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Particle Based Swarm.


Symbolic

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Hi,

This is something that I had worked on long time ago during my studies at NCCA.

People asked me a few times about offsetting the playback of the *.bgeo sequences... so I decided to put together this as a case study with the files and everything.

Some of the expressions and nodes might not be used properly... but at the end it is an amateur experiment :)

Quick Notes:

* Used color attributes to control the speed of the particles.

* Deleted those points that do not behave as I want.

* Exported the points as *.bgeo sequences.

* Imported the points and used the Copy SOP to instance the geometry to each point.

There are two techniques for *bgeo playback offset :

1) Directly use the particle velocity to control the playback speed.

This is can go crazy sometimes. :)

2) Use Sequence Blend to blend between "Slow", "Normal" and "Fast"

This is not that precise, since there are only three speeds... but is more stable.

In this second technique the velocity is calculated to generate 0, 1, 2 and this is used to control the Sequence Blend.

Sample Frames:

<Color Based Particle Behavior>

img1.jpg

<Instanced *BGEO sequences - Technique_1>

img2.jpg

<Instanced *BGEO sequences - Technique_2>

img3.jpg

Here I have used color to check if the Sequence Blend works.

Red objects are moving fast, blue objects are slower.

Sample Video:

frame.jpg

swarm_flipbook.mov

The Houdini Pack (H9.1):

swarm_sys.zip

Thats all. :)

As I said, it is experimental and I am sure there are ways to get more precise results.

:) Use at your own risk.

Thanks to the entire OdForce community!

EDIT: The latest Digital Tutors H9 DVD has a very good section on instancing animated geometry on particles.

But I guess there is not much about offsetting the animations per instance.

Edited by Symbolic
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Sorry, I don't have a time to prepare any examples now but since indeed this is a very common problem, I used to studied it a bit (as most if us). General rule is that if you want to play with your point's attributes depended on time (animation!), use CHOPS.

Whenever you feel the limitation of VEX which is time independent by its nature - jump to CHOPS, process your attributes, go back to VEX, do your stuff, and so on...

You can easy animate any attribute with CHOPs, offset it, whatever. Did you try? CHOPS are much easier then they seems on the beginning. It's just a matter of your understanding what you actually see on graph. Go and try!

cheers,

sy.

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Actually I have a bit of CHOP experience from when I did the Lightwave to Houdini digital asset which is over at the Exchange, so I will try it early next week when I have some spare time. I did suspect CHOP was the answer to many things, including ofsetting instance animation, the meaning of life, getting gold from stone and some other trivial topics. -_-

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