[Sidefx-houdini-list] Auto-resize voxel sim

François Duchesneau sidefx at trinix.ca
Thu Mar 24 14:57:21 EDT 2011


All makes sense guys. I'll implement it this way and yes it's faster 
with scattered points instead of  "Convert Volume Sop", I tested it.

Thanks

François

Michael Dunkley wrote:
> Bills message just reminded me of something for dealing with the fast fluids
> issue - I've seen an implementation where the scattered points are first
> advected by the velocity field using a vop in the sop solver, then mixed in
> with the unadvected points before piping into the bbox.  We haven't set it
> up here yet but certainly seems worth it.  And fwiw I'd definitely second
> the clip limits/geo option - unbounded sims can go all sorts of places you
> just don't care about.
>
> mike
>
> On Thu, Mar 24, 2011 at 2:05 PM, Bill Watral <bwatral at pixar.com> wrote:
>
>   
>> Hi,
>>
>> We put together something based on the scatter approach as an OTL. It has
>> been working well for us so far. Our approach is a bit more complicated then
>> just taking the field you want resize with (ie density or temperature)
>> because we ran into trouble with fast moving sources.
>>
>> The quick outline is:
>>
>> otl with a sop solver feeding into a gas resize field.
>>    within the sop solver:
>>
>>        1)Dop import pulling the field you want to use as the resize field,
>>        scatter into that dop import.
>>
>>        2)object merge your source (emitter) sop,
>>        scatter into this source.
>>
>>        3)Merge these two and bound the result.
>>
>>        4)Padding on the final output bound is used to adjust for velocity
>> of fluid to prevent clipping
>>
>>        5)We also added in a clip limit feature to limit the size of the
>> result based on a sop input.
>>
>>
>> The rough idea for this method came from conversations with sidefx.
>> I agree with Michael that the scatter might be a bit lighter.
>>
>>
>>
>>
>>
>>
>> On 03/24/2011 10:26 AM, Michael Dunkley wrote:
>>
>>     
>>> Hi François,
>>>
>>> http://www.cmivfx.com/tutorials/view/276/Houdini+Smoke+And+Dust
>>>
>>> There is a comparable method discussed in this video that uses a scatter
>>> ->
>>> bbox within a sop solver.
>>> Sounds very similar to what you're talking about, but the scatter might
>>> save
>>> you a few cycles over a volume conversion.
>>>
>>> best,
>>> mike
>>>
>>> 2011/3/24 François Duchesneau<sidefx at trinix.ca>
>>>
>>>
>>>
>>>       
>>>> Hi,
>>>>
>>>> I've figured out I can have an auto-resize based on the density field by
>>>> bringing it in sop and convert it to iso with a "Convert Volume Sop".
>>>> Than I
>>>> use that geo on a "Gas Resize Fluid" to do the automatic resize based on
>>>> its
>>>> bounding box.
>>>>
>>>> I'm going to create a hda for that but I'm wondering if I'm missing
>>>> something and reinventing the wheel. Is it already possible to it
>>>> directly
>>>> with "Gas Resize Fluid" or an other node inside dop?
>>>>
>>>> François
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>>>>
>>>>
>>>>
>>>>         
>>> _______________________________________________
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>>>
>>>       
>> --
>> Bill Watral
>> FX | TD
>> x4720
>>
>>
>>     
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