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Forums Adobe After Effects ROTOSCOPE ISSUES


  • Kevin Bostic

    August 10, 2022 at 1:23 pm

    I have footage of someone walking through curtains and I want to replace the background behind the curtains with a stock still. At this point, I have already used the pen tool to draw and animate masks around the areas I want to replace with the mode set to Subtract. However, this required at least ten masks of varying sizes and some masks need to disappear and reappear depending on the movement of the subject and the curtain. Not knowing a better way to do this, I animated the opacity of certain masks from 0% ( disappear) to 100% (reappear). But now when I scrub through the footage the whole clip turns black at a certain frame and for all of the frames after. I’m sure this has something to do with manipulating the masks opacities, but I don’t know of any other way to have certain masks remain active while others go inactive. Sorry for being long-winded. Any help would be greatly appreciated. Thanks!

  • Andy Kiernan

    August 10, 2022 at 3:29 pm

    Rather than change opacity, I would just move the mask out of frame, then if it needs to come back in later, keyframe and then move back into place. Not sure what the subtract mode is all about, maybe better to precomp roto’d layer and then duplicate and use as a track matte on your stock still?

  • Kevin Bostic

    August 10, 2022 at 6:54 pm

    Thanks Andy, idk why I didn’t think of that, but it’s a perfect solution. The only reason I set the masks to Subtract was because it was seemingly the simplest way to make the background disappear. But I’m still relatively new to AE, so could you please expand on your track-matte method? Please forgive my ignorance.

  • Andy Kiernan

    August 11, 2022 at 10:07 am

    yes sure. Track mattes are very useful, in their basic forms you use a black or white image to tell the layer below if it’s transparent or not. In your case, to remove the section from outside/ through the door, I would use mochaAE/ basic masks on a white solid layer (turn the layer off, then mask relevant parts with as many masks as needed)… this will leave you with a white shape that fits in the gap where you want your new background. So, place the masked sold layer above the background and use the luma matte option (to the right of the transfer modes), This tells the BG to only display where the layer above is white.

    Hopefully that makes sense!

  • Kevin Bostic

    August 11, 2022 at 4:45 pm

    Thanks for the info! This is all very helpful.

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