simple expression question

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  11 November 2012
Question simple expression question

I'm new to expression. And I've been working on a thesis project which needs a little bit of expression knowledge. Basically I want to create a volume of balls moving in a shape while each has their own random motion. So I have the particles emitted from a volume mesh and goal to it. I use .goalU=.parentU/.goalV=.parentV to distribute the particles. I deform/animate the mesh and hide the mesh to have the particles move in the way I want. Now, I need to find a way to make the particles each has some motion within their own space instead of just stick as where they were born. I searched for lots of posts but still cannot find the right one. I tried to use gauss function but it doesn't add to much randomness and looks jittery. I also try to write some expression with goalU, goalPP, goalOffset... but I was not able to make it look right.

I will REALLY REALLY appreciate it if anyone can help me with it. THANK YOU!
 
  11 November 2012
Have you tryied to apply a turbulence field to the particles?
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  11 November 2012
Originally Posted by merlino3d: Have you tryied to apply a turbulence field to the particles?


yes I did, but it didn't do much to the particles
 
  11 November 2012
Originally Posted by eddgarpv: Take a look on this thread and post #4 : http://forums.cgsociety.org/showthr...p?f=86&t=789536


thanks for the link!
I played around this afternoon and right now several particles are crazily moving while some are moving a little bit. I guess it could be the shape of my volume mesh. I tried to tweak the numbers but haven't find the solution.

I attach the scene file here (hope it could be open):
scene file
 
  11 November 2012
Well, "conserve" is a bit too high but you probably mean some particles are "jumping" from the middle of the model, right?
Take a look on the expression and your UVs.. your particles are based on the UV shells and that means you could stitch some shells to get a smoother transition..

edit: grammaaarrr

Last edited by eddgarpv : 11 November 2012 at 12:24 AM.
 
  11 November 2012
Originally Posted by eddgarpv: Well, "conserve" is a bit too high but you probably mean some particles are "jumping" from the middle of the model, right?
Take a look on the expression and your UVs.. your particles are based on the UV shells and that means you could stitch some shells to get a more smooth transition..


Thanks for the fast reply Edgar!
I think I get what you are saying, never really thought about the relation between its uv coordinates and particle behavior. Since the particle goalU/V is based on the map, there would always have some jumping caused from the seam cut, right? Or having stitch shells would help a lot, I have to look into that.
 
  11 November 2012
Originally Posted by lxhtin: Since the particle goalU/V is based on the map, there would always have some jumping caused from the seam cut, right?


That's right. Probably you could use another object for the particles only - with a simpler uvs.
 
  11 November 2012
Originally Posted by eddgarpv: That's right. Probably you could use another object for the particles only - with a simpler uvs.


Yea. But I kind want the balls stay in that shape as a whole. Cause later on I have some more complex animation of the mesh. I have rigged the mesh and finish the deforming animation. I just feel there must be a way to do this effect without a too complicated approach. All I want is adding some randomness/ turbulence effect to the particles. But maybe things are not as easy as I thought.
 
  11 November 2012
please
if anyone has some thoughts about the approach, please help me out. It doesn't need to be doing expression, as long as creating this kind of effect. Thank you!
 
  11 November 2012
make sure you don't have extremely low masses on your particles, they should have mass that is a reasonable range for all of the particles. if you have particles that are moving much slower than others, a mass that is close to 0 is usually the culprit.
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  11 November 2012
Originally Posted by stooch: make sure you don't have extremely low masses on your particles, they should have mass that is a reasonable range for all of the particles. if you have particles that are moving much slower than others, a mass that is close to 0 is usually the culprit.


I just went to the per-particle attribute and create the expression for mass. I used a lower mass=0.03 and it actually add some randomness to the motion! I think the turbulence is creating effect now, maybe my old default mass was set too high?

But the particles still have an 'attached" feeling, looking like they are always bounded with my invisible mesh shape. And their motion is more like waving back and forth in a certain way instead of randomly moving around their born position. I wonder if there is a way to have them do that through creating expressions or using plug-in. I've been looking for "flocking" 'boid" maya plug-in but still not successful.
 
  11 November 2012
basically when a particle has extremely low mass then its fields are not having as much effect on it. if you have fields at extremely high settings then that would explain how you gain more control with less mass.

if you want your particles to be controllable, setting exceptionally low conserve helps alot too. then your particles basically follow your fields exactly.
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  11 November 2012
Originally Posted by lxhtin: thanks for the link!
I played around this afternoon and right now several particles are crazily moving while some are moving a little bit. I guess it could be the shape of my volume mesh. I tried to tweak the numbers but haven't find the solution.

I attach the scene file here (hope it could be open):
scene file


I can't download the scene file ...
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here's my blog, you'r welcome to visit and comment! :)
 
  11 November 2012
Originally Posted by stooch: basically when a particle has extremely low mass then its fields are not having as much effect on it. if you have fields at extremely high settings then that would explain how you gain more control with less mass.

if you want your particles to be controllable, setting exceptionally low conserve helps alot too. then your particles basically follow your fields exactly.


Thanks for the tip!
I changed the conserve to a low value but it seems that the goal would not have effect on the particles.
 
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