Raytracing is not active , is it because i dont have RTX ?

My Pc graphic card is 980 and unreal engine raytrace is not active as u can see in the attached image to be enabled , is that means that this feature is only available for RTX card exclusively , what about those who cant afford to buy the RTX cards , and is that mean also that 1080 ti will not support it also with its 11 GB ram ,

You need an RTX card.

This have been explained quite sometimes already, it won’t work for every card and it is not Epic’s fault.

Epic’s responsibility: develop an engine vendor agnostic with features that can be used in several OS. This is achieved when the developer uses API standards and regarding this Epic uses: OpenGL, Vulkan and DirectX.

Graphics card vendor: develop top edge hardware, which can run in most hardware and OS. For the same card to work in several OS with several applications, the card vendor needs to implement the low level API mapped to standards: OpenGL, Vulkan and DirectX with their device drivers.

DXR is a feature from DirectX and stands for real time Ray Tracing, so it is an extension module with specific API inside DirectX.

For Unreal to work with real time Ray tracing, the devs still needs to follow standards, so they will map the rendering module to work with DirectX+DXR and Vulkan+Raytracing. Currently the only card with drivers with support for Vulkan+Raytracing and DirectX+DXR APIs with mapped functions for real time ray tracing are the NVidia’s RTX cards.

So, if AMD (or even Intel with their future graphics cards) publish new drivers with the necessary mapping Vulkan+Raytracing and DirectX+DXR, their cards will work out-of-the-box with the engine. The same for previous card generations from NVidia, meaning it will only work if they implement the features explained above into the drivers for the previous card generations.

Know that GTX 1080TI is capable of approx 2.2 GigaRays maximum, so you won’t see anything real time while using this card if NVidia decides to implement the drivers. The lowest end RTX card is capable of 6 GigaRays maximum and it is already really limited on performance.

I understand that people who do archiviz would benefit having previous NVidia generations working on this, but the public is short compared with gamers (main NVidia focus right now) and also since NVidia’s sales are short according to latest reports, it is unlikely they will release drivers with DXR enabled with the risk of not selling the new cards… sad, but true.

This is actually the main core of the problem and it really hearts to watch nvidia deliberately igonre the dxr driver support for the 10 series to achieve more money from selling their RTX card , am not blaming Epic for this but at least they should support their users with the minimum effort even by informing their users about this so at least everybody will know what nvidia is doing , the prices of the 10 series are dropping down because of this and it will increase the 20s series just like the miners did , and at the end only those who can afford to buy an additional RTX card or sell their 10 series for less then their original price just to catch up with this.

i understand that RTX is much more faster in raytracing but atleast help us develop it and test with our slower 10 or olders series

I would still recommend the GPU solution for rendering atm, and wait more for the engine final release 4.22 and maybe even 4.23, before going into purchasing a RTX card. If it is to purchase, at least purchase something which worth per use case.

Currently my stand for a purchase (new card or upgrade of Maxwell):

gamer: RTX 2070(min) RTX 2080 (recommended)
gamedev: RTX 2060 (min) RTX 2070 (recommended)
film: RTX 2080 (min) 2 x RTX 2080 (recommended)
archiviz: RTX 2080TI (min) 2 x RTX 2080 (recommended)
professional film: RTX 6000(min) RTX 8000 (recommended)

The cards are just too expensive and buying one below what you need will just make the things worst. I will wait more before going into purchase myself, for now the table above is my feeling, it might change. I just have several use cases at work, so I need to upgrade 5 machines, I have to do it right.

Didn’t Microsoft also remove the DXR fallback to allow any DX12 GPU to support ray tracing, but at a performance hit?

The fallback was removed, it was only necessary when there was no DXR capable card and also to help developers with the new API, the only way to have everything working for old generation GPUs is for each vendor explicitly implement the feature in the drivers and this is why Microsoft left the fallback code public available. As I didn’t study the code, it is uncertain if the code is only fit for DirectX (most likely) or can be used for Vulkan somehow (very unlikely).

Just a note that UE4 does not support NVLink for multiple RTX cards, so you can only use a single card right now.

For now that is correct. They have been asked several times and didn’t answer, so I am guessing they can’t answer for now, but they did make multi-gpu card rendering for the Star Wars demo at last year’s GDC. I have posted up there 2 x cards because they work on other 3D applications used at those workflows.

I really wish UE supports multi-gpu because cost wise 2 x RTX 2080 besides being the same price as 1 RTX 2080TI, ends with more memory thanks to NVLink when compared with RTX 2080TI, otherwise you would need RTX Titan which costs 4 x RTX 2080… so it is a NO.

Yes, it’s something Epic would have to add support for so it depends if it’s worth it to them, it’d be mostly useful for developers.

The fallback is a library that mimics the DXR APIs as closely as possible and implements ray tracing using DX12 compute shader behind the scenes. However, according to its readme file, it’s not a drop-in replacement because true driver level DXR support requires a couple features that are not in DX12 compute, like arbitrary GPU memory pointers, and require applications to implement the workarounds themselves. It’s also not guaranteed to behave the same as native DXR support.

The fallback was never part of DirectX or any drivers, so it was never “removed” because it was never there. The OP’s recurring complains about RT not working on his 980 are no different than people complaining about shaders only working on cards that supported it back when they were first introduced.

It’s absolutely not worth Epic’s, Microsoft’s or NVidia’s time to support a software emulation layer that is going to run at non-interactive frame rates for a feature which entire’s purpose is to enable ray tracing in real time, just so devs can see pretty RT slideshows a couple years before they can afford hardware which supports it.

I guess everyone know by now, but this month Nvidia is to release driver enabling RTX support on 10 series cards at least. It will still not perform very well - but at least it will be enabled in the new upcoming drivers.

With the Nvidia drivers out, can any one confirm if they were able to make it work on a 10 series card?
I am trying on my 1080 TI, enabled the features from project settings, on each light and the post process volume but I am not able to see it working.

im making progress.

  1. You have to have the latest version of Windows.

  2. You need the latest game ready drivers from Nvidia

  3. You need to launch UE4 with -dx12. — Create a shortcut executable for the engine. Right click it, go inside of it, after the .exe" add -dx12.

  4. Launch UE4. Now you will be able to select raytracing in project settings, and it defaults to activate skin shading something or other, requires a restart.

  5. Try some reflective materials. Set lights to movable… and you should be able to control the settings with a post process volume…

im getting some weird artifacting, but its ‘working’… Others are clearly having better results. But im trying to wrangle this amidst taking care of a toddler.


thats my result so far. People in the other thread are claiming its working, but at low FPS. So might wanna check out that thread… someonen posted a link to Nvidia’s blog instructions.

Good luck, keep me posted. im on 1080ti as well.

Checkout post #33,

I am able to see the realtime raytraced reflections while working in the editor - BUT - when I package the project - and play it - the reflections are not raytraced anymore. The reflections are the old screen space reflections. Am I missing something?

Do you have DirectX 12 turned on for the built project?

-forgot this:
Under Platforms > Windows, use the **Default RHI **dropdown to select DX12.

…working now!!!

Thanks Darthviper107