When DOF or SSS are enabled, transparent window displays all pixels additively.

[droqen]

Tested versions

4.3-dev3 (preview build), 4.2-stable, 4.0-stable

System information

Godot v4.2.stable - Windows 10.0.22621 - Vulkan (Forward+) - dedicated NVIDIA GeForce RTX 3070 Laptop GPU (NVIDIA; 31.0.15.5123) - 11th Gen Intel(R) Core(TM) i7-11800H @ 2.30GHz (16 Threads)

Issue description

A transparent window with a 3D object rendering successfully:

Same project with DOF (or SSS on any mesh) enabled; all contents of the window appear additively blended with whatever is behind the window:

Same issue as #83939, but different method of reproduction

Steps to reproduce

1. Create a new Forward+ project
2. Enable display/window/size/transparent
3. Set up a scene with a Camera3D looking at a MeshInstance3D with a mesh, and add a DirectionalLight3D that lights the mesh*
4. Either:

• Add a New CameraAttributesPractical to the Camera3D, and set DOF Blur / Near Enabled to true, or
• Add a New StandardMaterial3D to the MeshInstance3D and set Subsurface Scattering / Enabled to true

*If there is no light source, the object disappears; I expect this is only because it is a solid black object being additively blended, which means it is blended away. Technically this is still a reproduction of the issue, but it is not as visually clear as if you add a light source.

Minimal reproduction project (MRP)

19-ForwardAdditiveTransparencyBugMinimal.zip

[droqen]

As mentioned in my comment on the other related issue, it might be worth noting that DOF and SSS are both Forward+ features.