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  • After Effects and Masks

    Posted by Scott Thomas on June 1, 2009 at 7:14 pm

    Learning Video Editing, so forgive me if this is obvious to most.

    I am working on a video template for a weekly video we shoot here at the firm. The one thing that is giving me the most trouble is masks.

    I’ve created a simple rounded rectangle mask for the images we display as our talent is speaking. Copy/pasting the mask onto new images works great _IF_ the new image is the exact same size as the original.

    If I attempt to resize the image that has a mask, the mask resizes also. Surely, there is a way around this.

    Any help is greatly appreciated. I have spent half of the day searching for this solution.

    //Scott

    Theo Brown replied 13 years, 11 months ago 4 Members · 5 Replies
  • 5 Replies
  • Adolfo Rozenfeld

    June 1, 2009 at 8:11 pm

    There is a work-around.
    Before pasting the mask, select the target layer and Pre-Compose it (Layer > Pre-Compose). You’ll see a dialog that gives you two options – in this case you, want the second one.

    Pre-Composing means: Take the layer(s) I selected, cut them from the Comp I am in, create a new Comp that is nested inside this one, and paste the selected layer(s) inside that one.

    So if you paste in the Pre-Comp (ie, from the main Composition) the mask will fit perfectly.

    But what if you want to scale the image inside the mask? The original layer still has is its’ own scale property. If you double click the Pre-Comp, you’ll go inside the Pre-Comp and you’ll be able to edit the orginal layer’s scale.

    Why are we doing this?
    Because After Effects has a specific order for processing. Transform (for example, scale) always is done after masks, so when you scale down a layer, you’re scaling down them masks.
    When you Pre-Compose a layer, you make sure that everything inside is calculated before. So, the layer inside the Pre-Comp is scaled, then the whole Pre-Comp is masked.

    But, you say, if I do that, I can’t see its’ relationship to the mask as I scale it down!

    Here’s when you can get all fancy and impress your friends.

    If both the parent Comp and the Pre-Comp are available as tabs in the timeline (ie, they are both “open”) you’ll see you can enable a lock for the parent Comp in the upper left corner of the Comp panel. If you enable that lock, you can switch in the timeline to the Pre-Comp tab, adjust scale as you see the results in the parent Comp (don’t try to adjust it directly in the Comp panel, just drag the scale property in the timeline).

    Too complicated?

    Adolfo Rozenfeld · Adobe

  • Michael Szalapski

    June 1, 2009 at 8:23 pm

    Create a solid the same size as your comp. Put a mask on it. Use that layer (and as many duplicates as needed) as a track matte.

    You could also create a layer in Photoshop and use it as a track matte. You can even do this in your editing app rather than doing it in After Effects, that way it can be part of your edit.

    – The Great Szalam
    (The ‘Great’ stands for ‘Not So Great, in fact, Extremely Humble’)

    No trees were harmed in the creation of this message, but several thousand electrons were mildly inconvenienced.

  • Scott Thomas

    June 2, 2009 at 2:16 pm

    Works perfectly. Thank you!! This had been driving me nuts.

  • Adolfo Rozenfeld

    June 2, 2009 at 7:58 pm

    This doesn’t work just for transformations and masks.
    It’s a way to alter the rendering order in any case in which you may want to do so.
    For example, it’s not the same blurring a masked image, than masking a blurred image. The former is the default processing order in AE (Masks, then Effects). To achieve the latter, apply a blur effect to your layer, then Pre-Compose and mask the Pre-Comp.

    Adolfo Rozenfeld · Adobe

  • Theo Brown

    May 31, 2012 at 2:14 pm

    I just ran into this issue as well; why can’t you just scale the image inside the mask when you have the mask applied? I.e., scaling the image also scales the mask, which is not what I want.

    Since the pan behind tool works to move the image within the mask, why isn’t there an easier solution to scaling within the mask besides making pre-comps?

    thanks!

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