object transparency masking? [solved]

[SteveTX]

I am interested in making parts of image and graphic objects transparent so the background shows through them.

Layer 3 - The Mask
Layer 2 - The Object
Layer 1 - Gradient Background

OR

Layer 3 - The Object
Layer 2 - The Mask
Layer 1 - Gradient Background

When the (invisible) mask covers pixels of the object, only the background should show.
It is my intention to animate the mask so that the object begins to appear on the screen although already predrawn.

Can this be accomplished with blends? Is there a better way?

[Simon]

Hi Steve,
Is this just a dissolve? Or something fancy like blinds?

Simon

[SteveTX]

Simple. Not even a mediary stage between the blend, either it does or doesn't show the pixels, no alpha needed. No sophisticated transition, the mask could be described by a growing/shrinking/moving rect.

[SteveTX]

solved. Instead of setting visible the object, use show or hide "with visual effect".