Unreal Engine 4.27 Preview

Hi Epic, I’m testing the GPU lightmass and mGPU feature. I have 2 x 2080Ti GPUs running with NV link and I’m not seeing any utilization of the 2nd card when GPU light mass building.

Can you please post documentation on how to activate the feature.


Kudos to the team that worked on this release. Is there an ETA on documentation?

Hi DoubleElephantDE, I can provide that info for you. It is still a beta feature and has not yet been given a simple preference. For now there are two necessary steps:

  1. In DefaultEngine.ini under “[/Script/Engine.RendererSettings]”, add the following line:
  2. Open the editor from the cmd shell and add the command line argument -MaxGPUCount=2 . Or create a shortcut for UE4Editor.exe and add that to the end of the “Target”. You can open the editor without a project, and the argument will persist after you have selected the project.

If it’s working, the output log should have this line:
LogD3D12RHI: Enabling multi-GPU with 2 nodes

Some aspects of the bake do not yet take advantage of both GPUs, like VLM generation. If you have a heavy VLM then the relative performance gain will be lower.

Hi UElaci, this setting shouldn’t affect the path tracing render itself, which only uses real refraction. However dof for the path tracer is currently handled with the regular post-processing pipeline, and it appears this setting might be necessary to generate the correct data in the rasterized passes for the post-process to work.

It’s also worth noting that in 4.27, all refraction iors are now specified with the “Refraction” material input, including ray tracing and path tracing. The ior is no longer derived from the Specular input.

I did not read any pixel streaming production ready like you said in the video. Am I missing something?

Hi, thanks for the explanation.

So the question is now, will there be some improvement on the postprocessing pipeline to better handle depth of field on translucent materials in general?

Or is it something we can hope to get fixed at least for pathtracer?

I think unreal’s pathtracer is very attractive for archvis and maybe even product renderings however this issue can break rendering.

And this applies not only 4.27 but can be an issue for UE5 too and might force users to avoid using depth of field when glass objects are on screen.

I understand that this might be a non-issue or maybe a low priority for game development and one can argue that we can just setup scenes to avoid this problematic situation. But the more unreal advances the more these relatively small issues stand out.

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Does oodle work or am i doing something wrong. I packaged a project with some stuff in 4.25 and 4.27 and it only had a 200mb difference, funny was however when i moved it to an empty project (each) and then packaged. Oodle package was around 333mb and ue 4.25 was 221mb lol. Any information about how oodle works? Currently its worse

If you look in the comments to that video, I think you’ll find me already pointing out that it’s not actually SequenceCameraShake he’s using. :wink:

If you can find an actual video using it, please let me know!

Hi All,

I’m working through several issues in the revamped Pixel Streaming code, I’ve submitted formal bug reports but I can’t see a way to provide updates to them, I don’t want to keep submitting new ones, I have case numbers but I think they are just auto generated.

what’s the best way to engage with the team to work through the issues, happy to help test / debug further etc.



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I am long waiting for using the dynamic foveated rendering feature under UE 4.27 but did not find any documentation for that. How to use that feature on a desktop and eye tracker?

The Snapshots feature is a good first step, but it only seems to work to save Actor locations and transformations, not material or blueprint properties.
This really limits its usefulness IMHO.

Remote Control Web Interface error in editor with UE4.27 preview 1

i Install the 4.27 preview 1 from the Epic launcher.
after enable the plugin, i got this message in editor :

“Failed to launch the Remote Control Web Interface
Missing files in WebInterface folder”

there is only the tps folder inside the WebApp.
if i compare to UE 4.26.2 with the marketplace plugin : RemoteControlWebInterface , the webApp folrder contains others folders like Client , Server …

Any ideas ?


NDisplay launcher and the new workflow

How do you launch a project in Editor -game mode with the new Ndisplay workflow in 4.27 preview 1 ?

the Ndisplay Launcher needs a config Files … how do you add the Ndisplay Uasset ?


Remote Control OSC with 4.27 preview 1

Relative location is a Vector 3 (X,Y,Z)
how do you control only the X value with a OSC remote slider with TouchOSC or other OSC remote Apps ?

my slider control all the vector values (XYZ).


Switchboard seems to be the replacement for the launcher

Did you try the DOF hack that’s been used til now? It’s a bit messy, but better than no solution. Here’s a quick explanation: Duplicate the Mesh and disable “Visible in Raytracing” on it. Apply an opaque white material to it with a Pixel Depth Offset 1 in the material attribute. I usually also parent the duplicated mesh to the original so it moves with it.

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Web remote control in editor works fine with UE 4.27 github source.

Exactly what i’m looking for !

Thanks, the trick works for pathtracer.

Web Remote Control with NDISPLAY : No preset available

I got NO PRESET AVALAIBLE in my browser window when i try to reach the WebRemote control app with myIP:7000 In NDISPLAY mode.

it works great within the Editor with of course the same Virtual Production default template.

in editor, i drag the remote preset in the world container.
I launch Ndisplay device via Switchboard.

a solution ? please ?