[UE-67936] Strange material bug

Development Rendering
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1

Hi guys,
I am having this strange issue with a material function I created in UE 4.21.1. The node result work perfectly fine in 4.18. I have attached images of both versions below.
Can anyone please let me know what maybe wrong? Or am I staring at a bug :open_mouth:

Steps to Reproduce -
Open the editor, Create a material like the attached image, Select the cube preview mesh

Results:
Artifacts appear across the mesh in 4.21.1

Expected:
Artifacts would not appear (4.18 image)

263860-pixelnws-418.jpg
263860-pixelnws-418.jpg1545×777 150 KB

263861-pixelnws-4211.jpg
263861-pixelnws-4211.jpg1552×767 155 KB

2

Hello,

We’ve recently made a switch to a new bug reporting method using a more structured form. Please visit the link below for more details and report the issue using the new Bug Submission Form. Feel free to continue to use this thread for community discussion around the issue.

https://epicsupport.force.com/unrealengine/s/

Thanks

3

Thanks Jeff, just received an email from Epic regarding my bug submission. Eagerly waiting for a fix.

4

Hello, I managed to get this resolved.

If anyone’s wondering how, I clamped the Alpha’s of the two Lerp nodes (which wasn’t required in v4.18, v4.19).

268643-clamp.jpg
268643-clamp.jpg1041×695 82.7 KB

However, I just noticed that the bug report for the above issue was marked ‘By Design’ yesterday (14th Feb 19) on Unreal Engine Issues and Bug Tracker (UE-67936) .

Can someone please explain what changed from v4.20?

5

I can confirm this solved the issue for me!
Rather strange that the alpha needs to be clamped now, I know my way around the material editor and I don’t think I would solve this in a milion years, so random.
Regardnless, thanks!