selecting a random bunch of particles per frame

[dagoose]

Hi,

It's driving me nuts ... sounds so simple but just can't get it to work.

Lets say I have an box which are emitted particles into. Now I define a pop group via a bounding and want to delete 25 particles every frame in the bounding.

Thanks for yout help.

delete_rand_particles_per_frame.hip

[Atom]

Try using a PopKill instead of a PopWrangle. You can specify the group and use the Random tab to randomly remove some particle in the group.

 

[dimovfx]

or if you still want to use wrangle, try with something like

float seed = @id + @Frame;
if (rand(seed) < 0.025) @dead = 1;

 

Edited January 24, 2017 by sasho78

[dagoose]

Quote

 

Thanks you guys!

I am guessing that the rand function is supposed to return an equal spread ... still it is very hard to control the amount of particles getting deleted.

 

[eetu]

In cases when you need to randomly delete strictly a given number of elements, one way is to sort the elements randomly and then delete N first ones.

If you need to maintain the point order, you could probably sort a separate copy of the particles, select first N to a group and match that back to the originals according to id.

Or script it.