I'm fully aware that you through using fades or a composite envelope you make a total image come or go.
However I want to produce another effect that I haven't been able to work out how to do.

I have an image (let's say a tree) which I want to progressively expose vertically as I move down the time line.

So...I start off with the bottom of the image (the ground and the trunk) exposed and then, sort of like a fade in, progressively more of the image vertically is exposed (branches and leaves) until eventually all of the tree exposed.

Any ideas on how I can do this?

Renton

There's always several ways to do anything, and probably others will chime in with others. Two I can think of off the top of my head:
Best: Use a mask. Put your tree on the top track. In Pan/Crop apply a mask. Animate the shape and opacity.
Fast and Easy: Use a transition. Duplicate the track with the tree, make the tree zero opacity on the first track, slide the second track over the first for the amount of time you want the tree to appear, apply an Iris transition roughly the shape of the tree (or just a bottom up linear wipe). Use a broad feather.

Thanks Rainer...a linear/bottom-up transition did the trick.

Found I didn't need to duplicate the track with the image...just used the 'transition' as an animated fade-in over the image.

Exactly what I was after. Looks great and illustrates precisely the point I am making.

Thanks again. Appreciated.

Renton