I know that I have seen a tutorial on this, but I can’t remember where . . . :o
I need to illustrate (toon style…) that air flows through a pipe system and warms up as it does so. I want to do this by (a) laying a gradient blue-to-red texture over the pipe, and then (b) animating stylized arrows that run along the pipe, either on it or a short distance from it … these arrows also changing color as they travel.
Yes, I can piece together how this can be done. But, I know there was a really nice tute on this … somewhere …