simple expression question

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Old 11 November 2012   #16
Originally Posted by merlino3d: I can't download the scene file ...


I reupload the file.
scene file


For now, these particles do have some random motion but just busily jittering back and forth. I want them to have a more smooth dancing looking (full three axes) and if they collide with each other it should be fine for my purpose cause I will have them emitting lights so the collision won't be so obvious. Let me know if my description is not clear!
 
Old 11 November 2012   #17
Hi lxhtin,
what about this scene ?
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Old 11 November 2012   #18
Originally Posted by merlino3d: Hi lxhtin,
what about this scene ?


hi merlino
Thanks for the file!
So did you write the expression for the turbulence field phase attribute?
I think it does help add more randomness!
But when looking at each particle, they are bouncing back and forth the same way repeatedly through the animation. (each moves back and forth along certain line)
I wonder if it's possible to have each particle's moving around their born place randomly in x,y,z. I don't know if there exists a positionPP thing for per-particle attribute that have the function similar to "sphrand " (i guess randmize in 3 axes) as time goes.
 
Old 11 November 2012   #19
Hi Hanny,
just a question, you want the particles to do some like orbit around the original goalPP or move just randomly. And the movement is it an hysteric one or a calm? Anyway I'll try tomorrow ...
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Old 11 November 2012   #20
Originally Posted by merlino3d: Hi Hanny,
just a question, you want the particles to do some like orbit around the original goalPP or move just randomly. And the movement is it an hysteric one or a calm? Anyway I'll try tomorrow ...


your question is RIGHT ON POINT!
i want them to move like orbit around the original goalPP (where they were born), which means they still kind of keep the shape as a whole but not completely stick with that. And they move in a calm way (smooth, not too fast, elegant motion)

Thanks again for your time!
 
Old 11 November 2012   #21
Actually I've found a way to make the particles orbit around his goal, using the goalOffset, but I can't find a way to make it a PP attribute, they are all moving together right now ... :( any idea?

EDIT: can't find a way to make it PP ... sorry
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Last edited by merlino3d : 11 November 2012 at 10:58 PM.
 
Old 11 November 2012   #22
Originally Posted by merlino3d: Actually I've found a way to make the particles orbit around his goal, using the goalOffset, but I can't find a way to make it a PP attribute, they are all moving together right now ... :( any idea?

EDIT: can't find a way to make it PP ... sorry


yea. I searched for goal offset after reading your post. It seems that there is not PP attribute option for this. And I found this link: http://forums.creativecow.net/thread/61/859854
He asked about the similar question I guess :I have got particles moving along a curved NURBS surface using goals and animating the goalU & goalV values.

I am happy with the general result but what I want is the ability to adjust how far above the surface the particles move.

Since i want them spread out over the surface, i cannot just offset the surface, use the offset surface as the goal and hide it. Since the surface is curved, I cant use a static value for the goal Offset. Using sphrand for the goalOffset did not produce good results either.

I would imagine I need an expression to determine the surface normal based on the goalU and goalV for each particle and then offset that particle along the normal."

Or, if it is possible to write some expression of offset based on particleId??
 
Old 11 November 2012   #23
Another option could be to create some deformer or blenshape and deform the goal geometry along the surface normal.
Anyway I've made another test with a softer turbulence ... I hope this can help!
link
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Old 11 November 2012   #24
goalOffsetPP is available once you click on the button in the particle shape goal section in the attribute area. You can creat it with mel but its probably just as easy for you to do it manually. From then it seems to only work as a runtime expression and wont work on the first frame.

You could also, along with the goalOffset, put an expression on the goalTangent which will make the particles move in a side to side direction at a tangent to the surface normal.

I would like to ask what your goal weight is? If it is 1 then that is why you wouldn't have seen particles moving from fields and also might be why they jump if fields are applied with goal weight at 1.

Maybe try set it lower (0.8-0.999) to be able to use fields with a conserve value of 0.95-0.99 (conserve is very sensitive and doesn't need to be lowered that much for particles to lose their velocity over a small number of frames.
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Old 11 November 2012   #25
Hi Daniel, thanks for the help.
I've searched in the particleShape Attribute Editor Goal Weights and Objects but I can't find goalOffsetPP. The options are:
Goal Smoothness
pCubeShape1
goalActive
and then the PP attributes:
goalWeight0PP
goalWorldPosition0PP (witch I can't make works in any way, it just have no effect in my scene :S)
goalWorldNormal0PP
goalWorldTangentU0PP
goalWorldTangentV0PP

I was hoping the goalWorldPosition0PP could works as a goalOffsetPP, but actually I can't obtain anything from it, I just doesn't understand how it works
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Old 11 November 2012   #26
Here is the complete list of particle attributes...

http://download.autodesk.com/global...mber=d30e713376

I have used it so i know it works. I was going from memory so couldn't remember where it was but I've checked and it in the add attribute section next to where goalU and goalV are (under Add Dynamic Attributes->General). It's called goalOffset not goalOffsetPP.
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Old 11 November 2012   #27
Daniel, many thanks!
I've understood! The problem was my expression for the goalOffset: it was the equation of a sphere, but I've forgot to randomize the value for each particle, maybe linking the seed to the particleId. So the particles was moving all together
Thanks!
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Old 11 November 2012   #28
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