This question about the 3D Extrude effect came in from Dyske Suematsu:
This is really puzzling me. I can't find an easy way to extrude type without shifting the perspective of the type itself. It is a very common effect. It's basically the same as dropshadow but instead of soft-shadow, it's block-shadow. But, not just copying the type and shifting it several pixels down and right. I need a real extruded look; so the front part must be connected with the back part. Do you know how to do this easily?
Unfortunately, there's no easy way to do this in Illustrator. In fact, I can't think of a difficult way to do it either. Here's what the problem is. Illustrator's 3D effect is a bit different than what you might find in other apps -- either CorelDRAW or FreeHand, or Maya or Strata. In CD or FH, the Extrude effect is created by controlling the extrusion. The object pretty much sits there, and you extend and adjust the extrusion of the obejct -- kind of like the drop shadow effect in Illustrator, as you had pointed out. In programs like Maya, you have the ability to control the object in a 3D world, but you also have the ability to position the camera to view that object from any angle.
In Illustrator however, the camera is always stationery. You cannot adjust the camera at all. The settings in the 3D dialog allow you to rotate the object in front of the camera so that you can view the object in different ways. Here's how I think of what you can do with 3D in Illustrator. Pick up an object and hold it in your hand -- stretch out your hand in front of you so you're looking right at the object. Now, you can use your fingers to see different views of the object, but you can't move your head or your arm from side to side or even top to bottom. If you move the object closer to you (by bring your hand closer to your face), that's the same thing as adjusting the lens perspective setting in the 3D dialog.
Because Illustrator works in this way, you can add an extrusion to an object using 3D, but if you're looking straight at the object, you can't see it (because the depth is "behind" the object. So in order to see the extrusion, you have to rotate the object a bit (such as the Off Axis front view). But as you mention, this changes the perspective of the text -- you want that to remain straight. But you can't, because then you won't see the extrusion. You can add perspective, which will allow you to see SOME of the extrusion, but I highly doubt that will be what you're looking for. Unfortuanately, you can't select the extrusion and change it's perspective without changing the perspective of the object itself.
The only way to do that would be to apply the extrusion to the object, using the Front view. You won't see the extrusion, but it will be there. Then, expand the 3D effect by choosing Object > Expand Appearance. Then, you can manually select the extruded portion of the object and adjust it to what you need. But this will be EXTREMELY difficult because you will need to select anchor points that are sitting below the object, and also directly below the anchor points for the front of the extrusion.
Oddly enough, this exact kind of effect is something that's far easier to do in CD or FH and if you have those apps available, you might try doing it there and bring the art into AI.