Thank you! This is done with Viewports and shader materials (mapping a ViewportTexture across SCREEN_UV). Do you have a link to any information about the new portals? I’ve ran into some issues with my approach due to difficulties with implementing efficient culling or timely updating viewports.
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Nice solution! Really liked it. If you want to check the new portal implementation, it is already merged into 3.4 branch, and the details can be checked in this PR.