probability curves?

[super gnu]

im wondering if there is a way to "bias" simulation value ranges...  for example i have spray coming from a tyre.. i use an age test set to detatch particles from tyre after 6 frames, with a variation of 6 frames.    this spreads the spray out nicely... however i wish the majority of the spray to detatch earlier, with progressively less droplets flying off  as we get further up the back of the tyre. 

ideally id have a button with a small bezier graph, for each value which has a "variation" spinner.. that way i could draw a  curve to define distribution. 

is there a (do-able for a non-mathematician like me) way to achieve this now? 

i was considering dividing particles up into lots of events and treating them separately but this seems very hacky and over complex.

[d4rk3lf]

If I understand correctly...
Maybe animate "per frame" parameter in the birth, or spawn operator?

[super gnu]

thats not quite what im after.

an example.. (probably achievable in other ways but still)

i have particles with a radius assigned, and use the "variation" spinner to get different sizes. using those two controls however i can only get an even distribution of sizes within that range..

if i had another button which opened a range graph, i could draw a curve starting flat, with a sharp dip at the end.. this would mean the majority of particles would be smaller, with many less of the larger sizes.. the larger, the less probable. this is a simple example, the curve could have more than one peak.

this can be applied to velocities, scales, particle counts, forces etc etc..

basically if you have ever used forestpack, it uses this system, and its very powerful.

[yossarian678]

I'm following up on this to see if anybody has any good solutions. This would be especially useful for scale randomization as a lot of times the look I'm going for is random scale but much fewer larger bits than smaller bits. In Houdini I'd do a random between 1and 0 to get an even distribution of values then multiply that by a curve that stays very low until it gets to the last 15% or so at which point it shoots up to finish at 1 on the right side.