Decal on unlit issue & DBuffer broken in 4.8

Hey guys, I’m projecting a decal material into my scene and it doesn’t appear at all on unlit materials. This is a huge problem since the scene uses baked lighting so I only see my decal on the scene capture icons. According to this question already asked, the problem was resolved in 4.7.6 but it appears to have returned in 4.8.

For good measure, I tested this in a fresh install of 4.8 as well and followed the steps outlined by Scottsmi in the last answer of this question. What happens then is when I switch the decal to render with a DBuffer setting, the decal doesn’t render at all.

I need a fix for this urgently so the sooner someone can help me confirm if this is an engine issue or some weird driver bug on my machine, the better. Thanks!


Sorry, but decals not work with unlit material.

Thanks for the quick reply!

Really? Even if I use the decal buffer? I thought the point of that was to be able to use decals without relying on lighting to project decals. So I assume it was never actually supported then?

Is this ever going to be addressed? Decals are pretty great and I would love to be able to use them to enhance scenes with baked lighting.

edit: I decided to test decals on unlit materials in 4.7.6 and yes, it does work in the previous version as you can see:

As far as I can tell this is either a bug or there was a reason that this was removed, and if the latter then I would like to know why.

Is this a bug? Or intended functionality? I’m having this issue myself in 4.8.1. My game is entirely unlit for mobile performance reasons and it’s a shame I can’t use decals at all apparently. :frowning:

Hello Phillip,

I recreated the issue you are experiencing. This is a bug and it has been reported to the development team. The ticket number is UE - 18405. Thank you for reporting this issue.

And thank you for looking into it!

I’ve read conflicting information about decals on unlit materials. Is this bug still outstanding?

In 4.11 I cannot project translucent or stain decal textures onto unlit materials. Emissive decals work (which makes sense, since they are additive).

We’re working on a mobile title that uses 100% unlit materials. Is there currently any way to project modulated/stain or translucent decals onto unlit materials?

I would think this would be basic functionality even for games that use lighting since, for instance, blood could splash onto a light fixture that uses an unlit material. Surely you’d want to be able to project a translucent decal onto the light material?

Just an update on that. Emmissive decals don’t appear to work either on mobile devices. I assume this is because mobile uses a forward render, while decals are deferred? We have also disabled the gbuffer on mobile, so I suspect that may have disabled decals as well, since they are rendered during the lighting pass as far as I understand. It would be great to have decals work on mobile, and for translucent and modulated decals to work on unlit materials.