Is there a way to create masks using expression?

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chesco
Posts: 2
Joined: July 22nd, 2012, 2:23 pm

July 23rd, 2012, 11:34 am

I've been looking all over for the syntax to create masks but I can't find it.

I want to create a transition where your video transitions into another by being masked out slice by slice and the slices are all different widths.

Frank
chesco
Posts: 2
Joined: July 22nd, 2012, 2:23 pm

July 23rd, 2012, 12:32 pm

I want to create this effect using expressions.
I made this using keyframes, but it's pretty laborious.

link to vid: https://dl.dropbox.com/u/43613152/test.mp4

It would be cool if I could let the beat of a song control the reveal, thats what i'd really like.
Dan Ebberts
Posts: 319
Joined: June 26th, 2004, 10:01 am
Location: Folsom, CA
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July 23rd, 2012, 4:12 pm

Expressions can't create masks or access their control points, but you could create a bunch of masks and apply an expression like this to randomly control each mask's Mask Opacity property:

minDelay = 0;
maxDelay = 5;

seedRandom(index,true);
myDelay = random(minDelay,maxDelay);
time < myDelay ? 0 : 100

Or, you could use a precomp as a track matte, and inside the precomp you could have a bunch of solids of different widths (or with scale expressions to randomly control the widths) and expressions (like the one above) to control opacity.

Dan
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