Wow, this is serendipitous. I'm a newbie, working my way through Real World Bryce and yesterday I did a tutorial on animation, 3 seconds long. The sky changes from blue to purple, with pretty cumulous clouds. When the animation played, the clouds were whizzing by like time lapse photography--annoying! So, thanks, Akril, for asking teh question and thanks, Martin, for answering it. I'll try that.