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

Miles Green Miles.Green at al.com.au
Tue Nov 16 00:50:21 EST 2010


thanks for the info Guys, as always I love the feedback I get for my 
simple troubles

I have plenty to play with now..

 cheers M

François Duchesneau wrote:
> Me too I prefer to create my emitter in sop. The advantage is that you 
> can see your emitter points and normals (which are then used for initial 
> velocity in pop) as Rangi stated. Also, when you apply noise on  scatter 
> points, it is a lot more precise than a noise on a surface from which 
> the emission on surface will interpolate from.
>
> The disadvantage is the speed so I almost always bake raw points with 
> the number of substep I plan to use. I do that locally and even if it 
> takes me 3 minutes to bake, after that I usually don't need to do it 
> again since most of my changes are on the emission noise on density, 
> normal length and orientation and this doesn't have to be baked to be 
> fast since I do that in vop.
>
> François
>
> Miles Green 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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>>     
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-- 
Miles Green
Digital Artist, FX Lead TD, Guardians
T: +61 [0]2 938 32378




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