I'm pretty new to after effects CC and I'm currently trying to do a basic masking effect to create the illusion of a crowd by layering footage one person over and over again in different positions on the frame. When I try to mask out one of the layers the rest of the footage is white outside the mask instead of being a transparent box that shows the figure in the layer.
I've been following a few tutorials and I noticed that I have an icon missing from the top of the composition window and I'm wondering if that could solve my problem.
I screen shotted the tutorials interface that has the icon I'm missing. If that link doesn't work (i'm not sure if it will, I'm new to this site's layout) it's the first icon to the left of the composition window. It looks like two boxes with one being transparent coming out diagonally from one.