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pixels, motion, and scripting
david van brink // Thu 2007.12.6 20:36 // {after effects}

Particle Halftone

Wikipedia defines halftone as follows:

Halftone is the reprographic technique that simulates continuous tone imagery through the use of equally spaced dots of varying size.

I’m going to use the term more loosely, to mean: Any repetitive visual modulation to suggest a continuous tone image. It’s really quite surprising how our eyes can extract information from such subtle patterns! Even if visual artists have been leveraging this in various ways for thousands of years.

It turns out that After Effects’ Particle Playground can be used for a wide variety of halftoning.

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click for
http://www.youtube.com/v/bL-OZyrK4g4&rel=0&color1=0x3a3a3a&color2=0x999999&border=0

For each of these, the Cannon has been positioned off screen, and its radius set very large. Also, the velocity has been set low, so that mostly gravity affects the particles.

The main trick is to use the Persistent Property Map and Ephemeral Property Map to let the source image, a certain easily recognized half-human, modify various aspects of the particles. You can map each color channel (red, green, and blue) to aspects such as size, rotation, and offset. The Persistent Property Map keeps the modifications when the source image is removed; the Ephemeral Property Map changes instantly and treats a missing image as all-black. For these, it was just useful to have a grand total of six changeable aspects.

One thing I found: Particle Playground renders pretty quickly, even with the 1000 new particles per second that these compositions used. But if you turn on any amount of “particle repel force” — as at the end of the last example — the speed slows way down. But that makes sense; if you have, say, 10,000 particles going, then computing the repelling force involves 100,000,000 potential particle interactions.

Anyway. It sure is fun to krunk out your images! Feel free to download the AE project.

P.S. Dear Adobe, the Particle Playground is grand. It has features that the CC Particle World — which is nice and all — just can’t get close to. But please consider adding more property maps! Six is just enough to get started, but give me 10 or 15 and, whee hoo, we’ll burn some eyes out!

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