Godot version

4.0.beta7

System information

Fedora 36, Vulkan Forward Plus, AMD Radeon RX 6900 XT

Issue description

When enabling temporal antialiasing, the viewport becomes opaque if it's currently transparent.

This does not occur with FXAA and MSAA, both of which support transparent viewports (with some visible artifacts though).

TAA disabled	TAA enabled

If it's not possible to support TAA on transparent viewports, I suggest making the transparent viewport property take priority (so it disables TAA), and print a warning if both TAA and transparent viewport are enabled.

Steps to reproduce

• Enable Display > Window > Size > Transparent, Display > Window > Per Pixel Transparency > Allowed and Rendering > Transparent Background in the advanced Project Settings.
• Notice how the editor 3D viewport (and the running project) features transparency.
• Enable Use TAA in the Project Settings.
• Notice how the editor 3D viewport (and the running project) loses transparency.

Minimal reproduction project

test_taa_transparent_viewport.zip