Tuesday, August 29, 2006

smooth scrolling credits for Cinelerra

An easy way to simulate scrolling credits is to use a very long jpeg or png image and use camera automation in order to scroll from the top part of the image all the way to the bottom of it. The one issue that has been called out on the Cinelerra boards is that the default camera automation is done using bezier curves. So, what'd you'd see by taking the defaults is that the scrolling would quicken at the beginning and the end of the automation, but be somewhat linear in the middle. The steps below show how to straighten out the curves in order to make the scrolling linear from beginning to end; in other words, a constant rate of scrolling all the way through the automation. Thanks to Nicolas from Paris for the directions!

- turn on the X and Y camera position indicators in the View menu
- click on the "Generate keyframes while tweaking" small key icon in the Timeline or Compositor
- for the scroll beginning, modify the Y position of the camera, in the compositor window. You can also click the "?" icon to enter the value directly
- at the end of the scroll, click and then I go back 1 frame to edit the Y camera position again
- go back to the main window and select "Camera Y" in the view menu.
- type "Alt-F" to modify the "Camera Y" green line height to see it entirely on the video track
- click on the start keyframe while typing "CTRL" to modify the keyframe curve slope
- do the same for the end keyframe in order to get a straight line between the start and end keyframes

After tweaking the settings, the scroll speed becomes nice and linear.

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