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After Effects Spline Tricks, Part 3
Animated splines and Auto-trace
In Spline Tricks Parts 1 and 2, we looked at an overview of Auto-trace (an easy way to create splines for masks) and how to use some of those splines as positional data. While there are some advantages to using Auto-trace in some instances, other uses may not be so "press and play." So, in this latest installment in our Spline Tricks series, we'll examine some of the obvious and not so obvious issues and explain some fixes that may help you to work around the problems.
If you haven't read the first two parts regarding Auto-trace, check out the earlier scribblings here:
Although Auto-trace can be a fun, and sometimes productive tool to use, it is still hampered by the limitations of After Effects' pixel searching and tracking abilities. I don't mean to say the tool is defective in any way, but in some cases, pixel data is too slim to define. Other times, Auto-trace cannot anticipate whether or not more pixels will be added, requiring pre-roll or post-roll spline data. Auto-trace does a pretty good job with the data it sees, creating multiple mask shapes--hundreds if necessary (I've successfully created 295 separate mask shapes on a single layer)--but it does trip and fall occasionally.
Here is are some examples of how it works well, and not so well. Animated Auto-trace does work
The first animated clip to be traced is a 3D render that came directly out of Maxon's Cinema 4D, a simple animation with a corresponding alpha channel. The logo spins around the Y-axis in the center of frame.