• Adobe After Effects Expressions

  Finding boundaries of a movie

  Posted by Nick Chambers on June 13, 2011 at 4:09 pm

  Hey,

  I have created an asset for a game and I want to clip the regions to make it as cheap as possible.

  For example. If you had a flame effect rendered out of ‘FumeFx’ and there is a decent amount of dead space. Is there a way to either clamp of find a complete ‘boundary’ in the movie.

  Even if it’s colour based or script?

  Ta

  Nick Chambers replied 14 years, 11 months ago 2 Members · 4 Replies
• 4 Replies

• 

  Dan Ebberts

  June 13, 2011 at 4:38 pm

  I’m not sure exactly what you’re asking, but you should be able to craft a script that could temporarily apply the sampleImage() expression to determine the extents of your asset’s non-zero-alpha area , for example. Then it could create a mask, or precompose to that size. I don’t know if anything like that already exists, but it should be possible.

  Dan
• 

  Nick Chambers

  June 13, 2011 at 4:56 pm

  Yeah it sounds like we are almost on the same page.

  I am trying to create a mask or layer that covers the boundaries of movement. I have used auto-trace so far and it has way to many points.

  Maybe a better way of explaining it – if a flame was on a black background moving around for 500 frames. I would like to create a bounding box that covers the movement of the whole animation.
• 

  Dan Ebberts

  June 13, 2011 at 5:04 pm

  You should be able to do that with a script using a sampleImage() expression to check the extents at each frame. It’s not trivial, but it should be pretty straight forward.

  Can
• 

  Nick Chambers

  June 13, 2011 at 5:13 pm

  Thank you for your help guys

  That should be plenty for me to hunt the inter-web and write something that should do the trick.

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