Decals implementation

[AndreaCatania]

I'm opening this issue to talk about decals implementation.

The decals are a really useful feature and you can see it in action here: https://www.youtube.com/watch?v=rUOKIrfpHGw, you can use it to create bullet holes, footprint, blood / dirty in the walls, etc..

If someone is looking on something new to implement, this could be an idea.
In ue4 this is how it's looks like in editor: https://youtu.be/ANCm_EMfjP4?t=45s

[CptPotato]

I didn't use godot for much 3d yet but I assumed that decals were implemented. If this is not the case I think this should be done as they're very useful for many things.

They might not integrate as seamlessly as in UE4 (since UE4 uses deferred rendering, godot doesn't) but should still work very well.

[Zireael07]

No, decals are not yet in core @CptPotato. I believe someone made a fake decal addon that basically uses quads and some shaders?

[CptPotato]

You can do it using a projection volume (easier than it sounds) after the opaque pass. In OP's UE4 video you can see this volume pretty well.

That's how it's done in most cases afaik. Static sprite-quads are good (and faster) for flat walls but other than that a projection is required for good results.

[insomniacUNDERSCORElemon]

I'm not sure how it stacks up or if there are better ways, but I have this Valve technique (high-res textures computed to low-res distance fields) bookmarked:

https://steamcdn-a.akamaihd.net/apps/valve/2007/SIGGRAPH2007_AlphaTestedMagnification.pdf

[CptPotato]

^ this is an interesting paper. Though it's more about vector-like filtering not the decals themselves. iirc, Godot supports distance field fonts which is the same technique as this article describes.

[pgruenbacher]

https://github.com/Mr-Slurpy/Screen-Space-Decals
Screen-space-decals implemented here ^

Dumping some of my blog notes.
http://blog.wolfire.com/2009/06/how-to-project-decals/
http://blog.wolfire.com/2009/05/decals-editor-part-one/
https://pompidev.net/2014/12/02/projecting-a-dynamic-decal-on-a-3d-mesh/
https://mtnphil.wordpress.com/2014/05/24/decals-deferred-rendering/
https://bartwronski.com/2015/03/12/fixing-screen-space-deferred-decals/

[pgruenbacher]

that being said the scree-space decals has a lot of issues that I haven't been able to overcome like only rendering it on specific meshes, side stretching, etc.

[anderlli0053]

Anything new on decals? When they will be added? Why so much waiting for it, as it is vital part of game creating?

[Calinou]

@anderlli0053 While they are on the roadmap, rendering features will likely only be added in Godot 4.0, as work in other areas is currently being done for Godot 3.2.

In the meantime, you can use a third-party screen-space decals implementation.

[anderlli0053]

Aha Ok, thank you for information!

[Calinou]

This was implemented in #37861, closing.