different Birth Rates over time

[JDenker]

Hey Guys,

i have a little question. As the topic says i want to have different birth rates over time. i could easily do it with a spare channel and channel reference it the birth tab which i did at the end... but before that i thought of an expressions and it drove me crazy that i couldnt figure it out.

so basicly what i want is, from frame 1 to 30 i want to birth 300 particles, from frame 31 to 120 i want to birth 1000 particles and from frame 121 to 300 i want to birth 0 particles.

i came up with this but i won't work. i would love to see your suggestions.

if($F>=30&&$F<=120,1000,if($F<=30&&if($F>=0,200),0))

Thanks

-J

[rdg]

Hey Guys,

i have a little question. As the topic says i want to have different birth rates over time. i could easily do it with a spare channel and channel reference it the birth tab which i did at the end... but before that i thought of an expressions and it drove me crazy that i couldnt figure it out.

so basicly what i want is, from frame 1 to 30 i want to birth 300 particles, from frame 31 to 120 i want to birth 1000 particles and from frame 121 to 300 i want to birth 0 particles.

i came up with this but i won't work. i would love to see your suggestions.

if($F>=30&&$F<=120,1000,if($F<=30&&if($F>=0,200),0))

Thanks

-J

Maybe just put down some keyframes?

My first idea was to use chf() and a spare channel, but really: why not just keyframe it?

Another way would be to birth 1000 particles all the time and to animate the birth-probability, which would save you from unexpected bursts of particles.

Georg

[grasshopper]

Well you could always use this

1000 * fit($F,30,31,0.3,1) * fit($F,120,121,1,0)

[rdg]

Well you could always use this

1000 * fit($F,30,31,0.3,1) * fit($F,120,121,1,0)

Expression or die!

[mentor]

Go to "Aliases and variables" and choose Expressions tab, type something like this:

float b1(float fn)

{

float c = 0;

if (fn<50) c = 10;

else

if (fn>=50) c = 30;

return c;

}

Press "Aplly changes" and in "birth rate" field type b1($F) - thats all

Edited April 10, 2008 by mentor