS further misleads by suggesting that Carmack is proposing an alternative to raytracing, when really what he is proposing is a particular approach to raytracing, and, particularly, a particular approach in one well-known problem area in raytracing to which there are currently a whole array of approaches. And his focus on what he wants to get out of raytracing is a little different. But, essentially, his piece, while there are some potentially good criticisms on some particular aspects of and arguments for Intel's specific approach to raytrace, is in accord with (not opposed to) the general idea that raytracing techniques are going to be increasingly important in gaming.
Is that enough "on the merits" for you?
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Re:Stunning! (Score:5, Interesting)
Give me a little credit here. I am not suggesting that everyone blindly intersects rays with a huge list of triangles. That would be absurd, and I assumed everyone understood that. What you might have missed is that I'm not proposing a sparse voxel octree as some form of bounding hierarchy to reduce intersection tests against triangles, I am proposing that it REPLACE hierarchies of triangles or other primitives for some data sets, and this brings about significant improvements (data size) that you wouldn't have with even infinitely fast conventional ray tracing. I'm also not trying to say that this is some novel brainstorm of mine, but I have some practical experience with the direction, and I think it has promise.
One of my major points is that this is all still theoretical. I don't know what is going to be the right architecture for next gen systems. Neither do you, or Intel, Nvidia, Microsoft, Sony, or Nintendo. If I had to place a bet, it is that rasterization will still be dominant, but it is a Good Thing to have lots of people doing research into various alternatives. All the players have their own agendas, but we will all know the big win when we see it.
John Carmack
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Re:Stunning! (Score:5, Funny)
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Re:How about.... (Score:5, Insightful)
Its his job, and im pretty sure his passion to think about stuff like this.
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Re:Right... (Score:5, Insightful)
Plusses:
- One of the primary fathers of the FPS genre.
- Wolfenstien 3D
- Doom
- Quake 1
- Quake 2
- Quake 3
- Endless articles and commentary on the field
- A shitload of stuff I'm forgetting
Minusses:- "Thought multiplicative lighting was the way to go, rather than dealing with the performance hit of additive lighting in Quake 3."
Conclusion: Carmack sucks!I mean, seriously, what's your point? The man's not actually a God so we shouldn't listen to him? Is there somebody more experienced I should prefer to listen to? Is "n3tcat" the handle for somebody with thirty years experience in first-person shooter engines or something?
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Re:Right... (Score:5, Interesting)
You sound like someone that's had the same thought every serious modder/engine-licensee has ever had; "if they could have just included/modified this ONE feature, my game would be feasible/better."
Yet you haven't encountered that phrase enough times to appreciate the fact that engine developers have to draw a performance line somewhere. Your desired feature just happened to be on the wrong side of that line.
Further, engine-developers of John Carmack's caliber would (I promise you this) love to have supported every feature you've ever thought of (and more). John Carmack's always been on the cutting edge, usually refining it. He sometimes makes decisions that are a matter of taste that you can feel free to disagree with him on, but that particular feature wasn't one of them.
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Re:So... what this tells me... (Score:5, Insightful)
Meanwhile the rest of us have been enjoying these articles immensely because we get to obtain some insight about what each of the major players are thinking in regards to Real-Time Raytracing. The great thing about obtaining insight from others is that you can then use your newfound insight to come to your own conclusions.
If you're simply looking for a consensus from the industry, don't expect one for a long while. The concept won't entirely be accepted until someone goes out there and proves it out. Just like high-quality 3D graphics were thought to be too slow on the PC. Until game creators proved out a few different methods to make them usable, that is. (Starting with Wing Commander, moving to Wolf-3D, Doom, Duke 3D, and eventually Quake. After that, the industry said, "Welp, we better make some hardware for this." And thus 3DFX was born.
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