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Difference between ZOOM or SIZE

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Digit0
Difference between ZOOM or SIZE
on Apr 20, 2007 at 8:45:43 am


What is the main difference between Zoom and Size. I can get the same effect with either parameter setting.


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jamesinnewcastle
Re: Difference between ZOOM or SIZE
on Apr 20, 2007 at 4:01:32 pm



Generally Zoom will 'zoom' the WHOLE emitter so all the particles zoom together whatever their individual sizes.

Notice that Zoom is only available at the emitter level, at particle level size is the same as zoom so only size is offered.

So you can alter the 'size' of one particle in a multi-particle emitter but the other particles would stay the same - example: the flames from a rocket are the same size throughout the flight but the smoke expands and disappears over the flight - the 'sizes' of the different type of particles therefore change independantly.

If you want to show that you are zooming in on the rocket, say through a zoom lens, then you would change 'zoom' over time. In that case all the particles whatever time they were generated would 'zoom', ie get bigger together.

If you used (emitter) size in the same way the particles would stay the same size as they were when they were created so that later particles are bigger than the earlier particles and the effect would look like the rocket was moving towards you - a very different effect.

I hope that wasn't totally wrong as I'm no expert.

I have found that I approached PI confidently expecting all the different variables to do just what I predicted with a few micro-seconds consideration. What happened then was totally bizarre!! I found that you have to think VERY carefully not only about what you expect from PI but also about your own interpretation of what you think is going on in any effect.

The rocket example is a good one - imagine you are flying past some terroists on the ground and they fire a rocket at you and try to reproduce the effect with PI!! At first I was cursing the program but eventually I realised that I didn't understand what the particles had to do.

James



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Soniclight
Re: Difference between ZOOM or SIZE
on Apr 20, 2007 at 4:12:53 pm

From my understanding and observation:

--- Zoom affects the entire particle field (or all particles). Everything is magnified or reduced together proportionally, including space between particles.

--- Size affects the individual dimensions of each particle, but the space between the center of each particle or particles remains the same; but since the particles are now smaller, there is actually more "empty space" between the edge or surface of all the particles.

To use a solar system analogy:

Zoom down would shrink the entire solar system as one entity, Sun and all planets and all space between them.

Size down would shrink the Sun and all planets but leave the space between the center-point of each one the same. However, since the masses of the planets and Sun are now smaller, there is now actually more empty space between the now-smaller surfaces of each one and all the others.

A bit convoluted, but hopefully useful :)


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Aharon Rabinowitz
Re: Difference between ZOOM or SIZE
on Apr 20, 2007 at 7:01:02 pm

Size scales the size of the particles individually. particles stay in the same position, but get bigger or smaller.

Zoom is used to scale up (or down) the entire effect. Particles are not just scaled, but moved outward (or inward) realitive to eachother and thier emitter. It's particularly useful for point emitters, but also works for the other emitter types, but not necessarily the way you might expect.

You can use this property to animate an effect growing closer to the camera by zooming up over time. Try it with one of the emiters from the Creature library (like Octopus). You'll see what I mean.


----------------------------------------
Aharon Rabinowitz
arabinowitz(AT)yahoo(DOT)com
http://www.allbetsareoff.com

----------------------------------------
Click the link below to subscribe to the Creative Cow After Effects Podcast, and get free AE video tutorials:

http://phobos.apple.com/WebObjects/MZStore.woa/wa/viewPodcast?id=111087911


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jamesinnewcastle
Re: Difference between ZOOM or SIZE
on Apr 20, 2007 at 7:20:10 pm

Ha

I keep learning - no wonder I had so much difficulty with my approaching rocket!!

James


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Aharon Rabinowitz
Re: Difference between ZOOM or SIZE
on Apr 20, 2007 at 7:41:13 pm

OK - the Octopus wasn't the best example. Here's a good example movie that will show the difference:

http://allbetsareoff.com/temp/size_vs_zoom_CD.mov

----------------------------------------
Aharon Rabinowitz
arabinowitz(AT)yahoo(DOT)com
http://www.allbetsareoff.com

----------------------------------------
Click the link below to subscribe to the Creative Cow After Effects Podcast, and get free AE video tutorials:

http://phobos.apple.com/WebObjects/MZStore.woa/wa/viewPodcast?id=111087911


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Digit0
Re: Difference between ZOOM or SIZE
on Apr 21, 2007 at 12:02:54 am

Thanks Aharon for the example MOV file that demonstrates the difference perfectly.


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