angular crop

[snerd]

Hello.

I am attempting to create a continuous animation of a ring either appearing or disappearing (sort of like PAC-man death, but probably only in one direction, rather than the mirrored effect that PAC-man has).

Obviously this can be created in however many frames by an animator.

It seems like it would be smoother and easier to do, however, using a pixel-shader.

Does anyone know if such a shader exists already? Or is anyone interested in attempting to make one?

Thanks.

[snerd]

Apparently this effect is called clock wipe, or radial wipe.

Anyone know how to achieve it?