How to combing rotobrush with a mask

[patrickh27764550]

I have a mask that is a simple polygon on the top half of the screen.  Towards the end of the clip, an odd shaped object comes into view and crosses the mask line.  I want to keep this object out of the mask.

Idealy I would create a new mask of the object with the rotobush and subtract it from the polygon mask, but from what I understand, rotoscoped objects can't be turned into masks.

Is there a way to do that?  Maybe with the Track Matte?  I'm unfamilar with the Track matte at this time.

Thanks

[Sterphy]

It's a little unclear what you're specifically asking without seeing, but a good substitute for using masks on rotod objects is using shape layers - just draw and animate the path as you would a mask and use track matte. 

[patrickh27764550]

Honestly, I figured out how to handle my situation 20 mins after I posted my question.

I have a video I made at the beach. I’m trying to change the color of the sky. Since the ocean color blends into the sky, I just masked the sky using the pen tool with a feather and tracking the bath

A boat comes into the view, the boat has jagged edges, and it’s moving. I want to use the roto-tool to subtract the shape of the boat from the mask of the sky.

I figured out, 20 minutes after my original post, is to Roto the boat into its own layer and place that on top of the sky layer.

[Rick Gerard]

It sounds like you are trying to keep the top of the boat in the sky. If that is the case, you can draw your mask so that it keeps the water, go to the Paint Workspace to make roto easier, open the footage in the Layer panel, Rotobrush, return to the Comp in your standard workspace, then reveal all the properties of Rotobrush in the timeline and click the pluss button at the bottom to add in the mask.

This is what the workflow looks like: