I'm using a "Screen Space - Overlay" canvas for my game (the whole game is menus and tiles and such like a board game, so the entire game is inside the canvas) with Reference Resolution set to 1920x1080, which keeps the canvas object in 3D space set to that size and adjusts the scaling factor. This works correctly: Narrower aspect ratios give me black bars above/below just like I want. However, I want to render 3D things like objects and particle systems *behind* the UI elements and have them lined up properly. However, since it doesn't work to have the 3D objects actually in the Canvas (pretty sure 3D objects can't be given a RectTransform), I can't figure out a way to get things to line up. The game automatically changes the camera's viewport ratio to match the screen's ratio which is how all of this works, so I can't just create a GameObject with the same dimensions and scaling of the Canvas, and if I switch to a world-space canvas, that'll break all the nice auto-ratio-handling. What's the real way to do this?