# power of gas repeat solver

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Very very coolest gas micrisolver appeared in h12. It is gas repeat solver. For example, with it you can implement the logic conditions div(vel) =0 , realized in gas project non divergent DOP and other loop based logics.

gas project sim.hipnc

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the little example to use gas repeat for a dynamic retime pyro simulations.

dinamic retime explosion.mov

expl_gas_repeat2.hipnc

Edited by chumbuk
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this is really awesome, and I was wondering how to achieve a retiming effect... thanks for the hip!!!

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the little example to use gas repeat for a dynamic retime pyro simulations.

Hi thanks for the hip - really helpful -

can you explain what the feedback wave subnet is doing in the sim?

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can you explain what the feedback wave subnet is doing in the sim?

This is a optional component of the return motion of the gas, after the separation shock wave. But this is not the essence of the example. The main thing is possibility gas repeat solver in this context.

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This is a optional component of the return motion of the gas, after the separation shock wave. But this is not the essence of the example. The main thing is possibility gas repeat solver in this context.

yes of course - was just wondering what they were doing exactly - i couldn't see any difference with or without - but really curious what it does ?

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Interesting!

Have you tried to do something that breaks out of the while loop according to a condition?

Regarding your second example, if I understand it correctly, couldn't you achieve the same effect by just keyframing the timestep magnitude as well as number of substeps?

That way you could retime more smoothly, but by repeating passes you're essentially retiming by integer multiples.

Cool stuff, and inspiring to see nondivergence done by hand

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yes of course - was just wondering what they were doing exactly - i couldn't see any difference with or without - but really curious what it does ?

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Look at the comparison between the two versions with and without, 7-12 frame in attach.

This is a brief sketch of the return movement of a short-term downward pressure as a result of the separation shock wave.

low pressure.mov

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Have you tried to do something that breaks out of the while loop according to a condition?

There have not tried it, what do you mean?

Regarding your second example, if I understand it correctly, couldn't you achieve the same effect by just keyframing the timestep magnitude as well as number of substeps?

That way you could retime more smoothly, but by repeating passes you're essentially retiming by integer multiples.

Yes it's integer retiming. You can get a similar effect in other ways. But I do not know method that as simple as a way with gas repeat.

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hey I am quite new to customizing all my Dops in such a way... so I was wondering over a few things...

First and for all... how do you keep the nice looking shape in your fire with the repeat solver in the network?

when ever I want to use it all i get is a big ball and thats it. but you still got swirl and everything in the shape and no matter what I do i never get something that looks even close to ok.

And my second question would be, how to you break geo with fluid effects?

I went over your scene file a hundred times and I thought that I found out how(enabling the "collision from velocity field" function in the pyro object)

but its never breaking the geo....

got any tips for me... I am really lost:)

thanks

Juri

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hey I am quite new to customizing all my Dops in such a way... so I was wondering over a few things...

First and for all... how do you keep the nice looking shape in your fire with the repeat solver in the network?

when ever I want to use it all i get is a big ball and thats it. but you still got swirl and everything in the shape and no matter what I do i never get something that looks even close to ok.

And my second question would be, how to you break geo with fluid effects?

I went over your scene file a hundred times and I thought that I found out how(enabling the "collision from velocity field" function in the pyro object)

but its never breaking the geo....

got any tips for me... I am really lost:)

thanks

Juri

You can see setting a pyro solver in the project, the dynamics of fire depends on many parameters, the cooling rate, fuel parameters, temperature, etc.

This project is made for fast, to show how to use the gas repeat solver, for the non standart way. Namely, that with it you can retime the action of a large system such as pyro solver.

RBD has been pushed by to use "feedback scale" parameters in pyro solver. This is not the best way, but it is easiest to make an example.

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This looks quite interesting, however I don't know what I am doing wrong. The Gas Repeat Solver (well, all microsolvers) got changed, so you can't plug it in like in the example hip above (expl_gas_repeat2.hipnc). I've tried plugging it in directly to one of the Pyro Solvers inputs, attach it to a MultiSolver after the Pyro Solver - even tried to plug it in inside the Pyro Solver. But it doesn't seem to do anything at all, wherever I plug it in there isn't any difference to the sim.

I tried installing H12.1 and had a look at the hip, and yeah it works exactly as expected there. Anyone have a clue how to do it in 12.5?

Edited by Skybar

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Great info...really thanx

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This looks quite interesting, however I don't know what I am doing wrong. The Gas Repeat Solver (well, all microsolvers) got changed, so you can't plug it in like in the example hip above (expl_gas_repeat2.hipnc). I've tried plugging it in directly to one of the Pyro Solvers inputs, attach it to a MultiSolver after the Pyro Solver - even tried to plug it in inside the Pyro Solver. But it doesn't seem to do anything at all, wherever I plug it in there isn't any difference to the sim.

I tried installing H12.1 and had a look at the hip, and yeah it works exactly as expected there. Anyone have a clue how to do it in 12.5?

Hmm actually it does seem to work if I pipe it into the last Multi Solver in PyroSolver/SmokeSolver, and piping the three connections already there into the Gas Repeat instead. Bit of a longer route, but it does work

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Hmm actually it does seem to work if I pipe it into the last Multi Solver in PyroSolver/SmokeSolver, and piping the three connections already there into the Gas Repeat instead. Bit of a longer route, but it does work

Hi, Skybar!

Have you get a nice way to solver the problem on H12.5, it seems any change in gas repeat solver sop from H12.1.

But i can not understand the idea you mentioned,forgive my poor understanding.

Can you make a simple sketch, or a simple hip will be best.

Thanks.

Edited by wateryfield

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Hi, Skybar!

Have you get a nice way to solver the problem on H12.5, it seems any change in gas repeat solver sop from H12.1.

But i can not understand the idea you mentioned,forgive my poor understanding.

Can you make a simple sketch, or a simple hip will be best.

Thanks.

Hey, sure, here you go

gasrepeat12.5.hipnc

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Hey, sure, here you go

gasrepeat12.5.hipnc

Thanks! Skybar.

I get it.

Actually you surprised me, how can you find that method.

It seems i have to learn so much.

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Thanks! Skybar.

I get it.

Actually you surprised me, how can you find that method.

It seems i have to learn so much.

It's all about trying stuff out and eventually you'll understand how things work. 7 months ago I knew nothing about Houdini, just take tiny steps and don't get overwhelmed, theres no need to rush

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Can someone briefly explain what I would want to use the Gas Repeat Solver for? I suppose there are a few different reasons.

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retime animations (speed up, slow down), generate preroll without saving anything.

-G

Can someone briefly explain what I would want to use the Gas Repeat Solver for? I suppose there are a few different reasons.