while my 450 frames animation renders, i decided to write that.
if u rendering a still camera aniamiton and u have only 1 object moving in a still 3D backgound, then render 1 frame of the non-animated objects, save it, put it as an envoronment map and hide all exept what was moving and not rendered to the env. map. and render the full animation.
ps: a 4 hours rendering takes me 30 mins with that methhod:D
BTW: add some more rendering tips please:beer: