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pop advection by fluid methods ?


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Hi Guys,

 

I would like to know what would be the fastest / best approach to advect pop on a pyro vel field.

I want that the advection happen in the same time as the pyro sim.

i find that using multisolver looks to be the cleanest approach but i'm not sure ?

 

i have assemble a simple scene that works smoothly but i get an error signal on my pyro nodes,

so i would like to get some expert pov to know what i am doing wrong !

 

Thanks for your time

 

Cheers

 

E

advection.hip

Edited by sebkaine
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Hi Paul !

 

Hope you're doing well dude ! :)

 

Thanks for your help ! The fact of having 2 dop is a cool method, but for this one i was trying to get all the DOP tree inside one DOP network instead of 2.

I find it more straightforward for playing with parameters.

 

that's why i find using multisolver could be a cool approach , i would be curious to know other trick to do this in order to do a pro/cons of each approach !

 

Thanks again for your help !

Edited by sebkaine
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Howdy,

 

Here's a slightly different multisolver setup that doesn't seem to be getting any errors.  Although I think yours are just warnings and they don't seem to mess up anything.

 

simplepyropopadvect.hip

 

And here's another example I was working on from a different post

 

 

http://forums.odforce.net/topic/22809-how-to-retain-advected-velocity-of-particles-as-new-particles-are-created/

 

It's a similar concept to what your working on and I think this file could have some cool uses.

 

particlestest_v03.hip

 

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thanks for your reply guys ! i'm gonna check this in depth !

 

very cool hip Richard ! thx for sharing ... :)

By the way i still have the same warnings on Pyro solver with your exemple ...

I don't know what is the origin of this ... and how to fix this ?

 

i will keep testing this to see what approach i like the most ...

Edited by sebkaine
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It depends on what you are after of course, but you could just tweak and sim the Pyro until you feel satisfied - cache that out - and then in a seperate POP Sim use "POP Advect by Volumes". This would allow you to tweak the particles seperately, adding additional forces and whatnot - without having to constantly re-sim the Pyro which you are already happy with.

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It depends on what you are after of course, but you could just tweak and sim the Pyro until you feel satisfied - cache that out - and then in a seperate POP Sim use "POP Advect by Volumes". This would allow you to tweak the particles seperately, adding additional forces and whatnot - without having to constantly re-sim the Pyro which you are already happy with.

 

I completely agree with this.  Get the pyro sim how you want it, save it to disk, do the particles in their own pass. It'll likely be a good bit faster not having to deal with the pyro sim at the same time as well.

 

In 13 I used to use the gas advect microsolver to advect points as it was more accurate to the pyro sim. The new pop advect by volumes in 14 now has more advection methods (such as the trace method, which is the same as pyro's default), and mimics the gas advect node. It's much better than before, and both are good options.  

 

I just opened the file -- if you look at Method 2, switch the advection type to trace. It might not look like a big difference, but doing a simple velocity sample and apply (single step advection) won't be accurate, especially if you have a strong emitter. However, the trace method will more or less 'trace' it's way through the field, moving voxel by voxel and resampling as it goes based on the 'cfl' -- it will result in a sim that matches the pyro much better. You may have to lower the cfl below 1 just a bit to make it work better I noticed a while back. The cfl kind of controls how big of a step it's allowed to take. The advect by volumes is vex, so it's fast too. I'm sure the gas advect is also multithreaded, but I haven't done any benchmarks. 

 

 Another awesome thing about houdini -- check out $HFS\houdini\vex\include\advect.h   if you want to see the code for how the new advect by volumes stuff works.  :D

Edited by Solitude
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Mmm, here's another way to advect points which is probably the fastest, tested it on a shot with around 20million points for 750 frames.

 

But, that's not in dops... although there may be a way of doing it in a sop solver

Well, the Solver SOP is just a neat package for a DopNet + Sop Solver. So you are already doing it with Dops sort of.

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