HDRP - Decals render on both sides of object.

I see decals seem to have a normal or an arrow pointing in the direction of the projection, however, it renders the decal on both sides of an object. And the backside render (the one that shouldn't be there), actually doesn't render correctly.

Good:


NOT Good:




Anyone have a solution to this? Is it a bug? Is it by design?

 

Did you find a solution for this? Because I have the same issue, and I cannot find an answer.

 

I haven't tested decal behavior seen on this thread myself, but there are two things you can try to fix that:

- if you don't need any decals on the backside, then on the backside material just toggle off "receives decals" (or whatever the material option for that there) on the backside material.
- if you use new enough HDRP to support Decal layers, it comes with angle option that lets you limit the angle/surface normal where the decals can project. Afaik it could be used to prevent scenarios like in this thread too.

 

My issue was simple to undertand but harder to fix. I setup an objet in blender to have the rear side of a door share the same UV coordinates as the front side of the door. Mainly because it was a texture atlas and I needed room in the 2k texture for other textures...........

I cant really get around it, without alterting my UV arrangement. Other objects like primitive Cube work fine with no issue.

Essentually is was my artwork

 

set inspector option to debug and it gives option, Start Angle Fade and End Angle Fade

edit3:
I just realised the slider for Angle Fade is a MinMaxSlider with both are set to max value and I was selecting the slider to move I was selecting the End Fade slider, which moved the Start Fade one, I didn't know sliders could range an upper and lower value

edit:
Forgot to say this is URP
It seems to have fixed the decal being drawn through an object, even after switching back to normal inspector!! I've not tested quit, reloading etc to see if it's stable.
edit#2
Seems to still be correct when loading project .

 

If you just want to remove the annoying glow on the back side of the decal you can uncheck the Normal in the Materials Surface options. This worked fine for me because I dont use that much normals on my decals and that was the most annoying part for me