4.21 to 4.25 mesh overlap flickering and viewport

Development Rendering
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1

Hi everyone,

I have a problem after updating the engine version from 4.21 to 4.25.

I get a annoying flickering when 2 meshes overlaps.
This issue is stronger when two meshes have different material (or when a translucent material overlap a non translucent).

E.g.: if i put on the scene 2 cubes, one next to the other on the same line, and they overlap a little, that overalpping part is flickering a lot.

More, in the viewport, when I move the character, on Unreal 4.25 the character’s camera flicker.

Here 2 videos that show the difference between version 4.21 and 4.25:

https://www.youtube.com/watch?v=5wRWXYfoRzw

https://www.youtube.com/watch?v=1TENv7GL_NE

When I was using the 4.21 engine with the same project I had no problems.
Any suggestion?
Thanks

2

The same happens in 4.24.2. I had to set the meshes off from each other by 1 UE unit. I don’t know what it is caused by or hot to fix it without offsetting the meshes by a unit. Try looking up z-fighting in the AnswerHub and forums. There’s also translucency sort priority, which I’m not sure if it affects a solid mesh next to a translucent one. I thought it was in reference to one in front of the other.

3

Thanks Presto for your reply.
I discovered that it’s a problem of materials.
For example, the “TWO SIDED” materials have this problem. If you uncheck the “TWO SIDED” option the problem disappears.
But the problem appears also if you overlap 2 meshes made of different material.
Anyway, in 4.21 engine it worked perfectly.
How is it possible to communicate this issue to Unreal Engine staff?

4

One way is to submit a bug report. Another is to start a feedback thread/topic in the forum. Not sure what’s more effective / reliable.

https://forums.unrealengine.com/unreal-engine/feedback-for-epic

5

Hello,

****** HERE’S FLICKERING FIX *********************

Official 4.25 and 4.26 having some glitches in calculations, namely TemporalAAHistory structure was not filled out correctly

Here’s the only solution that will surely fix for both 4.25 and 4.26 versions (building from the source and fixing engine glitch), since 4.25 will not have any more updates and 4.26 also has the same issue:

  1. get Unreal 4.25  source, following link is a step by step instructions on how to get the source (no need for the building until  you change buggy scripts, just when you get 4.25 source unzipped from git, run Setup.bat, after that run GenerateProjectFiles.bat ): Building Unreal Engine 4 (UE4) From Source Code / GitHub - YouTube

  2. change this 2 scripts as explained in the below link, and finally, build the source 
    https://github.com/EpicGames/UnrealE...48f5a38dfb53ea

  3. compile your project from source (in the following link, instructions are around 8.50  min): Building Unreal Engine 4 (UE4) From Source Code / GitHub - YouTube

Enjoy again your UE4.25/26

Cheers,
Mike

6

Hello,

****** HERE’S FLICKERING FIX *********************

Official 4.25 and 4.26 having some glitches in calculations, namely TemporalAAHistory structure was not filled out correctly

Here’s the only solution that will surely fix for both 4.25 and 4.26 versions (building from the source and fixing engine glitch), since 4.25 will not have any more updates and 4.26 also has the same issue:

  1. get Unreal 4.25  source, following link is a step by step instructions on how to get the source (no need for the building until  you change buggy scripts, just when you get 4.25 source unzipped from git, run Setup.bat, after that run GenerateProjectFiles.bat ): Building Unreal Engine 4 (UE4) From Source Code / GitHub - YouTube

  2. change this 2 scripts as explained in the below link, and finally, build the source 
    https://github.com/EpicGames/UnrealE...48f5a38dfb53ea

  3. compile your project from source (in the following link, instructions are around 8.50  min): Building Unreal Engine 4 (UE4) From Source Code / GitHub - YouTube

Enjoy again your UE4.25/26

Cheers,
Mike