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Smoke Dissipation, Fire Burn rate, Turbulence

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  • Smoke Dissipation, Fire Burn rate, Turbulence

    I was wondering if these suggestions might be of any interest to you guys, especially for fire simulations.

    I noticed in our present project, when we were doing a slow motion explosion simulation, a couple of things which might throw some light on Phoenix's features.

    1.We found it a bit hard to control the burning of fire.. lets say, we wanted to keep the burning of the fire for a longer time. A control like
    burn rate, where we could say.. Fire can burn longer or burn for shorter time, would have been really helpful.

    2. The conservation methods are great, but they inherently change the over all turbulence in the fire, which is fine. But once the conservation is changed, there is hardly any control for the over turbulence. I am not sure if i made sense on this, but I found Multi pass conservation great for fire, but then i couldnt control the size of turbulence inside it. even after changing the methods from buffered to smooth to PCG symmetric. Is it possible to give user a bit of control interms of adding turbulence. I know there is PHX_turbulence node, but as such before adding that, there is inbuilt turbulence inside the fire, any parameter to tweak this would be pretty helpful.

    3. Regarding smoke, the dissipation of smoke is great, then again, a parameter to specify when the smoke could dissipate, like giving a threshold value and smoke could start to dissipate, if the smoke goes less or more than that value could be very helpful.

    4. Maya fluids have diffusion, where the density of the grid flows into adjacent voxels. A parameter like this, to soften out the smoke would be helpful.

    All in all, Phoenix is a phenomenal simulator, especially considering it can do both liquids and fire simulations with such an ease.

    If you guys have any work around for the issues i mentioned above, I would love to hear.

    Regards
    Kishore Guntuku, Cine-Chromatix KG. Berlin

  • #2
    Thanks a ton for these! 3 is a very good point and goes into the TODO list, 4 is already there.

    Regarding the prolonged burning, not long ago in the nightlies we added a 'fuel depletion' parameter, which sounds like what you need - you can reduce it and the fire would burn longer.

    Regarding conservation and advection - conservation for smoke/fire generally controls how much the fluid rolls, how well it keeps its volume and momentum and thus how far a shockwave can travel. Basically PCG is good for rolling, Direct Symm is good for shockwaves, buffered produces small curls and swirls and smooth is.. smooth and keeps the fluid tight. The more Quality you put in conservation, the stronger rolling and shockwave effect there would be.

    Advections on the other hand control how well the fluid moves through the grid - Multipass is an improved version of Classic with more detail but potentially less symmetry, and Forward Transfer is an alternative to Classic which keeps the volume of the fluid from disappearing. You'd also want to increase the Steps per Frame if you have fast movement of fluid inside the simulator, otherwise the fluid will tear up and grain out. The more steps you use though, the more diffusion you will get and you will lose details.

    So if you need a specific turbulence frequency, I'd really suggest the turbulence helper - any additional turbulence will be a natural effect of the conservation method you use, but it won't be controllable.

    Hope this helps! Thanks again for the suggestions!
    Svetlin Nikolov, Ex Phoenix team lead

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    • #3
      Thanks a lot Svetlin for the reply. You guys at chaos group are really awesome. we can always count on you for the support.

      1. Thanks for pointing out the fuel depletion, I didnt notice it at all, may be because I didnt use fuel in the source. This could have helped. I will give try on it and see how it goes.

      2. Thanks for the detailed info on the advection and conservation methods. Then I will do trying combining the advection and conservation methods to get closer to what we are looking, hopefully.

      regading point 4, Is it available in the nightlies or will be in the new 3.0 version for Maya ?

      and many thanks for the reply and wishing you luck with new release.
      2.
      Kishore Guntuku, Cine-Chromatix KG. Berlin

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      • #4
        Ah, 4 is in the TODO list, yes - not yet in the builds though. I'll see if we can add this for 3.0 for Maya, but there are already a couple hundred points in the list there, so not really sure if we can go through all until then.

        If you find or need anything, please give us a bump - it might not be ready quickly, but still it would certainly be good to know about it - often we jump between areas of Phoenix where several requests have accumulated and do all of them at once, so it certainly helps us plan better if we know what is needed.

        Big thanks!
        Svetlin Nikolov, Ex Phoenix team lead

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        • #5
          I can completely understand that
          It would be great to see these requests added at some point though, no rush at the moment.
          Thanks again
          Kishore Guntuku, Cine-Chromatix KG. Berlin

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