[Sidefx-houdini-list] nonLinear fluid reTime

Nick Zutphen nvanzutphen at live.com
Fri Jul 8 06:54:52 EDT 2011












On Jul 8, 2011, at 12:15 PM, sidefx-houdini-list-request at sidefx.com wrote:

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> Today's Topics:
> 
>   1. Re: Fix copy stamp N and up rotations (Dan Wills)
>   2. Re: Fix copy stamp N and up rotations (Pablo Gim?nez Pizarro)
>   3. nonLinear fluid reTime (Ben Frost)
>   4. Re: nonLinear fluid reTime (Szymon Kapeniak)
>   5. Re: nonLinear fluid reTime (Olex P)
>   6. Re: nonLinear fluid reTime (Szymon Kapeniak)
>   7. Re: nonLinear fluid reTime (Olex P)
> 
> 
> ----------------------------------------------------------------------
> 
> Message: 1
> Date: Fri, 8 Jul 2011 09:20:57 +0930
> From: Dan Wills <gdanzo at gmail.com>
> Subject: Re: [Sidefx-houdini-list] Fix copy stamp N and up rotations
> To: sidefx-houdini-list at sidefx.com
> Message-ID:
> 	<CAKnjVK3U-q-w_axx31xXS25BdGN+PDDUkW1omqaP6wns--485w at mail.gmail.com>
> Content-Type: text/plain; charset=ISO-8859-1
> 
> Hey Pablo, there's also a great reference for exactly what attributes do to
> copies/instances, here:
> 
> http://www.sidefx.com/index.php?option=com_forum&Itemid=172&page=viewtopic&t=6679
> 
> 2011/7/7 Pablo Gim?nez <pablogipi at gmail.com>
> 
>> Hi all.
>> When using copy stamp, if you provide a N and up attributes the operator
>> calculates the rotations using that coordiante system as a reference.
>> I am having some troubles with some geometry that at some point just jumps,
>> it orientation flickers. I have tought that probably the problem is that
>> the
>> copy operator is doing an euler rotation rather than using quaternions.
>> Not sure if somebody else have had the same problem before, but any advice
>> about waht is the best/easy way to get the same rotations but usign
>> quaternions would be gret.
>> Thanks!
>> 
>> --
>> Un saludo
>> Best Regards
>> Pablo Gim?nez
>> _______________________________________________
>> Sidefx-houdini-list mailing list
>> Sidefx-houdini-list at sidefx.com
>> https://lists.sidefx.com:443/mailman/listinfo/sidefx-houdini-list
>> 
> 
> 
> ------------------------------
> 
> Message: 2
> Date: Fri, 8 Jul 2011 09:36:55 +0200
> From: Pablo Gim?nez Pizarro <pablogipi at gmail.com>
> Subject: Re: [Sidefx-houdini-list] Fix copy stamp N and up rotations
> To: "sidefx-houdini-list at sidefx.com" <sidefx-houdini-list at sidefx.com>
> Message-ID: <E31565E8-B7A3-4EB3-AA5B-8D63FC53D37A at gmail.com>
> Content-Type: text/plain;	charset=utf-8
> 
> Thanks a lot dan, great reference!
> Best documentation a i have ever seen about copy sop and instancing. 
> 
> Enviado desde mi iPhone
> 
> El 8 Jul 2011, a las 01:50, Dan Wills <gdanzo at gmail.com> escribi?:
> 
>> Hey Pablo, there's also a great reference for exactly what attributes do to
>> copies/instances, here:
>> 
>> http://www.sidefx.com/index.php?option=com_forum&Itemid=172&page=viewtopic&t=6679
>> 
>> 2011/7/7 Pablo Gim?nez <pablogipi at gmail.com>
>> 
>>> Hi all.
>>> When using copy stamp, if you provide a N and up attributes the operator
>>> calculates the rotations using that coordiante system as a reference.
>>> I am having some troubles with some geometry that at some point just jumps,
>>> it orientation flickers. I have tought that probably the problem is that
>>> the
>>> copy operator is doing an euler rotation rather than using quaternions.
>>> Not sure if somebody else have had the same problem before, but any advice
>>> about waht is the best/easy way to get the same rotations but usign
>>> quaternions would be gret.
>>> Thanks!
>>> 
>>> --
>>> Un saludo
>>> Best Regards
>>> Pablo Gim?nez
>>> _______________________________________________
>>> Sidefx-houdini-list mailing list
>>> Sidefx-houdini-list at sidefx.com
>>> https://lists.sidefx.com:443/mailman/listinfo/sidefx-houdini-list
>>> 
>> _______________________________________________
>> Sidefx-houdini-list mailing list
>> Sidefx-houdini-list at sidefx.com
>> https://lists.sidefx.com:443/mailman/listinfo/sidefx-houdini-list
> 
> 
> ------------------------------
> 
> Message: 3
> Date: Fri, 8 Jul 2011 10:11:03 +0100
> From: Ben Frost <benfrost3d at gmail.com>
> Subject: [Sidefx-houdini-list] nonLinear fluid reTime
> To: sidefx-houdini-list at sidefx.com
> Message-ID:
> 	<CA+jg9Yp2iUUbx39VwpPc-cKeZSFHSzm5uwosCH_kEyjEKKaJyA at mail.gmail.com>
> Content-Type: text/plain; charset=ISO-8859-1
> 
> hi all..
> 
> I'm looking for anyones opinion regarding a non-linear reTime of a fluid
> sim.. and possible approaches to take.. the reTime is quite severe.. going
> from 24fps to around 432fps.. so 18 times slower.. and is based on a
> particle sim..
> 
> at the moment I'm using a brute force method for having the subSteps at 18,
> writing out the subFrame for each step.. and then read it back in, and
> reTiming.. this works.. but as you can imagine the sim times goes through
> the roof a bit.. and change the sim some what.. although it's more accurate
> it does create the problem of previewing the simulation at 18 subSteps..
> ideally I'd like to simulate at as fewer subSteps as possible.. until i'm
> happy with the sim.. and then upRess and bake out subFrames/subSteps..
> 
> we've reTimed the particles using the velocities to interpolate and get us
> the subFrames needed.. not sure there is a way to interpret this to fluid
> though..
> 
> and to make things worse.. I've been shown an animatable "sim scale" option
> in maya.. which works all too well.. I noticed houdini has the same option
> of sim scale, but this is only able to be set at sim start.. just wondering
> if this is possible to be manipulated and animate..?
> 
> anyway I'd be great to hear your opinions or possible more efficient less
> brute force approach..
> 
> cheers
> 
> ben..
> 
> 
> ------------------------------
> 
> Message: 4
> Date: Fri, 8 Jul 2011 11:33:31 +0200
> From: Szymon Kapeniak <szymon.kapeniak at gmail.com>
> Subject: Re: [Sidefx-houdini-list] nonLinear fluid reTime
> To: sidefx-houdini-list at sidefx.com
> Message-ID:
> 	<CAHDL27xt0Pt=rNEWfvEn3U_83qMtx9YbxtG_CcmxhhBD2PTwuQ at mail.gmail.com>
> Content-Type: text/plain; charset=ISO-8859-1
> 
> Hey Ben,
> fluids are volumes (SDF), so they could be interpolated by Timeblend,
> Sequenceblend and Timeshift Sops, similarly to plain geometries. I've
> never tried it on fluids, but theoretically this should work the same
> as on smoke (unless interpolating SDF is more computational
> problematic, than density fields).
> 
> So I would try to increase a little su- stepping to provide good
> samples for extreme interpolation, and retime my SDFs (taken straight
> from DOPS, without meshing), after which meshing should be possible as
> usual.
> 
> 
> hth,
> skk.
> 
> 2011/7/8 Ben Frost <benfrost3d at gmail.com>:
>> hi all..
>> 
>> I'm looking for anyones opinion regarding a non-linear reTime of a fluid
>> sim.. and possible approaches to take.. the reTime is quite severe.. going
>> from 24fps to around 432fps.. so 18 times slower.. and is based on a
>> particle sim..
>> 
>> at the moment I'm using a brute force method for having the subSteps at 18,
>> writing out the subFrame for each step.. and then read it back in, and
>> reTiming.. this works.. but as you can imagine the sim times goes through
>> the roof a bit.. and change the sim some what.. although it's more accurate
>> it does create the problem of previewing the simulation at 18 subSteps..
>> ideally I'd like to simulate at as fewer subSteps as possible.. until i'm
>> happy with the sim.. and then upRess and bake out subFrames/subSteps..
>> 
>> we've reTimed the particles using the velocities to interpolate and get us
>> the subFrames needed.. not sure there is a way to interpret this to fluid
>> though..
>> 
>> and to make things worse.. I've been shown an animatable "sim scale" option
>> in maya.. which works all too well.. I noticed houdini has the same option
>> of sim scale, but this is only able to be set at sim start.. just wondering
>> if this is possible to be manipulated and animate..?
>> 
>> anyway I'd be great to hear your opinions or possible more efficient less
>> brute force approach..
>> 
>> cheers
>> 
>> ben..
>> _______________________________________________
>> Sidefx-houdini-list mailing list
>> Sidefx-houdini-list at sidefx.com
>> https://lists.sidefx.com:443/mailman/listinfo/sidefx-houdini-list
>> 
> 
> 
> 
> -- 
> skk.
> 
> 
> ------------------------------
> 
> Message: 5
> Date: Fri, 8 Jul 2011 10:55:43 +0100
> From: Olex P <hoknamahn at gmail.com>
> Subject: Re: [Sidefx-houdini-list] nonLinear fluid reTime
> To: sidefx-houdini-list at sidefx.com
> Message-ID:
> 	<CAM=-8n64W+Sb7wEzPFLhttyBcBNkBG_-wPWS8--RoWQUcoKsKQ at mail.gmail.com>
> Content-Type: text/plain; charset=ISO-8859-1
> 
> I don't think that blending of two volumes in substep makes any sense
> especially if a difference in state of the fluid in two frames is high
> enough. But we can jump from Eulerian coordinate system (grids with
> static voxels and quantities going through this grid) to Lagrangian
> (particles where every particle is a local coordinate system with some
> quantity, let's say density, on it).
> In other words we can advect particles using velocity field,
> interpolate particle positions in subframes and put density and other
> needed attributes back into a grid.
> 
> On Fri, Jul 8, 2011 at 10:33 AM, Szymon Kapeniak
> <szymon.kapeniak at gmail.com> wrote:
>> Hey Ben,
>> fluids are volumes (SDF), so they could be interpolated by Timeblend,
>> Sequenceblend and Timeshift Sops, similarly to plain geometries. I've
>> never tried it on fluids, but theoretically this should work the same
>> as on smoke (unless interpolating SDF is more computational
>> problematic, than density fields).
>> 
>> So I would try to increase a little su- stepping to provide good
>> samples for extreme interpolation, and retime my SDFs (taken straight
>> from DOPS, without meshing), after which meshing should be possible as
>> usual.
>> 
>> 
>> hth,
>> skk.
>> 
>> 2011/7/8 Ben Frost <benfrost3d at gmail.com>:
>>> hi all..
>>> 
>>> I'm looking for anyones opinion regarding a non-linear reTime of a fluid
>>> sim.. and possible approaches to take.. the reTime is quite severe.. going
>>> from 24fps to around 432fps.. so 18 times slower.. and is based on a
>>> particle sim..
>>> 
>>> at the moment I'm using a brute force method for having the subSteps at 18,
>>> writing out the subFrame for each step.. and then read it back in, and
>>> reTiming.. this works.. but as you can imagine the sim times goes through
>>> the roof a bit.. and change the sim some what.. although it's more accurate
>>> it does create the problem of previewing the simulation at 18 subSteps..
>>> ideally I'd like to simulate at as fewer subSteps as possible.. until i'm
>>> happy with the sim.. and then upRess and bake out subFrames/subSteps..
>>> 
>>> we've reTimed the particles using the velocities to interpolate and get us
>>> the subFrames needed.. not sure there is a way to interpret this to fluid
>>> though..
>>> 
>>> and to make things worse.. I've been shown an animatable "sim scale" option
>>> in maya.. which works all too well.. I noticed houdini has the same option
>>> of sim scale, but this is only able to be set at sim start.. just wondering
>>> if this is possible to be manipulated and animate..?
>>> 
>>> anyway I'd be great to hear your opinions or possible more efficient less
>>> brute force approach..
>>> 
>>> cheers
>>> 
>>> ben..
>>> _______________________________________________
>>> Sidefx-houdini-list mailing list
>>> Sidefx-houdini-list at sidefx.com
>>> https://lists.sidefx.com:443/mailman/listinfo/sidefx-houdini-list
>>> 
>> 
>> 
>> 
>> --
>> skk.
>> _______________________________________________
>> Sidefx-houdini-list mailing list
>> Sidefx-houdini-list at sidefx.com
>> https://lists.sidefx.com:443/mailman/listinfo/sidefx-houdini-list
>> 
> 
> 
> ------------------------------
> 
> Message: 6
> Date: Fri, 8 Jul 2011 12:06:15 +0200
> From: Szymon Kapeniak <szymon.kapeniak at gmail.com>
> Subject: Re: [Sidefx-houdini-list] nonLinear fluid reTime
> To: sidefx-houdini-list at sidefx.com
> Message-ID:
> 	<CAHDL27w5aCtNRzOJujP8xZfcD=hKC8q1P=bHHknJb+gLrnCP4Q at mail.gmail.com>
> Content-Type: text/plain; charset=ISO-8859-1
> 
> 2011/7/8 Olex P <hoknamahn at gmail.com>:
>> I don't think that blending of two volumes in substep makes any sense
>> especially if a difference in state of the fluid in two frames is high
>> enough.
> 
> Well, people are using this technique to retime their smoke sims,
> Olex. I understand why blending volumes works worse than particles,
> but still it seems to be enough for most retiming cases, since frames
> tend to be similar.
> 
> Agree though, particles from volume might work better for high displacements.
> 
> But we can jump from Eulerian coordinate system (grids with
>> static voxels and quantities going through this grid) to Lagrangian
>> (particles where every particle is a local coordinate system with some
>> quantity, let's say density, on it).
>> In other words we can advect particles using velocity field,
>> interpolate particle positions in subframes and put density and other
>> needed attributes back into a grid.
>> 
>> On Fri, Jul 8, 2011 at 10:33 AM, Szymon Kapeniak
>> <szymon.kapeniak at gmail.com> wrote:
>>> Hey Ben,
>>> fluids are volumes (SDF), so they could be interpolated by Timeblend,
>>> Sequenceblend and Timeshift Sops, similarly to plain geometries. I've
>>> never tried it on fluids, but theoretically this should work the same
>>> as on smoke (unless interpolating SDF is more computational
>>> problematic, than density fields).
>>> 
>>> So I would try to increase a little su- stepping to provide good
>>> samples for extreme interpolation, and retime my SDFs (taken straight
>>> from DOPS, without meshing), after which meshing should be possible as
>>> usual.
>>> 
>>> 
>>> hth,
>>> skk.
>>> 
>>> 2011/7/8 Ben Frost <benfrost3d at gmail.com>:
>>>> hi all..
>>>> 
>>>> I'm looking for anyones opinion regarding a non-linear reTime of a fluid
>>>> sim.. and possible approaches to take.. the reTime is quite severe.. going
>>>> from 24fps to around 432fps.. so 18 times slower.. and is based on a
>>>> particle sim..
>>>> 
>>>> at the moment I'm using a brute force method for having the subSteps at 18,
>>>> writing out the subFrame for each step.. and then read it back in, and
>>>> reTiming.. this works.. but as you can imagine the sim times goes through
>>>> the roof a bit.. and change the sim some what.. although it's more accurate
>>>> it does create the problem of previewing the simulation at 18 subSteps..
>>>> ideally I'd like to simulate at as fewer subSteps as possible.. until i'm
>>>> happy with the sim.. and then upRess and bake out subFrames/subSteps..
>>>> 
>>>> we've reTimed the particles using the velocities to interpolate and get us
>>>> the subFrames needed.. not sure there is a way to interpret this to fluid
>>>> though..
>>>> 
>>>> and to make things worse.. I've been shown an animatable "sim scale" option
>>>> in maya.. which works all too well.. I noticed houdini has the same option
>>>> of sim scale, but this is only able to be set at sim start.. just wondering
>>>> if this is possible to be manipulated and animate..?
>>>> 
>>>> anyway I'd be great to hear your opinions or possible more efficient less
>>>> brute force approach..
>>>> 
>>>> cheers
>>>> 
>>>> ben..
>>>> _______________________________________________
>>>> Sidefx-houdini-list mailing list
>>>> Sidefx-houdini-list at sidefx.com
>>>> https://lists.sidefx.com:443/mailman/listinfo/sidefx-houdini-list
>>>> 
>>> 
>>> 
>>> 
>>> --
>>> skk.
>>> _______________________________________________
>>> Sidefx-houdini-list mailing list
>>> Sidefx-houdini-list at sidefx.com
>>> https://lists.sidefx.com:443/mailman/listinfo/sidefx-houdini-list
>>> 
>> _______________________________________________
>> Sidefx-houdini-list mailing list
>> Sidefx-houdini-list at sidefx.com
>> https://lists.sidefx.com:443/mailman/listinfo/sidefx-houdini-list
>> 
> 
> 
> 
> -- 
> skk.
> 
> 
> ------------------------------
> 
> Message: 7

I haven't tested this yet but how about animating the 'scale time' on the dop network? Shouldn't that take care of all that you need including 'just sim what you need'?

Cheers,
Nick van Zutphen

----
http://www.nickvanzutphen.com
> Date: Fri, 8 Jul 2011 11:15:13 +0100
> From: Olex P <hoknamahn at gmail.com>
> Subject: Re: [Sidefx-houdini-list] nonLinear fluid reTime
> To: sidefx-houdini-list at sidefx.com
> Message-ID:
> 	<CAM=-8n7D7L6kh3eczUQkKSr-VkC=3xO9tgzLXz1eJJrJCN8AuA at mail.gmail.com>
> Content-Type: text/plain; charset=ISO-8859-1
> 
> I agree in some situations it works (clouds in the sky?). While in
> others like let's say a plume of steam from a steam train (initial
> velocity is about 50-75 m/s) it wouldn't work.
> Plus particles have other benefits like additional details, rest positions etc.
> 
> On Fri, Jul 8, 2011 at 11:06 AM, Szymon Kapeniak
> <szymon.kapeniak at gmail.com> wrote:
>> 2011/7/8 Olex P <hoknamahn at gmail.com>:
>>> I don't think that blending of two volumes in substep makes any sense
>>> especially if a difference in state of the fluid in two frames is high
>>> enough.
>> 
>> Well, people are using this technique to retime their smoke sims,
>> Olex. I understand why blending volumes works worse than particles,
>> but still it seems to be enough for most retiming cases, since frames
>> tend to be similar.
>> 
>> Agree though, particles from volume might work better for high displacements.
>> 
>> ?But we can jump from Eulerian coordinate system (grids with
>>> static voxels and quantities going through this grid) to Lagrangian
>>> (particles where every particle is a local coordinate system with some
>>> quantity, let's say density, on it).
>>> In other words we can advect particles using velocity field,
>>> interpolate particle positions in subframes and put density and other
>>> needed attributes back into a grid.
>>> 
>>> On Fri, Jul 8, 2011 at 10:33 AM, Szymon Kapeniak
>>> <szymon.kapeniak at gmail.com> wrote:
>>>> Hey Ben,
>>>> fluids are volumes (SDF), so they could be interpolated by Timeblend,
>>>> Sequenceblend and Timeshift Sops, similarly to plain geometries. I've
>>>> never tried it on fluids, but theoretically this should work the same
>>>> as on smoke (unless interpolating SDF is more computational
>>>> problematic, than density fields).
>>>> 
>>>> So I would try to increase a little su- stepping to provide good
>>>> samples for extreme interpolation, and retime my SDFs (taken straight
>>>> from DOPS, without meshing), after which meshing should be possible as
>>>> usual.
>>>> 
>>>> 
>>>> hth,
>>>> skk.
>>>> 
>>>> 2011/7/8 Ben Frost <benfrost3d at gmail.com>:
>>>>> hi all..
>>>>> 
>>>>> I'm looking for anyones opinion regarding a non-linear reTime of a fluid
>>>>> sim.. and possible approaches to take.. the reTime is quite severe.. going
>>>>> from 24fps to around 432fps.. so 18 times slower.. and is based on a
>>>>> particle sim..
>>>>> 
>>>>> at the moment I'm using a brute force method for having the subSteps at 18,
>>>>> writing out the subFrame for each step.. and then read it back in, and
>>>>> reTiming.. this works.. but as you can imagine the sim times goes through
>>>>> the roof a bit.. and change the sim some what.. although it's more accurate
>>>>> it does create the problem of previewing the simulation at 18 subSteps..
>>>>> ideally I'd like to simulate at as fewer subSteps as possible.. until i'm
>>>>> happy with the sim.. and then upRess and bake out subFrames/subSteps..
>>>>> 
>>>>> we've reTimed the particles using the velocities to interpolate and get us
>>>>> the subFrames needed.. not sure there is a way to interpret this to fluid
>>>>> though..
>>>>> 
>>>>> and to make things worse.. I've been shown an animatable "sim scale" option
>>>>> in maya.. which works all too well.. I noticed houdini has the same option
>>>>> of sim scale, but this is only able to be set at sim start.. just wondering
>>>>> if this is possible to be manipulated and animate..?
>>>>> 
>>>>> anyway I'd be great to hear your opinions or possible more efficient less
>>>>> brute force approach..
>>>>> 
>>>>> cheers
>>>>> 
>>>>> ben..
>>>>> _______________________________________________
>>>>> Sidefx-houdini-list mailing list
>>>>> Sidefx-houdini-list at sidefx.com
>>>>> https://lists.sidefx.com:443/mailman/listinfo/sidefx-houdini-list
>>>>> 
>>>> 
>>>> 
>>>> 
>>>> --
>>>> skk.
>>>> _______________________________________________
>>>> Sidefx-houdini-list mailing list
>>>> Sidefx-houdini-list at sidefx.com
>>>> https://lists.sidefx.com:443/mailman/listinfo/sidefx-houdini-list
>>>> 
>>> _______________________________________________
>>> Sidefx-houdini-list mailing list
>>> Sidefx-houdini-list at sidefx.com
>>> https://lists.sidefx.com:443/mailman/listinfo/sidefx-houdini-list
>>> 
>> 
>> 
>> 
>> --
>> skk.
>> _______________________________________________
>> Sidefx-houdini-list mailing list
>> Sidefx-houdini-list at sidefx.com
>> https://lists.sidefx.com:443/mailman/listinfo/sidefx-houdini-list
>> 
> 
> 
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> 
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