Hi,
It seems that DecalMask Mode was removed from Buffer Visualization Mode list. This is intentional or it’s a bug?
Hi Matuesz,
Thank you for reporting this. I have submitted ticket UE-27569 for this to be investigated.
-Tim
Actually, this was removed since it’s no longer part of the GBuffer and is not easily available for later passes. This may be added back in the future with a ShowFlag option, but there are no current plans to implement this with 4.11.
Thank you for the quick response. So it’s not a bug, it’s a feature 
Yeah, not a bug. Unfortunately, I didn’t find anything directly mentioning its removal. After discussing with a dev this was a deliberate change. The showflag should eventually make it in though, but not sure when they’ll implement it.
Hi, Tim
Is the ShowFlag option still not available for 4.12.5?
We are trying to output some images with alpha, using the decal mask as a substitution.
Please, let me know if there a way to get support to make the decal mask work.
Thanks,
-Alex
It hasn’t been added back that I can see.
I see. Thanks for the quick response!
Ryan’s ImposterBaking tool used this viewmode for generating alpha masks, so this effectively stops it from outputting them.