I want to achieve fairly accurate 3d layer stacking of bitmap images.. Sort of like the images I've attached (appears below), but with accurate perspective. I'm doing this with screen-shots (for press), so any insights to how I should be treating them prior to import would also be very helpful (resampling etc). This would be easy as pie with Freehands perspective gird… but trying to get this to work with illustrators 3D rotate is driving me nuts.
Good question Jim. This is actually a great question because it forces you to think about how Illustrator's 3D feature works. I haven't taken the time to try to match the exact same angle that you showed in your example, but maybe this technique will help you visualize it yourself. Likewise, I hope it will help others learn to take advantage of the 3D Extrude feature as well.
Ok, so first, we need to define symbols. These symbols will be the screen shots that you mention (so when you place them into Illustrator, they will have to be embedded, not linked). Once they are defined as symbols, you'll be able to map them to the surface of a 3D object.
Next, you need to create the geometry for the 3D objects themselves. The first thing is that you're dealing with multiple objects here, and Illustrator's 3D feature treats every 3D effect as if it were in its own 3D world -- meaning each object has its own vanishing point. If you want multiple objects to share the same vanishing point, you have to group them first. But that's not the biggest of problems here. Because you have multiple shapes that are spaced apart, and that are each extruded, all sharing the same vanishing point. You can't specify a distance between objects when they are stacked one on top of the other.
The solution is to head to the "top" of your object and "look down" -- build the geometry of your 3D objects as though you were looking at them from above. Using a top-down approach, you can build spacing of the objects. And rather than extrude to add depth to your objects, you'll be adding the extrude to add width to your objects. Below, you see the geometry that I created, as if I were standing above the shapes and looking down. Not only have I spaced out the objects, I've also offset them a bit, to allow each one to jut out just a bit, to better achieve the effect I think you are going for. Once this is done, you would group all of these shapes together so that they can all share the same vanishing point.
Now, apply the 3D extrude effect to the group. The extrude depth will add width to the shapes, and you'll adjust the rotation and the perspective to match the look you're going for. Then, map artwork to the "fronts" of all of the shapes. Be sure to also check the Shade Artwork button to achieve a better lighting effect. Adjusting the lighting will also give you better results.