I want to use the Speed aka Vector pass in the compositor for some motion blur. Currently, it works based on rendering multiple frames. This is time consuming in Cycles. So I am wondering if there are any ways to fake it.
Since the output is a vector, it should just be an RGB or XYZ. Can this be faked with a material? Could you do something like make separate mesh and render it on a different layer with a shadeless material? Or rig up a widget that uses drivers and the position of an object to control a material? Has anyone tried this sort of thing before?
I don't really have enough info on how the speed pass works in order to know what the best method is. Can anyone shed some light on how it works and what would be necessary?