After Effects Compositions of Masks not lining up?

[StevoBow]

Hi Guys, 

I'm a complete newbie and trying to Map my house for a projector Christmas Display.  So I'm using 2 video files.. 1 which is snowflakes falling that will cover the whole house and the 2nd which is a music video that will cover the top section of the house. 

I thought that I had to make 2 compositions up.. 1: The snowflakes masked to the whole house and 2: The music video masked to the area that I want. 

As soon as I combine the 2 comps together the 2nd video is too small and not bright enough.  How do I fix this? 

I've been racking my brains for ages and watching as many tutorials as I can yet I cannot fathom what I've done wrong. 

I've attached some pics so you can hopefully understand what I've done wrong! 

I really appreciate any help I get 🙂

[Roland Kahlenberg]

Copying masks from one layer/composition to another requires both source and target to be the same size for the mask to stay in place - masks do not auto resize/auto-reposition when pasted into a target with a different dimension.

You can solve your issue by using a precomp to scale one of the asset until it perfectly matches the size of the other. You will want to use one asset as a guide while resizing. HTH