• Adobe After Effects

  Cutting out video?

  Posted by Alex Kuzelicki on April 5, 2006 at 10:00 am

  Hi,

  I’m pretty new to After Effects though I’ve used different compositing programs in the past. Prepare for some dumb questions ahead but, if I don’t ask, I’ll never know (without lots of sweat and tears… maybe even blood).

  I used to use a compositing program that allowed you to actually ‘cut-out’ sections of a video and paste them, resize and distort them as a separate element over the original video. That is, the new element was encased in a selection that you could manipulate independently.

  Could I do something like this in After Effects? For example, say I wanted someone’s head to grow really big independent of his body. I’m guessing that I could duplicate the layer as a background, and then mask out the head area of the foreground layer. Which could then be sized up… but how do I size up the mask at the same time? Or would it just size up automatically if it’s connected to the ‘head’ layer?

  Or is there another way to ‘cut out’ isolated areas of a video frame, to be manipulated over the original?

  Thanks in (hopeful) advance.

  Regards,

  ALEX KUZELICKI

  Ryan Hill replied 20 years, 1 month ago 2 Members · 3 Replies
• 3 Replies

• 

  Ryan Hill

  April 5, 2006 at 4:09 pm

  I believe the mask will scale up with the layer. The properties of a layer are listed in order, and transformations are below masks, so it is applied afterwards.

  There are plenty of ways to cut out part of a layer. Off the top of my head, you can use vector paint, you can use another layer as a track matte, you can apply a key filter, there’s probably hundreds of variations on this.
• 

  Alex Kuzelicki

  April 5, 2006 at 5:12 pm

  Thanks kindly for your reply,

  In the meantime, I’ve been doing some tests and have indeed discovered a few different ways to ‘cut out’ video… and I’m very happy that the Mask does ‘stick with’ the layer no matter what transformations occur.

  I’d love to know how to use a Video Matte though. I remember being able to use a black and white (rotoscoped) video as an alpha channel but am not sure how to do it in After Effects. As I recall, there were two main uses: 1) To superimpose a moving subject over a background and 2) Using the alpha channel as a ‘shape’ filled with some other video.

  How can I do these in After Effects? Would be much appreciated.

  Thanks,

  ALEX
• 

  Ryan Hill

  April 5, 2006 at 6:35 pm

  I think what you are describing is known as a track matte in AE.

  https://www.editorsguild.com/newsletter/MarApr03/tip_ae_track_mattes.html

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