UE5.7 Regression: UMG Background Blur with Corner Radius becomes invisible in packaged builds (UE5.6 OK)

[bengmusic]

Engine Version(s): UE 5.6.x (works), UE 5.7.x (broken)
Platform: Windows (packaged build)
Repro Rate: 100% (for me)

Summary

In UE 5.7, the UMG Background Blur widget renders correctly in PIE/editor, but in packaged builds it becomes fully transparent / invisible when Corner Radius > 0. This appears to be a regression compared to UE 5.6, where the same setup works in packaged builds.

Steps to Reproduce (clean project)

1. Create a new Blank project (Blueprint), no starter content.

2. Create a Widget Blueprint, e.g. WBP_TestBlur.

3. In the widget: Canvas Panel → SizeBox (set a fixed size, e.g. 600x400).

4. Add a Background Blur widget inside the SizeBox.

5. Set:

   • Blur Strength = 20

   • Corner Radius = 20 (any non-zero value repros)

6. In Level Blueprint (BeginPlay): Create Widget → Add to Viewport.

7. PIE/editor: blur shows correctly with rounded corners.

8. Package for Windows (Development or Shipping) and run the packaged executable.

Actual Result

• UE 5.7 packaged: Background Blur is not rendered (transparent/invisible) when Corner Radius > 0.

• If Corner Radius = 0, Background Blur renders again (but without rounded corners).

Expected Result

Background Blur should render in packaged builds with Corner Radius enabled, consistent with PIE/editor and UE 5.6 packaged behavior.

Notes / Regression

• UE 5.6 packaged: works correctly with Corner Radius enabled.

• UE 5.7 packaged: broken as described above.

• Workaround: set Corner Radius to 0 (loses rounded corners).

[BRGEzedeRocco]

Hello @bengmusic ,
It seems that in UE 5.7 this issue is related to a change in the implementation of the blur system. In one thread, a very similar error is mentioned to the one you’re experiencing, although in that case the main problem was a crash.

Background Blur Crash with 5.7 and Instanced Stereo

Hi, This is a 100% reproducible crash with the following steps in Unreal 5.7.1: Create a new project (even an empty template) Enable Instanced Stereo Create a User Widget Add a Background Blur Set the Blur intensity greater than zero (e.g. to 10) You will get a crash Fatal error: [File:D:\build++UE5\Sync\Engine\Source\Runtime\RHI\Private\PipelineStateCache.cpp] [Line: 584] Shader compilation failures are Fatal. Since we are developing a game that can run both with and without VR, we would…

They suggest trying a console command as a possible workaround(although it’s still a workaround), which in some cases could helps restore the blur’s correct behavior. This way, you might not need to set Corner Radius = 0 and lose the rounded corners.

Additionally, it’s mentioned that an official ticket has already been opened with Epic and that the team is aware of the issue, so it will likely be fixed in a future engine update.

Hope it helps!

[bengmusic]

Thank you for your reply. I’ve resolved it according to your suggestion.

[z3u5]

Hey @bengmusic, did your background blur widgets works with corner radius? I tried the command but it’s still invisible. Can you tell me exactly how did you do it? Thank you

[bengmusic]

DefaultEngine.ini

[ConsoleVariables]
UI.SlatePostBlurUseDualKawaseFilter=0