Actionscript3 alpha masking?

Question

I was trying to apply a spotlight effect on a google map application. Specifically, I draw a circle that follows the mouse and set it as a mask over the map. The problem is

Answer 1

To use alpha masking you need to do the following:

• apply the mask using actionscript, not the Flash authoring.

i.e. googleMap.mask = alphaMask;

• turn bitmap caching on(cacheAsBitmap = true);

That should do it.