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Ray Tracing Overview - Unreal Engine 4.22 Preview

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  • replied
    Originally posted by Stephen Ellis View Post

    Raytracing does not support Landscapes currently
    Hello, I find that ray tracing has become very bad since Priview 5; by Priview 6, RT AO is almost invalid, even close to SSAO, and it is totally impossible to calculate scene AO correctly; but it seems that in Priview 7, there is still no effective way to fix this problem. Will it be fixed in the next preview or official version?

    Another question is, since Ladnscape and Foliage are not supported in 4.22, how can we get a hybrid rendering scheme? For example, open both RT Shadow and CSM Shadow to illuminate the scene, while CSM Shadow to illuminate Landscape and Foliage; if not, it means that RT Shadow can hardly be applied to outdoor or large-scale scenes in version 4.22.

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  • replied
    Originally posted by lobachevscki View Post
    is raytracing supporting terrains in this release?
    Raytracing does not support Landscapes currently

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  • replied
    Hi!

    Nice thread.

    Didnt check everything written here, so i dont know if it is already mentioned, but i cant confirm this information: is raytracing supporting terrains in this release?

    Thanks!

    Leave a comment:


  • replied
    Originally posted by smashems View Post
    After enabling Ray Tracing + Skincache for a project, I cannot open that project back up again; the editor crashes when trying to launch it.
    This is a known issue on Preview 6. The fix is to disable launching the editor in dx12 so that it reverts to dx11, and then letting the editor compile shaders with dx11. Then, afterwards, you can restart the editor in dx12 again.

    This issue has been fixed for the next release.

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  • replied
    Hello,

    After enabling Ray Tracing + Skincache for a project, I cannot open that project back up again; the editor crashes when trying to launch it.

    My Specs
    • Windows 10 (Version 1809, Build 17763.379)
    • 2080 Ti (Driver 418.91)
    The Error

    LoginId:****
    EpicAccountId:****

    Assertion failed: ShaderRef != 0 && *ShaderRef != nullptr [File:\Build\++UE4\Sync\Engine\Source\Runtime\RenderCore\Public\Shader.h] [Line: 1887]

    UE4Editor_Core
    UE4Editor_Core
    UE4Editor_Core
    UE4Editor_Core
    UE4Editor_Engine
    UE4Editor_Engine
    UE4Editor_Engine
    UE4Editor_Engine
    UE4Editor_CoreUObject
    UE4Editor_CoreUObject
    UE4Editor_CoreUObject
    UE4Editor_Engine
    UE4Editor_Engine
    UE4Editor_CoreUObject
    UE4Editor_CoreUObject
    UE4Editor_CoreUObject
    UE4Editor
    UE4Editor
    UE4Editor
    UE4Editor
    UE4Editor
    kernel32
    ntdll

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  • replied
    For Prview 6, the shader must be compiled in DX11 before it can run normally in DX12 mode.

    Moreover, RTAO has a problem in this version. The maximum distance of light in RTAO seems to be very small. Only part of AO can be seen in some detail areas, and this distance is not affected by RTGI. Perhaps it is for independent AO and GI to split part of their content, and then forget to add tracking distance for RTAO? In short, the tracking distance of RTAO becomes very small, even close to SSAO, almost invalid.

    It would be great if RTAO and RTGI could be separated independently. After all, RTAO is more cost-effective than GI in some scenarios.

    It seems that Prview 6 has solved many problems, including the disappearance of translucency and the flicker of Msak material. Looking forward to seeing HISM and Folaige in 4.22, or hybrid rendering solutions (such as CSM + RTShadow complete HISM, Folaige, Mesh, etc.), that's great!
    Last edited by Leo Rakes; 03-21-2019, 09:42 AM.

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  • replied
    Antidamage one thing at a time, I am already glad with shadows and reflections, can't be more happy with all the rest, too many new things at once I guess. Hopefully we will get an even clear view in the next months!

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  • replied
    @nilsonlim DLSS is just a realtime tree lookup of a neural network index for upscaling. It doesn't use all 9 Tflops of the Tensor cores to run the DLSS lookup, and plenty of things Tensor cores are good at run almost as well in CUDA. The only requirement is that the source frame resolution matches the training data, which up until now has been 1440p as the reference and possibly up to 16k as the training data.

    You could conceivably train some high res RTX results against some low res RTX results with a particular feature set to get 4k RTX gaming on a 1080, just not with a source of 1440p. So all the data would need to be retrained. Maybe they could target just the RTX combined results in low res + DLSS and combine it with a high res diffuse scanline layer. Maybe 720p. I'm sure there's a balance that would let you target 60fps.

    Unfortunately with the high cost of training DLSS at the moment we'd need NVidia's cloud DLSS training service available to try it. But I'm sure it's possible and we could even do it in Unreal Engine. The other neat thing about only training your RTX combined buffers is the single set of result might be usable on any game using that method.

    It's worth noting that the AI denoiser is also an implementation of the tech behind DLSS, and you've seen how much that can clean up your image.
    Last edited by Antidamage; 03-20-2019, 05:33 PM.

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  • replied
    do you have any project files for testing ? thx!

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  • replied
    Originally posted by Antidamage View Post
    I'm actually curious as to if it means DLSS will work on Pascal cards. If so, RT isn't entirely infeasible for games that can use DLSS to upsample.
    The DLSS (Deep Learning Super Sampling) feature can only run with Tensor Cores, so it is locked to a hardware feature, and it is not feaseble because what I will show below:

    It can be understood with the slide NVidia showed with the explanation on how strong a Pascal card like GTX 1080TI would need to be to perform a Metro Exodus rendering scene at 60FPS in 1440p with RTX ON and DLSS.


    Click image for larger version  Name:	20190318_231322740x414.png Views:	1 Size:	138.0 KB ID:	1596777

    And also which is the performance distribution in the RTX card to do the job per feature inside the card:

    Click image for larger version  Name:	20190318_2318481030x572.png Views:	1 Size:	106.1 KB ID:	1596778

    So, the RTX cards got RT cores, INT+FLOAT and Tensor Core features that alone sum up 23 + 2 + 9 TFLOPS = 34 TFLOPS equivalent in power, so theoretically a GTX 1080TI is only able to do 10 TFLOPS from the 44 TFLOPS required. Also check in the image the peaks! That is scary!

    To understand what will be delivered, you need to imagine the same scene but without DLSS, which we know will drop the framerates because there would be no performance improvement, so we can say that the RTX card is having to use more TFLOPS to do the work, so harder. The ray tracing is done mostly by the RT cores and this is what the driver update will enable, a feature that will force an equivalent of extra 23 TFLOPS, remember it is 60 FPS @ 1440p inside Metro Exodus, for a GTX 1080TI which can do 10 TFLOPS. The math doesn't lie in this case, it would be unplayable at that resolution with RTX ON on a GTX 1080 TI, so you will need to play in Full HD probably, because at 1440p it is at 1/3 frame rates that you can with RTX OFF. (just an approximation, they show it is 18 FPS in the 1st slide)

    PS: even if it was possible DLSS as a compute shader workload instead a hardware feature, it won't finish in time to deliver the frame, so it would be just an added cost to the rendering in general.
    Last edited by NilsonLima; 03-20-2019, 08:11 AM.

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  • replied
    I'm actually curious as to if it means DLSS will work on Pascal cards. If so, RT isn't entirely infeasible for games that can use DLSS to upsample.

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  • replied
    Originally posted by EA_Unreal_77 View Post
    20 FPS in Battlefield V? No, thanks! :-)
    The good news is not for playing games, it is for gamedev where several people will be able to delay the purchase of a RTX card for much longer time and also decide for a better model for their use purposes. Until we can put our hands in the graphics driver from April there is no way to tell if this is not just a strategy from NVidia to convince people to purchase RTX because now you could see how it performs against pascal. Even for games, you would still be able to decide if you want just reflections, shadows or both, so the issue on performance would not be that great.

    The key argument on NVidia's keynote now is that RT cores just accelerate ray tracing and that it is possible to have it working on Pascal aswel. Previously they lead people to understand that without RT Cores ray tracing would not be possible. This point for what I was tired to say to everyone, that the only thing necessary was to have the features implemented at driver level and would work for any card. I thinks this move will make AMD do something about their own cards.

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  • replied
    20 FPS in Battlefield V? No, thanks! :-)

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  • replied
    We just need the drivers update in April and be happy about it !!

    Last edited by NilsonLima; 03-18-2019, 07:15 PM.

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  • replied
    I do not believe so but can you ray trace reflections and shadows off of emission textures?

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