After Effects help!!!

[photographique]

Hi guys,

I want to ask that how to make this -

an animation with black background, and an rotating ring, in which the ring is pre-made, and I have already rotated it.

As the ring rotates it is suppose to reveal something through the space inside the ring, which means that when the ring is not totally horizontal something is revealed in the space inside the ring, but whatever revealed is not rotating with the ring.

I am having trouble revealing it but at the same time keep the surrounding of the ring black.

Anyone care to help me on this?

Thanks in advance!

 

[DXNMedia]

You need to create an animated matte or mask to slowly reveal the part that you need to reveal, then embed the mask/matte information as an alpha channel within your movie file.