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Randomize Opacity within a Shape Layer/Repeater

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Casimir FornalskiRandomize Opacity within a Shape Layer/Repeater
by on Nov 23, 2013 at 9:24:31 pm

Hi there! I've been a long time Creative COW reader, but this is the first time I've posted a question, so I hope y'all can help me out.

I'm trying to animate a nighttime skyline with lights coming on randomly (see image for the idea.) I've built the window arrays using Shape Layers with Repeaters (my preferred method) but I can't figure out how, if possible, to randomize the opacity level of individual shapes within a repeater.

I'd like the windows to "pop on" randomly, and not be uniform (ie, not all lights on each floor would be turned on)

Does anyone know how I could approach this? Is it possible to create an opacity map using a fractal noise layer, similar to what I would do with a shader effector in C4D? I'd really prefer to stay using shape layers and AE for this.

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Brendon MurphyRe: Randomize Opacity within a Shape Layer/Repeater
by on Nov 24, 2013 at 6:53:08 pm

I don't think you can do this with the repeater. To my knowledge there is no way to affect instances individually in that way. You COULD, however, create your windows using the Mosaic effect. It would go something like this:

1. Create a new square solid
2. Add fractal noise
3. Add the Stylize->Mosaic effect. This uses the fractal noise to randomize color value, but keeps each square uniform.
4. Add a grid, invert it, and then set the blending mode to "Stencil Alpha". This is the space between windows
5. Animate the evolution of the Fractal noise

You can then use this solid as a track matte for your orange window color:
-Add a black solid under your mosaic, and then precompose them together. That's your matte.
-Use it as a Luma Matte for an orange solid.
-Precompose those together, and then drop your glow fx on that precomp.

Andrew Kramer does something very similar in this tutorial at 14:24 and 28:04 if a visual would help you:

Let me know if that does it!

Brendon Murphy

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Casimir FornalskiRe: Randomize Opacity within a Shape Layer/Repeater
by on Nov 25, 2013 at 2:23:28 am

Hi Brendon,

I gave this a try and it looks pretty sharp!

Normally I'm a big proponent of shape layers and try to work in those as much as possible, but the inability to affect instances (the way you can in Cinema 4D with cloners) does seem to limit their capability quite a bit.

Anyway, the mosaic method you described is more than adequate for my needs, so thanks a bunch!

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