I love this trick.
You want to make a layer disappear and reappear? but hate creating all those key frames in the visibility channel for each layer to hide?
Just put a a vector layer in your group or bone layer. Make sure it is the last layer in the layer palette. Put a solid color shape, like white, on this layer. Release the points so it won't move with any bones you have. Make it immune to camera motion.
when ever you need to hide a layer, just drag it below that layer in the time line. BINGO! It's hidden.
If you have your background layer outside of the group layer this won't work. Another trick would be to set the masking of the parent bone layer to "Show All". Put a solid mask as THE FIRST LAYER so it won't effect anything below it. Set the masking to "Subtract from mask".
Now when you want to hide a layer, drag it ABOVE this mask layer. It is hidden now by the mask.
-vern
Use animated layer order to "hide" layers.
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