Particles moving within a sphere.

[Miles]

My sphere is moving from A to B. I only want it to emit a random number of points within the surfaces. But instead of standing still in the air when its moving, how can i make them stay inside the sphere. And not go outside it, only so they are moving with velocity inside of it.

Thanks in advance.

[stevenong]

Hi,

Do you need the particles to collide with the sphere etc? Or do you just want points scattered in a sphere?

If you want points scattered in a volume, you can append a IsoOffset SOP, set Output Type to Fog Volume, Mode to Implicit Sphere and finally append a Scatter SOP which will... erm... scatter points based on the density.

If you need them as particles, you can compute the velocity of the moving sphere using a Trail SOP and attribute transfer the velocity attribute (v) to the scattered points. In POPs, the scattered points will be your source and they should move within the sphere.

I've attached an example file.

Cheers!

steven

pts_in_sphere.zip

[Miles]

Thanks Steve, this is exactly what i wanted. But for instance, how would i add random velocity, to them going all around inside the sphere. So its not so uniform. Like having a sphere emitting particles, and setting the variance on the velocity, in the pop networks source ? Thanks in advance

Edited November 12, 2008 by Miles

[stevenong]

Hi Miles,

Put down a Point SOP, go to the Particle tab, turn on the Velocity parameter & use a noise() expression to randomize the values.

Cheers!

steven

[Miles]

Thank you very much, your knowledge is very much apriciated!