What you should try is to just have the mask at its full size and tween its y property to gradually cover the logo until the solid area covers it entirely.
here are instructions to do a feathered (variable transparency) mask and source files.
Hi guys thanks for the posts, another thing I'm having trouble with is that for whatever reason in my mask layer I have a gradient box going from 100 to 0% opacity that makes the gradient (like what is shown in my above image), but when masking there is no gradient shown, it always simply 0%?
Can't do I do gradients in masks? Or do I have to do something special? In this instance I'm doing frame by frame mask with no animating/tweening.
Any ideas would be great
Also guys I tried
//enable bitmap caching for both movieclips
logo_mc.cacheAsBitmap = true;
mask_mc.cacheAsBitmap = true;
//tell the colored car to use the gradient clip, mask_mc, as its mask!
logo_mc.mask = mask_mc;
but this didn't work for me. That might work only for when tweening/animating a sliding mask? But it didnt work for me using the frame by frame masking I am trying.
You shouldn't need to do frame by frame masking. But you do need to use the cacheAsBitmap commands if you want to use the gradient masks. As far as I know (not very far), fading in a mask in a tween will have broken something in the masking or the tweening or both.