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# constraining a turbulence field...

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 constraining a turbulence field... on Aug 1, 2005 at 6:01:03 pm

Is there a way to make a turblence feild only move particles on the x and z axis (not moving them on th Y axis)?
thanks

 Re: constraining a turbulence field...on Aug 1, 2005 at 7:46:01 pm

I don't think so, Chad. What about a runtime expression along these lines:
vector \$pos = particleShape1.position;
particleShape1.position = <<\$pos.x, 0, \$pos.z>>;
I don't know if that would work for whatever you've got in mind.

Good luck.

-Steve

 Re: Clarifying...on Aug 1, 2005 at 7:47:46 pm

Sorry, I should have specified that that expression would work in tandem with a Turbulence field--it's not a replacement for one (obviously).

Although, hmmm, on that note, you could perhaps create your own turbulence field with an XY noise function and MEL, right? That might be a cleaner approach.

-Steve

 Re: Clarifying...on Aug 1, 2005 at 8:11:34 pm

but would the noise make a smooth path? or would the particles pop all over the place from frame to frame?

 Re: constraining a turbulence field...on Aug 2, 2005 at 1:43:29 am

Hey steve, this expression seems to do the trick. I didn't think i could overide the position once the turbulence was kicking in, but looks like i can.
thanks for the tip

 Re: constraining a turbulence field...on Aug 2, 2005 at 3:14:55 am

Drag fields can be set to affect only one direction vector. So you could have a large magnitude drag field for the y direction, and a turbulence working. That would make the turbulence field only move particles in x & z since the drag would negate vertical movement.

 Re: constraining a turbulence field...on Aug 2, 2005 at 2:04:41 pm

Sean, I tried that too, but I wasn't happy with the results. The particles seemed to drift vertically anyway, despite the drag field.

Turning the drag field up higher resulted in runaway oscillations that made the particles shoot off to infinity. Maybe this behaviour has been cleaned up in more recent versions, though.

Chad: sorry, I failed to clarify again. When I talked about using an XY noise function, I was thinking of applying it to the particles as a force, not writing it directly to their positions. In that case, the motion would remain smooth.

Cheers guys.

-Steve