Decal Nodes for COMPATIBILITY RENDERER

[Axis4s]

Describe the project you are working on

A Simple 2.5D RPG Game

Describe the problem or limitation you are having in your project

I've been trying to create blob shadows but not being able to use the decal nodes is very annoying and complicates the process, i did manage to come up with a fix for my project but it is very hacky.

Describe the feature / enhancement and how it helps to overcome the problem or limitation

The Decal node that is already built into godot but it also supports the compatibility renderer.

Describe how your proposal will work, with code, pseudo-code, mock-ups, and/or diagrams

This is mostly related how the engine render graphics internally which i don't have much knowledge on.

If this enhancement will not be used often, can it be worked around with a few lines of script?

This is more about QOL and consistency

Is there a reason why this should be core and not an add-on in the asset library?

Because its a built-in feature of the game engine, which i doubt can be replaced by addons

[antzGames]

I built a plugin that provides both instanced and non-instanced decal node functionality for the Compatibility Renderer in Godot 4.4+, packaged as an easy-to-use plugin.

I think it would be a good start on what is needed. Given the fact that I got 20% with poor shader skills, I am sure someone who knows what they are doing could bang this out quickly on C++.

GitHub repo: https://github.com/antzGames/Godot-Compatibility-Decal-Node

Here is a YouTube video: https://www.youtube.com/watch?v=8XnH3mT1C-c

This plugin is currently experimental and not recommended for production use.

🕵️ I'm seeking expert-level shader assistance to help resolve the current limitations listed below.

Known limitations:

• No support for normal maps, ambient occlusion, roughness, metallic, or emission textures.
• Decals are unshaded (no lighting interaction).
• The mesh is front-culled as a workaround to prevent decal clipping artifacts. (This hack addresses the issue where decals disappear when the geometry intersects with the camera.)
• No cull masking. Any geometry (like a player) that moves into the decal geometry will get the decal projected on it.
• No support for fading curves (start/end with curvature). Only basic start, end, and power levels are available.
• The nodes do not work with the Forward+ or Mobile renderers. Use Godot's built-in Decal node when targeting those renderers.

Tested on Godot 4.4.1 on Windows (NVIDIA RTX 3050) and Linux (Intel Integrated Graphics) platforms.

Features

• Projects decals onto uneven surfaces (e.g., terrain or complex geometry).
• Decals can be projected onto both floors and walls.
• Adds two new nodes to Godot 4.4+:
  • DecalCompatibility extends MeshInstance3D, which should be used when only one decal is needed.
  • DecalInstanceCompatibility extends MultiMeshInstance3D, which should be used when you need large amounts of the same decal, like bullet holes.
• No need to modify shaders—fully usable via the Godot editor Inspector.
• Full transparency support.
• Easy fading controls with start, end, and power parameters.
• Individual decal alpha control when using the DecalInstanceCompatibility node.
• Fully documented code.
• Includes two demo scenes:
  • Demo.tscn shows moving, rotating, fading, distance culling, transparency, color modulating, instancing decal examples.
  • Instanced.tscn shows 1000 instanced bullets rendering with just ONE draw call.

Other screen shots of plugin: