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rcronin
09-03-2008, 04:44 PM
Hi all,
I have some instanced particles with a curved poly surface as a goal. Particles moving to reach the PP goals. My position is worldPosition and AimDirection is worldVelocity. What happens is that random instances are popping on their axis to a different up direction as I play the simulation. e.g in 1 frame an instance will 'pop' rotate 40 degrees on the z axis for no reason.
Has anyone had problems keeping their instance rotations stable as they try and reach a goal?
Any ideas? Thx rY
p.s. no collisions, just sketch particles, make poly a goal, goal .3, goal smooth 4, conserve .1.....
Aikiman
09-04-2008, 08:19 AM
Sounds like the object you have created to be instanced is not facing the right way. Make sure your object is facing down the x axis and freeze tranforms at world zero first before you make it an instance.
groblus
09-04-2008, 09:48 AM
is this flipping occuring only at the beginning of the move and at the moment they stop ?
It might be because worldVelocity is changing rapidly when they start to move or stop (pointing in an akward directions). Also if you're using goalU goalV to make those particles move there also might be some problem with the uv layouting, hard to say without looking at your scene
rcronin
09-04-2008, 09:07 PM
Hi Aikiman, yeah my instance object is zeroed and facing positive X.
Groblus, yes I'm using goal u/v rand (0,1) to generate random goal position but it's basically just a flat plane with a lattice applied to bend it a bit. Tried nurbs and polys but the same thing happens -

instances travel towards their goals but random instances pop on their axis'. I'll attach a scene here in a moment...

-that being said, will deforming a surface a lot change it's vertice uv info so much that it would be hard for a particle's rotation to read?
Aikiman
09-04-2008, 10:31 PM
Maybe not so much the UV info but perhaps more so the normal info of the surface, do you have an aim up axis?
rcronin
09-04-2008, 11:43 PM
Hi guys,
Here's a scene, play it through a few times and you'll see random pops in the cylinders even when they are not close to edges. P.S. maya 8.5
*which aimUp axis would you recommend?
Aikiman
09-05-2008, 09:53 PM
On the surface it looks as though the velocity is changing because if you make the aim direction any other value it doesnt do it. But if you make the particles numeric and view worldVelocity I cant see any drastic change at all in velocity to cause the flipping. A hack could be to create a seed(id) in creation and turn the lifespanPP to 0 for the offending particles.
Aikiman
09-08-2008, 08:01 AM
Make AimWorldUp worldVelocity also, that solves your flipping problem.
rcronin
09-08-2008, 04:14 PM
Ah! You're kidding right?
I could have sworn that I played with aimWorldUp. But sure enough, solved. Thanx a bunch. rY
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