Vulkan: transparent_bg property in SubViewport has no effect (not reimplemented yet)

[flomar]

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Note: This issue has been confirmed several times already. No need to confirm it further.

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Godot version: v4.0.dev.custom_build.3811fb919

OS/device including version: Arch Linux, GeForce GTX 1070Q, Vulkan

Issue description: Enabling the "transparent_bg" property in SubViewport seems to have no effect. The 3D content within the viewport is rendered fine, but the underlying 2D content (ColorRect, TextureRect, etc.) is hidden below a black background. The expected outcome is to have the 3D content rendered on top of the 2D content.

Note: I'm aware 4.0 is anything but stable, so I'm wondering if this really is a bug or some problem with my machine. If anybody could test this, maybe on Windows, I'd highly appreciate it.

Steps to reproduce:

- Node
-- CanvasLayer
--- ColorRect
--- SubViewportContainer
---- SubViewport
----- Node3D
------ Camera3D
------ DirectionalLight
------ MeshInstance [Sphere]

[fire]

See godotengine/godot-proposals#888

[lupoDharkael]

The material preview appears with a black background as described here, still reproducible as of 706c38a

[MrJoshBowman]

I'm getting the same issue on MacOS and Godot v4.0, transparent background option does nothing but set the background to black.

[BenjaminNavarro]

I confirm the bug is still there 92a2380, would be nice if someone could take a look at it

[kalysti]

Same bug in windows. Just to notice. Transparent BG Option -> Black Background.

[KoBeWi]

The option does actually work (at least as of 8485d0c), but only if you use 2D. As soon as there is 3D node on scene (or in viewport?), the background is no longer transparent.

[joeyeroq]

Godot 4.0 alpha 1 and still not resolved, transparent background is a much needed feature.

[CrezyDud]

if there's an environment, the sky is also still rendered (instead of black).

also needs to be done

[SaveToTheADrive]

Until this is fixed, as a really janky workaround, you can assign a CanvasItemMaterial to the SubViewportContainer, and set its blend mode to "Add". Whatever you're rendering to this viewport will probably look a bit transparent, but it allows you to keep working while using the viewport and also being able to see everything else.

[CrezyDud]

Until this is fixed, as a really janky workaround, you can assign a CanvasItemMaterial to the SubViewportContainer, and set its blend mode to "Add". Whatever you're rendering to this viewport will probably look a bit transparent, but it allows you to keep working while using the viewport and also being able to see everything else.

thanks

[joeyeroq]

Not a workaround at all. As CrezyDud said, the environment needs to be factored in as well as in part of the alpha when "Transparent Bg" is checked on.

Godot 3 displays correctly.

[djmaesen]

post processing works in my project with a subviewport and a second camera for first person weapon rendering
transparent background doesnt work however

[golddotasksquestions]

transparent_bg kinda works for me (Win, dedicated Nvidea 765M), but SubViewport is also completely broken, so it's really of no use:

subviewport01.mp4

[djmaesen]

just checked it in godot alpha 3
transparent background still doesnt work, post processing does
please fix this in alpha 4

[Calinou]

just checked it in godot alpha 3 transparent background still doesnt work, post processing does please fix this in alpha 4

Contributors work on a best-effort basis. As per Godot's MIT license, there is no warranty provided for anything 🙂

[joeyeroq]

I did a quick test of Chaosus's pr, looks good. Hopefully it will pass all reviews and checks and will be in master and this issue will finally be resolved.

.