Thanks for checking in. In the image below I want the globe to be casting a shadow on the background, which as far as I can tell is only possible if the background layer has 3D toggled on so that I can use material options to accept shadows (i've double checked all the material options for the layers). However since I also have a camera active, turning 3d on locates my background in space, whereas I want the background to remain at a constant size independent of camera movement, i.e I want everything but my background to be affected by camera movement. I'm aiming for a background which remains the same throughout the sequence with a shadow falling on it from the globe. I really hope that all made sense and any tips would be very much appreciated!
P.s pic attached below, note that when 3d is on the background layer is now affected by the camera moving forward. I guess it is possible to compensate by scaling the background image with the camera movement but this is clumsy since it has to match exactly.
You can apply an expression to the scale of the 3D background layer that uses the distance between the camera and the layer to keep it the same apparent size. It is one of my animation presets. Here it is: Dropbox - 3dlayerscaletocamera.ffx
This is the expression:
C = thisComp.activeCamera;
CP = fromWorld(C.toWorld([0,0,0]));
L = thisLayer
LP = fromWorld(L.toWorld(anchorPoint));
d = length(CP, LP);
z = C.zoom;
r = d/z
r * value