Unreal Engine 5.1 Preview

Apparently, if you disable fast math optimizations in the project settings, this goes away. However, it needs to rebuild.


Possible bug in 5.1 preview 2: everytime I “Reimport base mesh” from the Mesh viewer, a new material slot is being added. I import as Nanite mesh.

Possible bug in 5.1 preview 2: in texture editor with a 16 bits png texture grayscale used for displacement, changing the compression settings to “Displacementmap (GB/16)” makes the texture display all red. The texture is properly handled though (like for modeling tool’s displacement) but we cannot visualize it properly in the texture view.

Bug in 5.1 preview 2: using LightWeight Mesh Instancing (plugin), sometimes meshes disappear from level as they are converted to LWI (even when restarting the editor). LWI is an amazing feature, I’d love to see it fully operational in 5.1 release, it doesn’t seem there is a lot of work left to have it working.

Edit: problem is not always reproducible, I had a case where the meshes would not disappear. Not sure yet what is causing/not causing it.

Other issues I’ve found:

  • Convert 2 meshes into LWI, then select each of them and change their transform properties: sometimes the transform properties apply to the other instance instead of the one selected. When this happens, when selecting an instance, the gizmo jumps to the other instance(!).

  • END key doesn’t place instances on the ground as this is the case with regular static meshes.

yes, that same for me, I’m calling Widget->SetPositionInViewport from c++, and the Widget always stays at (0,0)


… and there is a fix for this on /Main branch, but sadly not (yet) integrated into 5.1 branch, hope they do this before releasing 5.1

This seems like an incredibly frustrating issue. I would probably skip 5.1 if this is not resolved.



I hate the SM6 very heavy and slow, compile even by clicking…

7 years using Unreal Engine, but what a disappointment and very slow to Fix , before adding more Bugs.

Created a new VR template project using 5.1 preview and it crashes right after clicking on VR preview. This doesn’t happen with 5.0

Assertion failed: DepthSwapchainDesc.Extent.X == SizeX && DepthSwapchainDesc.Extent.Y == SizeY

Does EPIC have integration tests and regression tests running when an update is made to the engine ? Every update breaks things that used to work, for no reason.

It’s called preview for a reason. But this bug seems to be already fixed on github so just wait for the next preview release. Although judging from the commit message you can probably work around it by disabling any resolution scaling/upsampling.

Compiled it on Ventura/arm64 but using Xcode 13, works fine.

Have you noticed any hitches when working in the editor when enabling DX12 sm6? I have the same card and its really annoying to work with the editor like this.

I don’t feel like it’s been all that different but I have it paired with a 5950x and the engine itself is on an NVME.

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UE 5.1 Preview 2 intermediate file is over 100GB why is this file so massive? It is taking up almost 1/3 of my hard drive space.

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Library, click version , options and disable what you don’t use, android linux etc.
you save up to 50% GB

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After getting the 5.1 branch compiled on Apple Silicon and running great (and fast!!), the only problem I am having is that Quixel Bridge (2022.1.0) is crashing the editor when I try to open it.

Any ideas anyone?

I’m not able to make the interaction between two blueprints from a variable. The player or controller variable key doesn’t seem to work for me. This is normal?

Do you already have an estimated date of when the official will be released?

I have the same issue! have u solved it?

Object ID render is not working

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Did you ever get more info regarding this?