Can I create a mask path using points from other masks?

[Snaileb]

I feel like this should be possible using an expression but I'm not very good with expressions yet... 

I have a footage layer in a comp. On that layer I have created three masks. Each mask has only one point. I have used each mask to track a different moving object in the footage. 

I want to have one mask with three points, where each point is one of the (tracked) points from the other three masks.

Does that make sense? Maybe I need to first apply the tracking data from the three masks to nulls, and then draw the position information for the ultimate mask from the three nulls? 

I've found a YouTube tutorial where somebody uses a .toComp expression to apply the position of a point on a mask to a null. And I've seen a separate tutorial where a createPath expression is used to define points on a mask. I've tried to combine them but I get lost... 

Alternatively if there is a way to just start with one mask but have each point on the mask be tracking those separate moving objects, that would be even easier... But it seems like all the tracking methods want to treat the points on the mask as if their movements are related to each other, which they are not. 

[Dan Ebberts · Accepted solution]

I you have a layer with 3 single-point masks, and you create a 4th mask, you could use an expression like this for that mask path to incorporate the points from the other 3 masks:

p1 = mask("Mask 1").maskPath.points();
p2 = mask("Mask 2").maskPath.points();
p3 = mask("Mask 3").maskPath.points();
p = [p1[0],p2[0],p3[0]];
createPath(p,[],[],false)

[Snaileb]

Thank you so much!! Works perfectly!!