Alternative to Scene Colour node for Overlay cameras?

[royal minnow]

As title. Scene colour node produces the render texture of the base camera (and/or just doesn't work for overlay cameras). This is a problem for distortion effects as can be seen, as my setup for a 3D skybox involves the 'main' camera being an overlay on top of the 3D skybox camera, which is the base.

One lead I have is accessing another render texture in the pipeline (like the _AfterPostProcessTexture I saw one post talking about) but I'm not sure how to do that in Shadergraph. I could also, in theory, get a render texture from the overlay camera and use that in the shader... but you can't set an output in overlay cameras, only base ones.

[maiden orchid]

Why another camera?
And/or what does the 3d skybox need to do?

[royal minnow]

Because using the camera stack to composite the main camera (overlay) onto the 3d skybox cam (base) is a very simple way to set it up.

The 3D skybox is gameobjects that are on the 3DSkybox layer and are only visible to the 3Dskybox cam, and invisible to the main camera. It gives the impression of large structures/geometry in the distance without requiring a massive lightmap or having to deal with camera culling issues.

what it looks like (rough example) in game view, and what the geometry actually looks like in scene view (3d skybox cam copies the position/rotation of the main camera and sits in the middle of the greyboxes).

I'm aware of the performance overhead to having multiple cameras but seeing how simple this is to get working I feel as though it's worth it, but I'm open to other solutions if they'll get around the Scene Colour issue. (no access to Scene Colour/Scene Depth is the only real drawback)