alpha matte quartz composer

Alpha matte in quartz composer

pho's picture

Hi,

I started using quartz composer recently and I've been exploring it a little bit. However, I didn't find a way of masking objects in the same way I would with an alpha matte in Adobe's After Effects. Does anyone know of a way to achieve that?

I made a video as an example of what i'm trying to do. Here it is: http://img268.imageshack.us/i/ylr.mp4/

Basically, there is a countdown that "cuts a hole" on a square shape.

Thanks