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sampleImage and Matte or cropping comp
I have had a look on the internet and I have been looking for a way to use the sample image expression in After Effects and have it either crop the comp, mask or define the boundary of a image sequence based on the life of the comp amd its colour extents.
Basically anything that’s not black in a moving fire and then have it create a 4 sided shape showing the extents over the life.
Any ideas on what channel to plug it into or variable to look at would be great.
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1 Reply
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I’d probably do it with a script that uses sampleImage() to animate a mask.
You could also kludge something together with expressions that, for example, use sampleImage() to move four solids around in a precomp which you could use as an inverse-alpha track matte for the fire layer. It would be ugly and slow, but it should work.
Both of these methods would depend on you being able to define the level of black you want excluded.
Dan
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