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Old 07-14-2008, 01:18 PM   #1
Benjamin Jürgens
CG Artist
NHB Düsseldorf
Dusseldorf, Germany
Join Date: Apr 2008
Posts: 34
Controll the random spin of particle Instaces?

Hey all,

I'm building a space scene right now. It's a POV flight through a asteroid field. I realized it over a Particle field, the instancer and a little PP Array Attribute.

Under Creation it's:
Asteroiden_GroßShape.RandomSpinPPBIG = rand(-1,1);

under runtime before dynamics it's:
float $spin = Asteroiden_GroßShape.RandomSpinPPBIG;
Asteroiden_GroßShape.BigAsteroidRotation += 0.6*$spin;

The asteroids are now spinning randomly in all 3 possible spinning directions. The result is a really strange rotation movement. It looks like a force is changing the rotation direction from time to time. In space as far as I know such a force doesn't exist, so i want to get rid of it.

I'm new to Maya Dynamics and don't really know how to get the asteroids spinning in one or two directions only.

Hope my english is good enough to make you understand what's my problem.

Old 07-14-2008, 06:42 PM   #2
The Red Scarlet One
CarlRiver's Avatar
Reinhold Rittinger
Join Date: Jul 2006
Posts: 130
the way I would go about this would be to create a creation expression that assigned a random spin-vector to each particle:

RandomSpinPPBig = sphrand(1);

The value in the brackets controls the speed of the rotation. Then as a runtime-before expression you could write something like this:

BigAsteroidRotation += RandomSpoinPPBig;

This should about do it and should work fine.

And a small tip: don't use non-standard characters like ß or ä,ö,ü in Maya.
Old 07-15-2008, 12:11 AM   #3
Benjamin Jürgens
CG Artist
NHB Düsseldorf
Dusseldorf, Germany
Join Date: Apr 2008
Posts: 34
Thank you!
I'll try it tomorrow.

greezt from Cologne
Old 07-15-2008, 12:11 AM   #4
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