[Sidefx-houdini-list] POP's: best way to threshold particle emission based on an point attribute

Peter Bowmar pbowmar at gmail.com
Mon Nov 15 18:55:39 EST 2010

Hi Miles,

No Houdini here right now but if your attribute has local variables,
you can use the Birth Probability field, for example if you copy your
attribute into (for example) Cd, make sure Cd is being inherited, then


in both, where $CR is black you get none, where it is 1 you get full birthing.

At least, that's how I vaguely remember doing it ;)

Peter B

On 15 November 2010 15:41, Miles Green <Miles.Green at al.com.au> wrote:
> Hi,
>  does anyone have any recommendation's for the best/fastest/most
> efficient way to birth particles from polygons based on a custom point
> attribute?
> the two methods I currently have are;
> 1)  inherit the custom attribute into pops via the source node, then
> follow it with a  kill Node that checks if the custom attribute is under
> a certain threshold
>  - NOTE: this seems wasteful to me as the particles are created and
> then killed
> 2) use a scatter  in sops before the popnetwork to create birth points
> on the poly, and then use a delete Node to delete those points where the
> custom attribute is under a certain threshold
>  - NOTE: this seems slower than solution (1)  above
> I ideally would like to use the custom attribute directly in the popnets
> source node to specify that particles never get created if the custom
> attribute is below a certain value
> thanks for any help
>  Miles
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