Hi Nicolas > I use keyframes and the compositor window to create a vertical scrolling > (end credits) from a still picture. However, the scrolling speed isn't > constant. I assume that's due to the fact that interpolations between > keyframes are made with a bezier curve.
You are correct; the bezier curves used are forced to have zero slope at every keyframe. This means you get "smooth" starting. While this can be good in certain circumstances it is a pain for others such as the credit example you mention. At times you do want keyframe interpolation to use something else which produces constant speed between keyframes. > Is there a way to use a linear interpolation instead of the bezier > curve? That way I would be able to scroll my end credit picture at a > constant speed, wouldn't I ? With linear interpolation the speed would be constant, yes. This is actually an aspect to Cinelerra which I noticed with annoyance about 18 months ago for the same reasons as you - I was scrolling credits and noticed they were *much* slower at the start and end than in the middle. It is most irritating. Unfortunately cinelerra (both vanilla and CVS/SVN) do not have alternative curves available (at least not when I last checked CVS/SVN about a year ago). I would offer to look into this myself but I am currently far too busy with other FOSS projects and life in general. The workaround I came up with at the time is a bit fiddly but with patience you can get reasonable results. I arranged things so that the approximately linear portion of the bezier curve (ie: the bit in the middle) corresponded with the part of the timeline where the credits were to scroll. For my project this meant starting the scroll about 30 seconds before the credits and ending it 30 seconds after the credits. The starting and ending Y values were adjusted so that the credit graphic just became visible and just finished at the appropriate points in the timeline. This last requirement is where things get a bit fiddly - it's pretty much a trial-and-error thing. Assuming the credits are at the end of the movive, an unfortunate consequence of this is that your final rendered movie has a blank, silent portion tacked onto the end which lasts lasts for 30 seconds (or whatever runout time you needed for the curve in your particular project). To avoid this blank silent stuff at the end of the render the easiest thing to do is to select from 0:00:00.000 to the point where the credits/movie material ends and then choose File|Render. To select such a long timespan accurately I find it best to type the times into the selection span boxes under the timeline. I hope this helps. Regards jonathan _______________________________________________ Cinelerra mailing list [email protected] https://init.linpro.no/mailman/skolelinux.no/listinfo/cinelerra
