Wind Gust

[jake]

Hi,

I tried searching the forums, but I'm having trouble figuring out exactly what it is I want so I came up empty handed.

If this topic has been covered, please point me in the right direction.

I'm starting with a polygonal sphere. Starting at the top most point, particles start shooting out with a life of .5 seconds at an impulse rate of 300.

I set up an expression based on point color that as the frame range increases, more and more points will 'activate' and start spewing off particles.

Now I have a force on it that makes it look like the particle stream is gently blowing in the breeze.

However, I'm trying to figure out a way to make so that when the particle stream first activates, it has a much harder breeze on it, that lessons the longer the stream has been active, but I'm not sure how to create a source group for this effect. Kind of like a WOOSH! effect.

Since the particles have a short life an are constantly recreated, is there a way to go back and grab the original group from the SOP level and import it into the POP network?

Or is there another way to do this that I'm missing?

Thanks for any help.

[jake]

what if i were to set up some sort of geometry growth, so instead of particle streams, some geometry scales out. then i guess i'd have to use some sort of wire deformer on it to get the same kind of look i'm getting with the particles blowing gently in the breeze.

i'm really far from a houdini expert, so would this be a job better suited for pscale?

[GallenWolf]

Hiya Jake! Welcome to the forums. Hmm, perhaps if you posted your initial setup, we'd be able to help. I'm not sure exactly what you need.

However, I'm trying to figure out a way to make so that when the particle stream first activates, it has a much harder breeze on it, that lessons the longer the stream has been active, but I'm not sure how to create a source group for this effect. Kind of like a WOOSH! effect.

You may want to play with Drag POP as well as altering the mass. Keyframe the drag scale or mass perhaps that will get the effect you want.

GW

[old school]

I'm with GW. Work with the drag. Something like:

fit01( smooth($AGE, 0, 0.2), 0.1, 1 )

where smooth returns a nice ease curve from 0 to 1 as the age of the particle in seconds goes from in this example from 0 (start) to 0.2 seconds.

The result of the smooth() which goes from 0 to 1 is passed in to the fit01() expression which takes a value from 0 to 1 and maps it to in this case from 0.1 to 1.

You can use the same expression with different values to control the forces and the mass as well. The fit01() can also map incoming values in the opposite direction.

e.g.: fit01(smooth($AGE, 0, 0.2), 10, 0.5)

-jeff

[rob]

That works great , I presume you could also base Drag on a random ID also.

Rob

Edited October 1, 2008 by rob