Put misc. 3D tool visible instances on their own layer

[RandomShaper]

This makes that visible stuff invisible to ReflectionProbes, whose preview in the editor shouldn't involve them.

Otherwise you get this in the editor (not a big deal, but neither desirable):

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This code is generously donated by IMVU.

[akien-mga]

Can this be used to fix #8485 / #8140?

[RandomShaper]

Good question, but I don't think so.

[JFonS]

They are separate issues. Post-process effects are applied after everything is rendered to the viewport, by then any information on the render layer is already lost.

In order to keep gizmos unaffected by post-processing we would have to render the scene first, apply the effects, and then render the gizmos on top of that. But that would create other problems with transparent gizmos and effects that distort the original scene.

[akien-mga]

Thanks!