Note that in the "larger" div (which is actually the same size, but translated towards the camera and so appears larger), the mouse position from e.clientX/Y is being calculated based on the actual position of the mouse, and isn't being corrected for perspective; on the un"zoomed" div the mouse position ranges from (0,0) to (200,200) as expected, but on the zoomed one it's from (-42,123) to (222,315). How do I get the position where the mouse is on the actual version? Do I have to reverse the perspective calculation myself? Note that I could in theory just say "OK, the position is the mouse position I'm given, scaled by the "apparent width" of the div, but I don't know what the apparent width of the div is.