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Ray Tracing Is No New Thing

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Re: Ray Tracing Is No New Thing

#11

Post by toolslive »

rollulus wrote: post #7

I'd say that it is rather obvious that ray tracing is not a new thing, since it is simulates how light physically behaves. I consider this 3d rendering as a spectrum: rasterization requires little computation but has little to do with physics. Ray tracing is what requires a lot of computation and has everything to do with physics. Somewhere in between are hybrid methods: rasterization with ray tracing components adde…

> since it is simulates how light physically behaves.

I think ray tracing is at best an ad-hoc model for light that produces nice results, but physically based it isn't.

Re: Ray Tracing Is No New Thing

#12

Post by mbel »

rollulus wrote: post #7

I'd say that it is rather obvious that ray tracing is not a new thing, since it is simulates how light physically behaves. I consider this 3d rendering as a spectrum: rasterization requires little computation but has little to do with physics. Ray tracing is what requires a lot of computation and has everything to do with physics. Somewhere in between are hybrid methods: rasterization with ray tracing components adde…

> For instance, pure rasterization cannot do shadows.

Well... the technique that you describe (shadow mapping) is actually pure rasterization it just requires more than one rasterization pass. This also ignores the fact that there are other techniques for getting shadows in rasterizing renderers (stencil volumes and other stuff that is rather considered historical today).

I get your point that rasterization doesn't support shadows "naturally" like ray tracing, but in my opinion your wording and the example is rather unfortunate. The same goes for reflections, I would say SSS or caustics probably are better examples since they are really only done with techniques based on ray tracing.

Re: Ray Tracing Is No New Thing

#13

Post by EpicEng »

arayh wrote: post #5

Gamers have long been clammering about how they can't wait until in-game graphics match those of pre-rendered cinematics (that said, a lot of cinematics these days are no longer pre-rendered). Ray tracing is such an expensive operation. According to this quora, it took 29 hours to render a single frame of "Monsters University": https://www.quora.com/How-long-does-it-take-to-render-a-Pixa... We're probably nowhere clo…

>Gamers have long been clammering about how they can't wait until in-game graphics match those of pre-rendered cinematics

Well, they do, you just have to look back X years depending on your criteria. Look at modern in game graphics v PSX cinematics for instance. It's not even close.

Re: Ray Tracing Is No New Thing

#14

Post by MisterTea »

learc83 wrote: post #6
arayh wrote: post #5

Gamers have long been clammering about how they can't wait until in-game graphics match those of pre-rendered cinematics (that said, a lot of cinematics these days are no longer pre-rendered). Ray tracing is such an expensive operation. According to this quora, it took 29 hours to render a single frame of "Monsters University": https://www.quora.com/How-long-does-it-take-to-render-a-Pixa... We're probably nowhere clo…

That's because it's a moving goalpost. Pixar keeps increasing the quality to take advantage of faster hardware and better algorithms. We'll never be close to getting today's real-time Pixar-quality until Pixar rendering is good enough that they stop meaningfully improving it. What we can have is yesterday's Pixar quality rendering in-game.

That should be a new goal post: can it render a pixar film in real-time. e.g. Do we have a Toy Story capable card yet?

(Note: I know offline rendering and real-time raster rendering we use in GPU's are completely different methods. But there is a point where the raster trickery can catch up and match the offline stuff.)

Re: Ray Tracing Is No New Thing

#15

Post by octachron »

rollulus wrote: post #7

I'd say that it is rather obvious that ray tracing is not a new thing, since it is simulates how light physically behaves. I consider this 3d rendering as a spectrum: rasterization requires little computation but has little to do with physics. Ray tracing is what requires a lot of computation and has everything to do with physics. Somewhere in between are hybrid methods: rasterization with ray tracing components adde…

Even ray tracing does not capture all physics of electromagnetism and only works at the level of geometrical optics: any effect, like diffraction or iridescence, that arises due to the wave-like nature of light still need to be implemented in ad-hoc way in a ray tracing algorithm. But fully simulating Maxwell's equations (or QFT) to keep track of those minor effects would be insanely expansive.

Re: Ray Tracing Is No New Thing

#16

Post by twtw »

bitL wrote: post #3

Can someone from AMD/NVidia please jump in and explain the difference between Radeon Rays (2016?) and RTX (2018)? Thanks!

Radeon Rays is more comparable to OptiX (2009), in that both are GPU accelerated ray tracing libraries. RTX (2018) differs in that it uses special purpose ray tracing units on the GPU, rather than running only on the SMs/CUs.

Re: Ray Tracing Is No New Thing

#17

Post by swerner »

rollulus wrote: post #7

I'd say that it is rather obvious that ray tracing is not a new thing, since it is simulates how light physically behaves. I consider this 3d rendering as a spectrum: rasterization requires little computation but has little to do with physics. Ray tracing is what requires a lot of computation and has everything to do with physics. Somewhere in between are hybrid methods: rasterization with ray tracing components adde…

It's much simpler than that: Both rasterisation and ray tracing are methods to solve visibility. The main difference is that one answers the question "given a primitive, what pixels does it overlap?", the other "given a pixel, what primitives does it overlap?"

Light transport, shading, shadowing are all just implemented on top and not a direct result of the visibility calculation.

Re: Ray Tracing Is No New Thing

#18

Post by mattnewport »

SketchySeaBeast wrote: post #10
mattnewport wrote: post #8

Earlier quoted context omitted.

Dedicated hardware to accelerate BVH traversal and ray triangle intersections. Previous GPU accelerated ray tracing implementations have just used existing hardware for programmable shaders for these but that hardware isn't ideally suited to the task.

So in that case is this going to be a "G-Sync"/"Freesync" or "Gameworks"/"No, I like my framerates" thing? If developers begin supporting the RTX hardware is there a way AMD can get on board, or is this another one of NVidia's patented industry hurting moves?

For games most will access the functionality via the new DirectX ray tracing APIs (or perhaps the Vulkan equivalent in the future) so there's nothing stopping AMD or Intel from adding hardware to accelerate those APIs too.

Re: Ray Tracing Is No New Thing

#19

Post by twtw »

SketchySeaBeast wrote: post #10
mattnewport wrote: post #8

Earlier quoted context omitted.

Dedicated hardware to accelerate BVH traversal and ray triangle intersections. Previous GPU accelerated ray tracing implementations have just used existing hardware for programmable shaders for these but that hardware isn't ideally suited to the task.

So in that case is this going to be a "G-Sync"/"Freesync" or "Gameworks"/"No, I like my framerates" thing? If developers begin supporting the RTX hardware is there a way AMD can get on board, or is this another one of NVidia's patented industry hurting moves?

I can't answer the question, but I'm curious how you think NVIDIA should have introduced real time raytracing to the industry? They can make it proprietary at the API level, or proprietary at the ISA level, but at some point you're stuck with the fact that their hardware can do something AMD's cannot.

Is it industry hurting to make the GPU they sell have any exposed new capability, other than making the same old thing slightly faster?

Re: Ray Tracing Is No New Thing

#20

Post by maeln »

SketchySeaBeast wrote: post #10
mattnewport wrote: post #8

Earlier quoted context omitted.

Dedicated hardware to accelerate BVH traversal and ray triangle intersections. Previous GPU accelerated ray tracing implementations have just used existing hardware for programmable shaders for these but that hardware isn't ideally suited to the task.

So in that case is this going to be a "G-Sync"/"Freesync" or "Gameworks"/"No, I like my framerates" thing? If developers begin supporting the RTX hardware is there a way AMD can get on board, or is this another one of NVidia's patented industry hurting moves?

As far as I know, both Vulkan (with extensions, for nvidia VK_NV_raytacing) and DirectX (with DXR) have ray-tracing capabilities in their standard. Their shouldn't be any patent that deny AMD from providing an implementation in their drivers.
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