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Hold Pixel Brightness At certain Amount

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Markus Ziegler
Hold Pixel Brightness At certain Amount
on Feb 16, 2017 at 10:15:27 am

Hi.
I ran across a problem in an experiment I just did.

I want to move an black object around the screen and wherever it has been ( = the pixel turned black once) I want the screen to stay black. Until the whole screen is filled with black.

Is there is a way to sample the brightness of an pixel in After Effects?

I believe it can be done using "samplePoint" in an expression.

The only thing I cannot figure out right now, is how to hold the brightness value of a pixel after it has reached a certain amount.

Hope someone can point me in the right direction.

Thanks Markus

markus ziegler
dop_munich_germany
http://www.zieglermarkus.de


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Dave LaRonde
Re: Hold Pixel Brightness At certain Amount
on Feb 16, 2017 at 3:56:33 pm
Last Edited By Dave LaRonde on Feb 16, 2017 at 5:12:38 pm

The effect would look like drawing a black line, yes? There are many ways to draw a line.

If it is a 1-pixel-wide line as you seem to describe, it would take a very long time to make any kind of impact on the underlying image. Just think how long the line would have to be on a 1920x1080 HD image.

And just think how difficult it would be to even see a 1-pixel line in the first place.

Dave LaRonde
Promotion Producer
KGAN (CBS) & KFXA (Fox) Cedar Rapids, IA


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Walter Soyka
Re: Hold Pixel Brightness At certain Amount
on Feb 16, 2017 at 5:26:45 pm

See here:
https://forums.creativecow.net/thread/2/1114556

Walter Soyka
Designer & Mad Scientist at Keen Live [link]
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
@keenlive [twitter]   |   RenderBreak [blog]   |   Profile [LinkedIn]


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