Decal Actor for (mobile) forward rendering ?

Is there anything like this Decal Actor User Guide | Unreal Engine Documentation for mobile forward rendering ? (without support for light interaction)


On mobile you can read scene depth when using translucency. So you could render mesh decal(scaled and oriented cube) without depth testing and project decal to scene. Problem is that you can’t use scene normal and you have to deal with translucent lit shading.

Isn’t there a way to avoid lit shading completely on decals? Older games didn’t have decals that interact with lighting at all.

You can select unlit if you want. It depends on use case how well how it works. What you are actually trying to do with decals?

I would like to use them to detail my level. Stains, damage, etc.

I am bit clueless what you actual try to do. Is your scene unlit? Why you need them not to interact with light?

My scene is lit with static lighting (lightmaps only). Even if I have one stationary light, having decals interacting with light in forward rendering will cause massive performance drop (especially on mobile).

In older engines decals would be affected by lightimaps of course, but wouldn’t interact with dynamic lighting at all. I would simply have to see where I am using decals and make sure I didn’t use bright decals in the dark areas of the level.

Unlit decal actors supported on mobile since 4.9. But only if MobileHDR is enabled. Not sure if they are a good option for level decoration. They are more used for effects like casting a spell.

In 4.13 there is new ray cast functionality where you can get uv’s from hit position. My dynamic foliage system use this system by reusing underlying static mesh lighmaps. System is bit complicated but it’s quite similar than landscape grass system use. I think similar approach would be suitable for small decals too. But to make this kind system more usable it would need to be exposed on editor level.

Well, Doom 3, DOOM 2016, newer Wolfenstein series and Crysis series all use decals extensively to add grime and splatter and damage to the levels. Those are static decals. They of course use dynamic decals too for projectiles damage and blood/gibs splatter.

I haven’t gotten to weapons/projectiles yet, so I don’t know how UE4 handles that. However it looks like DecalActor is a “static” type of decal which can be used to detail levels (please correct me if I am wrong).

I can’t really use HDR on mobile as it will bog down performance in mobile VR (HDR is supported, just don’t think it should be used for performance reasons).