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Forums Adobe After Effects Expressions Matte only over items of a specific color?

  • Matte only over items of a specific color?

  • Jacob Crocker

    June 11, 2021 at 7:05 pm

    Example scenario:

    I have 4 boxes. Box 1 is blue, Boxes 2 & 3 are a specific color of red and Box 4 is green. I would like Box 1 (blue) to only be visible when overlapping a red box. If Box 1 overlaps Box 4 (green) nothing happens.

    My question: Is there a way I can matte a shape so that it is only visible when it overlaps a specific color? Essentially like a “Set Matte” effect that is driven by an RGB hex code rather than a layer’s bounds.

  • Filip Vandueren

    June 14, 2021 at 2:59 pm

    – create a solid in the complimentary color of red (dark green) above your blue box

    – on that solid, use the effect “Calculations” to composite copies of your red and green boxes layer onto that green solid. (if the other boxes are on multiple layersn use mulitiple calculation effects),

    – add the effect “Keying > Color Range” to key out the exact color of red your need.

    – add channel > Invert set to “Alpha”

    – use the result as an alpha matte for your Blue Box.

    It will only show up on top of the shade of red that is keyed out.

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