I don't suppose you can animate a matching boolean assemblage? I actually have not tried booleaning in Carrara, though it was the only way I could build some things in Bryce. Could you boolean a solid terrain with an invisible object, say a negative duplicate of the tire pattern, or tread segments? A boned matching negative track assemblage that unrolls behind a tank leaving booleaned tread marks might work. It would not be that hard to synchronise the timing of the two mechanisms.Anyway, if it could be done, it would probably render as slowly as using a displacement animation. It would probably be easiest and fastest to achieve this effect using material channels, as Mark said.