particle over time

[alpotnis]

hi...i want my particles from the emitter to be affected by gravity only once they cross a certain particle age? any clue on how to achieve this?

[eetu]

Dunno if this is the best way, I put in an Attribute POP that writes a negative y value if $AGE > n

eetu.

pop_age_gravity.hip

[old school]

Add a Group POP above the Force POP. Give the group a real name. Enable the Rule option folder (toggle) in the Group POP and for the expression put:

$AGE > 1

which will put the the particles in this group whose age is greater than 1 second as age is in seconds.

or

You can put the expression

if($AGE > 1, -10, 0)

in the Force POP's Y parameter.

or

You can put the expression

if($AGE > 1, 1, 0)

in the Force POP's Scale parameter and set the Y Parameter to the desired force.

or

Use attributes as eetu did but I like to do the simple things simply. Every attribute added to POPs chews up more memory and allocating memory = slower.

----

Many ways to do this but the first three are the most common way to do this.

Use the expressions directly in the Force POP if this is the only place you are using the Age condition. You can also use $AGE after the POP simulation on subsequent SOPs.

Use the Group approach if you are using the condition in more than one subsequent POP. Groups created in POPs carry on to subsequent SOPs for further processing outside of the simulation.

Use the Attribute approach if you require much more control in further expressions to rework the condition or you have varying conditions per particle or you wish to visualize your condition explicitly in the viewport or later on process this attribute in SOPs.

A handy guide as to when to use your own custom attributes is to see how and when you use the default attributes like $AGE. "Do I want to have the same level of control as accessing the $AGE attribute?"

Edited September 14, 2009 by old school

[alpotnis]

thanks guys .. sorted !!