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Ray Tracing

ElectricMucus
Explorer
What do you guys think about ray tracing?

I think the game industry should make the transition from rasterisation based techniques to ray tracing techniques simultaneous to the adoption of VR. There is tons of research on novel approaches on countless different global illumination techniques and much on acceleration techniques to make it more efficient.

There is just so much stuff we can't do with rasterisation based rendering and so much more flexibility in ray tracing based rendering that it might be the time to start doing the switch.
Think about lens correction which now requires oversampling, the pentile display which is oversampled at native resolution for red and blue, time shift which can't render occlusion differences. All of those things are possible to do in a ray tracing engine with negligible overhead completely elegant.

There is also the call for immersion which simply won't be there without plausible lightning and depth cues.


Ray tracing in gaming is facing a bit of a chicken and egg problem: As long as graphic cards do not accelerate it efficiently game developers won't use it and as long as no game engine utilizes it graphic card manufacturers won't bake acceleration into the hardware.
IMHO the first step is up to the game development community, because that's how historically it worked (see quake 1).
11 REPLIES 11

jokamo
Honored Guest
i think first we're gonna need to handle the requirements of VR first before we move onto ray tracing. Its still an incredibly hard task even for high end pc's!

Miffyli
Honored Guest

cubytes
Protege
hmmm fascinating i just researched ray tracing



ray tracing and photon mapping = high fidelity graphical awesomeness to the max like whoa!

but from what i gather processing that much data in real time is very computational heavy and would require a beast of a machine to pull off.

i just learned about the 'rendering equation' too no wonder you need rending farms....

ray tracing in particular is so counter intuitive too, but yet it works extremely well as far as naturally expressing photo realistic behavior of light. imagine coming up with the idea of casting or tracing rays of light outwards from the camera itself....genius.

although for VR i think performance is a huge issue more so then high end graphical fidelity

ElectricMucus
Explorer
"jokamo" wrote:
i think first we're gonna need to handle the requirements of VR first before we move onto ray tracing. Its still an incredibly hard task even for high end pc's!

What I am basically saying is because ray tracing can do the additional VR requirements elegantly and with practically zero performance loss the gap between the raster engines becomes smaller.
And I think it is small enough.

Ray tracing in a sense is a bit of a weasel term also. Rigorously it's just the technique of shooting out a straight line of every pixel and reflecting it until it hit a light source. But in common terms that also means path tracing, metropolis light transport, cone tracing, radiosity, and countless variations and improvements thereof.

There is tons of academic research on the subject of global illumination, monte carlo integration, acceleration structures, and also on leveraging gpu power, even with straight shading language. I've read over some papers which archive real time frame-rates with perceptually indistinguishable quality to the physically correct display, others which compromise a little quality to archive a magnitude of speed. There even is one where they can provide guaranteed frame rates. (Think constant 90hz on CV1 no matter what)

"Miffyli" wrote:
Yes, it will be the future most likely. Plus forum user TeraBit tried out raytracing with rift, and it looks promising.

Cool I wasn't aware of that, I will definitely check it out.

What immediately comes to mind is instead of rendering lens distortion every frame, with ray tracing the virtual lens can be rendered through once and then use the stored vectors to directly map to the pixels.

ElectricMucus
Explorer
Oh if you haven't already you should definitely check out this video of John Carmack explaining it.

Spoiler warning:
He thinks it is not quite ready to be used in games... yet. 😉


cubytes
Protege
"ElectricMucus" wrote:
Oh if you haven't already you should definitely check out this video of John Carmack explaining it.

Spoiler warning:
He thinks it is not quite ready to be used in games... yet. 😉




sweet thanks for posting. watching this video right now. really ties into what i was briefly researching when trying to learn about ray tracing and while also thinking about the fundamental physics of light in general.

kojack
MVP
MVP
The PowerVR GR6500 gpu has hardware raytracing. Not just gpgpu style raytracing using shaders or opencl/cuda, but actual hardware dedicated explicitly to ray tracing (while still having a full PowerVR gpu for normal rasterising).
The current version is a mobile gpu that can do 3-5 rays per pixel at 1080p 30Hz. That's not quite what we need for VR, but it's still pretty amazing for a mobile gpu. If they could do a pc version, that could be awesome. Although Imagination Technologies gave up on PC graphics cards many years ago.
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agnu
Honored Guest
conventional ray tracing techniques (like path tracing) can produce very good results, but their computational requirement is huge. Tipically you can achieve much better results at a given frame rate using traditional incremental graphics, with some tricks.

PowerVR GPUs support ray tracing but they are not using them to generate the images, they use a hybrid system. They still render stuff normally, and Ray tracing is only used to create high quality shadows and reflections only. Which is i think a nice use for ray tracing.

Drawing a mesh with shaded triangles + specular lighting, with no reflections/refractions (which we do a lot) are at almost the same quality with incremental and ray tracing techniques, but the ray traced version uses a lot more resources to do that.

even with gpgpus, ray tracing a scene of a game is very hard, not to mention path tracing. GPGPUs may seem to be good for ray tracing, because of the many parallel threads, but in reality the threadgroups must wait a lot at each other, because of the different behavior of the threads.
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DanSchmitt
Explorer
http://www.wolfrt.de => Wolfenstein: Ray Traced
http://blog.qwrt.de => optical distortion compensation using ray tracing