Next gen lighting technologies - voxelised, traced, and everything else *spawn*

Discussion in 'Rendering Technology and APIs' started by Scott_Arm, Aug 21, 2018.

  1. trinibwoy

    trinibwoy Meh
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    Trading off one set of hacks for a better set of hacks I suppose.
     
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  2. Ike Turner

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    Since Ray Tracing isn't all about graphics...
    Valve has finally announced the availability of Steam Audio Radeon Rays support in the Beta 15
    https://steamcommunity.com/games/596420/announcements/detail/1681419156989664451

    More discussion in the Advanced Audio Technologies (HRTF, Dolby Atmos, etc) thread here: https://forum.beyond3d.com/threads/...logies-hrtf-dolby-atmos-etc-echo.58309/page-5
     
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  3. Graham

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    This sort of sums up why I feel ray tracing just isn't a good fit for real-time (yet).

    It's just too precise. Real-time graphics are a trade-off of using approximations for performance. You can always be more accurate, but typically the cost for quality curve can get pretty frightening. Which is why I'm a big believer in spacial approximations like voxelization and signed distance fields (SDFs). They can't represent the ground truth, but when you don't have the performance to get to ground truth anyway you might as well choose an approximation that gets you as close as possible for your budget.

    Ray tracing, and variants of, are our best method of getting to ground truth but are arguably the slowest way of getting there - they just get further than other techniques given enough time. Time we don't have.

    My understanding is claybook is SDF based, so their ray performance shows. They made good tradeoffs for their needs.


    I look at the battlefield demo, and while yes it's very impressive I still see the shortcomings very strongly. They clearly have *massively* cut back the complexity of the scene representation for the ray traced environment - you can see it in the dramatically lower detail in the reflections showing the buildings, the first car being the only one creating a reflection (it's underside appears to have been removed, structurally it looks to have been simplified a lot, see the headlight artifacts) - even the tram appears to have had most of it's interior removed, etc. The lighting for the ray samples also appears drastically simplified (presumably using a very simple forward shading path).

    What this says to me is that in order to get acceptable performance they had to really gut their scene complexity. I don't find this surprising at all - but it comes back to way I said earlier, it's too precise. This reduction becomes strongly visible. Would a voxel based representation have been a better fit? Trading ultimate precision for a closer overall match to the world structure (Just lower fidelity)? Would that then allow them to unify their diffuse and specular? - the ray traced reflections being quite a jarring mismatch to the non-traced diffuse...

    Would a better tradeoffs have been to have worse results for these ultra shiny/smooth surfaces, but more accurate results from more common glossy and diffuse surfaces? I would personally make that trade-off.

    I get the impression they are doing something to prevent self intersection with the simplified scene too, which may be making things look a little off. Say, projecting the ray start position in screen space forward from the high res on to the lower complexity scene's depth. Just a guess... But I think that's why some of the contoured reflective surfaces look... Odd...

    I don't want to take away how impressive it still is. I just don't think it's the right solution.

    It's all very interesting tech, but it's just not there in my mind. Once we have 50/rpp/frame capability I think then we'll see a larger shift to using rays for things like shadows - where performance of rays becomes worth the trade-off for increased quality. But I don't see larger scale adoption (diffuse, glossy, etc) until we're at ~500/rpp/frame - and that's a *long* way off. Let alone the how to deal with scenes that have significant depth or movement complexity (dense foliage, open world, streaming, etc).


    In the mean time I see a few games experimenting with small scale uses but ultimately I think most will fall back to tried and true methods when people realize the performance tradeoffs just aren't there, instead using RT hardware for more non-graphics uses. Things like offloading AI visibility etc. For visuals I see cone tracing and variants of being far more prevalent.

    Of course I could be totally wrong :mrgreen:
     
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  4. imerso

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    Yes, but still on a very controlled environment. The guy hand tuned the hell out of the scene, amount of visible polys and viewpoints to reach 30fps.

    Please note that I love that prod as much as everyone else, it's pure art and of extreme quality, but still, imho not a direct comparison to DXR/RTX.
     
  5. zed

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    note also all the physics etc prolly aint happening, everything will of been calculated beforehand eg
    time 1.34
    - list of polygons visible at which positions, which polygons are reflected from these polygons etc
    which really saves CPU/GPU work

    compare this to a game, where anything could happen at time 1.34
     
  6. Ike Turner

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    Quick cross post from the Next-Gen console HW prediction thread in case some don't go there:

    Regarding the debate around general-purpose compute vs dedicated "fixed-function" HW for RT here's Microsoft's stance on it:

    https://blogs.msdn.microsoft.com/directx/2018/03/19/announcing-microsoft-directx-raytracing/

    "You may have noticed that DXR does not introduce a new GPU engine to go alongside DX12’s existing Graphics and Compute engines. This is intentional – DXR workloads can be run on either of DX12’s existing engines. The primary reason for this is that, fundamentally, DXR is a compute-like workload. It does not require complex state such as output merger blend modes or input assembler vertex layouts. A secondary reason, however, is that representing DXR as a compute-like workload is aligned to what we see as the future of graphics, namely that hardware will be increasingly general-purpose, and eventually most fixed-function units will be replaced by HLSL code. "


    So yeah, Turing's RT Cores go against' s Microsoft's DXR vision. But this just strengthens my belief that Turing is principally a Pro grade GPU aimed and conquering the Deep Learning and most-importantly (compared to Volta) the CGI industry by totally replacing CPU based render farms in the long run (which is IMO the right way to go and I fully support NVidia in this endeavour).

    EDIT: More DXR stuff

    All RT operations go through DXR and are cross vendor/GPU arch compatible but on Turing GPUs some of the calls are automatically translated to OptiX (CUDA) through the driver and accelerated buy the (still mysterious) RT Cores.

    Here's an example with ChaosGroup (VRay) project Lavina's real-time RT renderer which also interestingly doesn't use OptiX AI denoising but their own cross vendor AI denoising solution (VRay Next support both for production rendering):


    https://www.chaosgroup.com/blog/ray-traced-tendering-accelerates-to-real-time-with-project-lavina
     
    #126 Ike Turner, Aug 26, 2018
    Last edited: Aug 26, 2018
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  7. Jupiter

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    In my opinion, screen space reflections have for example really annoying artefact in games. What does UHD help me if I can see the same mistakes for 15 years. At some point I get fed up with this level of graphics and I want something fresh. How to solve the problem with screen space artifacts of SSRs etc. without using raytracing? The question is how to get raytracing as performant to use it in real time. The fact that one has to make precision cuts is logical. The ray is started by the developer with an offset and if it does not hit one object it's not a film quality path tracer but still several leagues above any sreen space effect. In the end it is up to the developer which trade-off in terms of speed and quality they want to have.

    This is subjective and the same argument can be made for any effect. In the one hand some will say if UHD with 240fps are not possible they will turn raytracing off while on the other hand some people prefer to see the nice reflections… Turing is the first GPU generation of this kind and Battlefield etc. are the earliest of those raytracing implementations in games and I think it can only get better and better.
     
    #127 Jupiter, Aug 26, 2018
    Last edited: Aug 26, 2018
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  8. DavidGraham

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    These cutbacks are present normally in any Battlefield game, objects are not usually detailed unless they are controlled by the player. This is a 64 player mayhem multiplayer after all, cutbacks are needed everywhere. You can see the same in Battlefield 1 as well.
     
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  9. Lalaland

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    Cross posting this from the impact of RT on consoles thread as I figured folks here might be interested too.

    Speaking of the Quadro market, ChaosGroup the makers of V-Ray span up a demo named Project Lavina using RTX now while they are not making any commitment to releasing it into production they will be taking the lessons back for V-Ray GPU and may down the line release it. Haven't seen any others yet
    https://www.chaosgroup.com/blog/ray-traced-tendering-accelerates-to-real-time-with-project-lavina

    I do wonder if we'll see any other serious rendering products offer this, I wouldn't expect them to ever reach final production quality but higher quality previews are always welcome
     
  10. Ike Turner

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    I cross posted it here just 2 message up ;)
     
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  11. Lalaland

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    I am the dumb! I'll leave my post as a warning to others to read the thread properly:lol:
     
  12. OCASM

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    Octane is RTX accelerated as well.

     
    #132 OCASM, Aug 28, 2018
    Last edited: Aug 28, 2018
  13. 3dilettante

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    I'm not seeing much detail as to the particulars, but some counter-pressures to expanding the scope of the programmable units may be the way Nvidia's trying to fit more resources or performance into a transistor and power budget that has not been improved by going to 7nm. A dedicated hardware path can be added with limited impact to die size and power consumption. The scheduler and data paths dedicated to the more fully-featured units are already expensive and optimized towards a granularity that earlier research showed problems with divergence.
    In this scenario, the programmable paths already have significant overheads to cover their broader use cases, and burdening them more would increase area/power/delay while at the same time using them less efficiently.

    In terms of risk management, something as speculative as the RT hardware might have been better of as a separate and concurrent development project that was less likely to be delayed by the standard units' own design projects/potential cancellations and vice versa. Having multiple hardware variations come out even within a family due to the timing of a specific tech's maturation relative to when specific GPUs were finalized occurred with double-rate FP16.

    Perhaps at a later time with more silicon to play with and better evaluation on how the functionality can be more seamlessly carried out by the main SM units, that might change.

    Other factors that I am curious about are whether there's something to Nvidia's implementation that makes the payoff from running in the SIMDs less important. Some of the workarounds for BVH traversal and testing use persistent threads to process ray packets, which means longer-lived threads whose relationship to primitives is the reverse of pixel or vertex work. Traversal sounds memory-limited, which may be why there are multiple ALU and tensor subcores, but the newer streaming memory unit of the SM is 1:1 with the TEX and RT blocks. There was a tweet about the RT core being a hardware path that scheduled work and L0 buffers for the BVH work, which may be a similar sequencer-heavy process to how texturing can generate multiple real memory addresses.
    The allocation of L0 cache storage might point to a similarity with another form of special-purpose hardware whose job is to follow indirection through hierarchical tables to reach a leaf node or array, a page table walker and hierarchy of TLB and intermediate translation caches.
    A pipeline like that can try to coalesce requests from across various warps and try to extract locality without bogging down their schedulers, registers, and instruction caches. Specific features to Nvidia's implementation may encode shortcuts or other methods for speeding up traversal or freeing/updating the hierarchy. The depth of the hierarchy and the mapping aren't as straightforward, but the concept of having a hardware unit able to navigate it is well-understood and there may be parallels in managing updates to the BVH somewhat more efficiently as there are for maintaining and updating the page table structures.

    Having hardware for that isn't strictly necessary, but even so having it has proven compelling for many architectures.
     
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  14. SeeNoWeevil

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    You've got to see the funny side of GPU vendors, display manufacturers and gamers going full steam ahead on the 4K hype train and the moment we get GPUs powerful enough to comfortably do 4k60, Nvidia announce raytraced 1080p60 is the new hotness. Like 4K was just something to throw new GPUs at until they figured out real-time raytracing. I can kinda see why there's such a backlash. The people buying high-end GPUs also probably bought higher res/refresh displays because that was the obvious direction of a number of industries. Are gamers going to find themselves in a 4K *or* raytracing situation?
     
  15. milk

    milk Like Verified
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    Of course, otherwise what will they sell you 3080s on?
     
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  16. Shifty Geezer

    Shifty Geezer uber-Troll!
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    They've always been in a "higher quality or higher resolution" situation - that's why there are settings for gamers to adjust to pick which compromise they prefer. This is no different to having 1 or 6 shadow casting lights on your Ti4600 back in the day.
     
  17. OCASM

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    The last decade has spoiled gamers with console ports. Now that an actual high-cost, high-end feature shows up many of them are losing their minds :lol:
     
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  18. London-boy

    London-boy Shifty's daddy
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    Wait how is a picture of my house on there????? I’m scared now.

    Edit. Never mind!
     
    #138 London-boy, Sep 6, 2018
    Last edited: Sep 7, 2018
  19. trinibwoy

    trinibwoy Meh
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    http://boostclock.com/show/000219/gpu-rendering-nv-fermat-gtx980ti-gtx1080-gtx1080ti-titanv.html

    Wonder why the 980Ti is consistently faster than the 1080, up to 25% in one scene.
     
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  20. OCASM

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