Particle Questions

[pixl]

Particle Questions:
I'm using particles to create and effect if an image being sprayed out of a projector.
I've created a grid of particles w/the desired texture assigned, and I've tried various combos of forces and collision objects to get the motion.

My questions are:
1) Is there a way to control when the particles start moving (ie are affected by the forces)?
2) Is there a way to add a bit of randomness to the particle motion?

Thanks much.

[joojaa]

QUOTE(PixL @ 08/27/08, 02:43 AM) [snapback]290480[/snapback]
1) Is there a way to control when the particles start moving (ie are affected by the forces)?

yes, you can put mass sky high. or you can just make a post dynamic expression that puts them back to pos0 And 0 velocity-
QUOTE
2) Is there a way to add a bit of randomness to the particle motion?

Yes, use mass a noise field or whatever. (but dont use a gravity fiesld for mass objects)

[pixl]

Thanks Jooja:
I'm starting w/a grid of particles which has been saved as an "initial state", so if when I change the mass, it is the same for all of them.

When you mention a noise field, are you referring to turbulence? And why avoid using gravity?
Thanks again.

[joojaa]

QUOTE(PixL @ 08/27/08, 10:48 AM) [snapback]290506[/snapback]
Thanks Jooja:
I'm starting w/a grid of particles which has been saved as an "initial state", so if when I change the mass, it is the same for all of them.

Ahh theres 2 mass attributes one for the netire particle and one per particle one, thet sin the expresion section. You can set them either with a startup script, runtims script or the component editor.

[pixl]

Hmm.
I tried this:
RMB on the "Mass" field in the Per Particle Attributes and created a "Before Dynamics" expression of:
rand(.5,10);
but no effect.

I also tried this:
RMB on the "Mass" field in the Per Particle Attributes, choose the Component Editor and paste the same expression into the hilited field, which is "Particle Shape" in the "Weighted Deformer" tab, but the expression is removed when I hit Enter.

Do you know what I'm doing wrong?
Thanks.

[joojaa]

QUOTE(PixL @ 08/28/08, 03:24 AM) [snapback]290566[/snapback]
Hmm.
I tried this:
RMB on the "Mass" field in the Per Particle Attributes and created a "Before Dynamics" expression of:
rand(.5,10);

try putting it in creation, the rand evens out on long run otherwise. The range is dependent on the force strangth. A big number is one thats hundreds f times the tregth of the field.

QUOTE(PixL @ 08/28/08, 03:24 AM) [snapback]290566[/snapback]
Do you know what I'm doing wrong?

Mass does not affect gravity fields (gravity, newtonian), because by definition gravity acts the same irrespetively the mass. Newtonian gets a new meaning when you use a mass distribution With pwr particle applied.

[pixl]

QUOTE(Joojaa @ 08/28/08, 12:24 AM) [snapback]290576[/snapback]
Mass does not affect gravity fields (gravity, newtonian), because by definition gravity acts the same irrespetively the mass. Newtonian gets a new meaning when you use a mass distribution With pwr particle applied.

That's good to know.
I'm not using either of those - I'm using radial, turbulence, drag, and collisions.
As for adding the expression, it doesn't seem to be staying in the expression editor. When I open the expression editor and select the particle object, I'm not able to create a new expression (the button is grayed out). When I select an attribute of the particle and set a rand() expression, it doesn't stay in the expression when I click a different attribute and then click back. No doubt a sign of dabbling in a new area...

I've got kind of a cool effect happening, but it looks a bit like fabric since I'm starting w/a grid of particles. What I wanted to accomplish by varying the dynamic weights was to get more a "particle" feeling, but I can live without it.

One other question. Now I have a grid of particles (a single particle object) connected to various forces and collision objects. The resistance settings for the collision objects are connected to the particle. If I generate a similar particle in a different scene (say with a different texture), is there a way to replace the particle in the current scene, which has all the dynamic connections, with a particle from a different scene?
Thanks as always.

[pixl]

Problem solved:
For the Per Particle Mass, in the AE, I added the expression:
particleShape1.mass = rand(0.15,6);
to run before dynamics and I got what I was after.
Take care.