# Some Particle Questions

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Hi,

I'm currently writing a thesis about Particles and am saying a few words about any Particlesystem out there..

I never realy used Houdini, so I hope someone could help me by answering this questions:

1.) Let's say our Particles start at position 0, 0, 0. Is it possible to let them fly to a specific Point and, as soon as they arrive there to let them fly to an other Point? (i.E. Fly from start to Object A, then to Object .

Any particle should fly from start -> A -> B.

2.) Is it possible to make particles follow a curve?

If yes, what happens if the particles are very fast, or the curve has very tight angles? Do they fly off, of the curve?

3.) The same thing with the surface of an Object, can Particles fly along this surface?

4.) There are 6 Target Objects. Each particle should pick one Object (Random or Nearest) and fly to this one.

5.) If it's all possible.. can all 4 things happen consecutively? So when the reached Point B, they should fly along the path (the Path start's at point . At the end of the Path is the Object where they should fly along etc..

That's all..

Would be great if you could tell me if this is possible, and if so.. how it's possible to do (Don't need a Tutorial about this, just things like "This can be done by using the follow curve Node" or something)

Ah, and one thing: Anything without Expressions, only built in features

Thanks a lot!

Kind regards,

Ayani

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Hello,

1) Yes. You should be able to specify that once the particle reached the threshold of certain proximity to the first target, begin heading toward another target instead. If you're doing this using proximity approach, what will happen to that same particle when it's traveling further and further away from the first target? In particle system, this would probably make the particle wanting to go back to the first target as it thinks that it's still not within the threshold from the first target. So, you'll to figure out how to "trigger" an event once the threshold is reached and travel toward the secon target eventhough the it's getting further and further from the first.

2, 3) Yes, you can make particle travel along a curve. At least in Houdini... And yes, if your velocity is very high, it will shoot out and escape from curve. This is only true if you're using particle system that's being controlled by velocity and forces. Basically, when you have a very sharp turn corner, and your velocity is very high, your particle will escape from the 'grasp' of the curve. Basically like centrifugal forces. If you were to write your own particle system, I'd imagine that you'd probably have to figure out a way to have your particle read the closest point on the curve and find out the directional vector of that closest point. Once you have that info, adjust your velocity/forces accordingly or however you want to do with it. The same could apply for surface.

4) I don't see why not... At least from Houdini's point of view. It's just a matter of shuffling targets into group (either randomly or by proximity) and have your particle see only that targets internally.

5) I think you can... Depending on what you're trying to do on this one tho. Otherwise, you'll just have to take the sum of all your vectors (and perhaps interpolate them accordingly) to get your final direction and magnitude, yes?

Now, I am just thinking those out loud. I am sure there are many things I probably have neglected. So, I could be wrong about a lot of stuff.

Hope that helped, tho.

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