[Sidefx-houdini-list] particle fluid kill plane

Jason Johnston jasonj at pixar.com
Fri Aug 12 13:56:58 EDT 2016


I believe all you need to do is put down a pop kill dop and put in this 
code:

if (v at P.y < -4) removepoint(geoself(), @ptnum);


-Jason

On 08/12/2016 10:50 AM, François Duchesneau wrote:
> I think he's talking about killing particles during the sim inside 
> Dop. This would work only when using a Sop Solver within the simulation.
>
> That brings a question. I think at some point there was an overhead 
> when using sop nodes on a simulation through a Sop Solver because the 
> geometry had to be copied again or something like that. Anyone knows 
> if it's still the case? In order words, is using a sop solver on the 
> points of a heavy particle sim slows down the computation apart from 
> the nodes used inside the sop solver of course?
>
> Thanks
>
> François
>
> On 08/12/2016 01:44 PM, Neil Dickson wrote:
>> The Clip SOP also works on points, so you can just use that if you 
>> don't want to fuss around with VEX or expressions. You can just set 
>> the direction and position with the viewport handles or the parameter 
>> pane if you want them to be exact.
>>
>> Cheers,
>> Neil
>>
>> On 12/08/2016 1:14 PM, Mark Elendt wrote:
>>> If you have the plane normal, (A, B, C), you can define an equation
>>> for the plane:
>>>      A*x + B*y + C*z + D
>>> where D moves the plane up and down along the normal (from the
>>> origin).
>>>
>>> If you take a point (x,y,z) and plug it into the equation, positive
>>> values mean the point is above the plane, negative values below.
>>>
>>> So, in VEX:
>>>
>>>      cvex
>>>      partitionplane(vector N; float D)
>>>      {
>>>     float dist = dot(@P, normalize(N)) + D;
>>>
>>>     if (dist > 0)
>>>         addgroup("dist", @ptnum);
>>>     else if (dist == 0)
>>>         addgroup("onplane", @ptnum);
>>>     else
>>>         addgroup("below", @ptnum);
>>>      }
>>>
>>>      On Friday Aug 12 at 10:03, Gary Jaeger wrote:
>>>> no that would work. A kill plane is just that. A plane that kills 
>>>> the particles. It can be at any arbitrary angle but generally I use 
>>>> them to kill particles in the Y.
>>>>
>>>> I’ll see if I can figure that out :)
>>>>
>>>> Gary Jaeger / 650.728.7957 direct / 415.518.1419 mobile
>>>> http://corestudio.com <http://corestudio.com/>
>>>>> On Aug 12, 2016, at 9:53 AM, François Duchesneau 
>>>>> <sidefx at trinix.ca> wrote:
>>>>>
>>>>> I've never used Bifrost. What is the kill plane?
>>>>>
>>>>> If you're referring to a way of kill particles below a certain 
>>>>> value in Y for example you could use an expression in the Kill Pop 
>>>>> but I suspect what you're after is more sophisticated.
>>>>>
>>>>> Francois
>>>>>
>>>>> On 08/12/2016 12:35 PM, Gary Jaeger wrote:
>>>>>> Noob question. Is there an equivalent to the bifrost kill plane 
>>>>>> for particle fluids?
>>>>>>
>>>>>> Gary Jaeger / 650.728.7957 direct / 415.518.1419 mobile
>>>>>> http://corestudio.com <http://corestudio.com/>
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