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

Michael Dunkley mdunkley at gmail.com
Thu Mar 24 14:35:21 EDT 2011


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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