This not an easy task but it can be done. Like most things in 3D animation, this will require deliberate, planned choreography. You'll actually need to create an animated texture map of progressive tread tracks in a 2D program that supports animation (Painter, Adobe Photoshop CS3, Apple Motion) This completed animation file will then need to be imported into the color and bump channels as a mixer control for the ground texture map or placed into the displacement channel. If it goes into the displacement channel, expect a significant speed penalty during render. You've got some "wiggle" room or error room available during the Carrara motion because the tank can hide a portion of the tread animation so it doesn't need to be super precise. However, the tracks will need to be perfectly spaced in their side-by-side relationship. If you choose to put the animated map in the displacement portion of the texture, you will have very, very little room for error. If you're doing a single tank, there is a way to progressively swap one ground texture for another so you could actually "paint" the ground texture, one with treads, one without, and then progressively exchange them as the tank moved across the scene. Professionally, things like this are often disguised by dust clouds in post production or carefully planned camera moves the severely limit the time "on screen" of the ground. That way precision becomes less of an issue. I see the treads as being a challenge too. ;) Mark