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  • Smoke Resimulation Questions

    Hi all, I'm attempting to resimulate a smoke sim (slowing down to 25% speed).

    When I stop the resimulation then resume it later by changing the Custom Start Frame to whatever the last cached frame was, the appearance is different, as if it's restarting at a different place in the resim. The help docs on the Input section indicate that for slow smoke simulations, the best approach is to use Precise Tracking, so I wonder if that's part of the problem. Unfortunately I only included Smoke, Velocity, and Wavelet, and don't have time to resim with Advection Origin included before my deadline.

    I've got a few resimulation questions based on this:

    1. Given that I didn't include Advection Origin, is it normal that my resimulation doesn't look the same if I stop and then resume partway through? Or should it look fine so long as I included Velocity?
    2. Should I be using the "Restore" button to resume a resimulation, or is that button only for original simulations and not resimulations? What is the best workflow for stopping/resuming resimulations?
    3. I have some keyframes set in the original simulation and source, i.e. the discharge animations down to 0 at a certain point, and the smoke dissipation animates up. Should I delete these keyframes before running the resimulation? Or would that cause problems by changing the original Dynamics/Source parameters?

    Thanks in advance for your help!
    Eric Carlsen, Animator & Designer
    http://www.ecarlsen.com

  • #2
    Also, since I have the Velocity channel included, would it be preferable to resimulate with "Use Time Bend Controls" unchecked, and using the "Velocity" blend method, as opposed to using time bend controls? I'm hesitant to do so because the help doc indicate that the Velocity blend method can cause flickering when slowing down a simulation.
    Eric Carlsen, Animator & Designer
    http://www.ecarlsen.com

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    • #3
      Hey,

      Yes, you need to use Restore like in a regular simulation - changing the Start Frame will simply start the resimulation anew from that frame.

      Regarding the keyframes you have - you need to use Max's re-scale time function, and in general the entire procedure described here: https://docs.chaosgroup.com/display/...Time-Scale,etc.

      In case you have Use Time Bend Controls unchecked, you won't be retiming using the resimulation - your resimulation will produce one cache per each regular simulation cache and then the Time Bend controls from the Input panel will be applied during preview or rendering to mix your resimulated caches using the Blending Method you specified, which will work less pretty

      Hope that helps
      Svetlin Nikolov, Ex Phoenix team lead

      Comment


      • #4
        Thanks, this did help!
        Eric Carlsen, Animator & Designer
        http://www.ecarlsen.com

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