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Phoenix FD has many tools for changing the animation timing of a cache sequence after it is simulated. The Input rollout has a variety of animation controls in the Time Bend section where you can change the speed of the animation, loop, or directly animate the cache index for each timeline frame. When using these controls, Phoenix FD Phoenix FD often needs to internally blend between two cache files to produce a given frame on the timeline. The Time Bend Controls blend cache files on the go, at the moment when a new frame is loaded on the timeline - either while you're previewing the simulation in the viewport, or when rendering. For fire/smoke simulations, if you don't want this slowdown, you can bake a new sequence of re-timed caches using Time Bend Resimulation, as described below.

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  • Enable Velocity export in the Output rollout. This channel is necessary for resimulation.

  • Simulate your base simulation. For best results, the Steps Per Frame option must be at 1, not higher.

  • When the simulation finishes, you can adjust your Time bend controls from the Input rollout to the way you desire. You can change your play speed, set it to loop mode or animate the play speed using the direct cache index mode to get a bullet time effect.

  • Do not change any settings in the Dynamics rollout after your base simulation if you want to get a correct Time Bend Resimulation. You can experiment, of course, but results will typically have flickering or distorted playback.

  • From the Resimulation rollout, enable Grid Resimulation and enable Use Time Bend Controls. You . Note that when Resimulation is enabled, the viewport will show the resimulation caches and will not show the base simulation anymore - you have to uncheck Resimulation in order to preview your base caches. Now you can increase the Amplify Resolution or leave it at 0. You can also add If you use amplification ("up-res"), you can also add wavelet turbulence, if the Wavelet channel was exported in the base simulation. It's okay to do a retime using the Time Bend controls together with an up-res in one resimulation.

  • If Play speed in the Input rollout is a constant value, use 3ds Max's 'Re-Scale time' option to stretch the animations in the scene so that they match your speed. E. If g. if you want a Play Speed of 0.2, scale the scene time 1/0.2 = 5 times. This applies both to animated obstacles, emitters, particles, and also to any keyframed options in your Phoenix Sources or Simulators.

  • You can choose between two methods of Time Bend in the Resimulation rollout depending on the result you need. Note that both methods work best for simulations with Steps Per Frame set to a value of 1:

    • The General-Purpose method can deal with all kinds of play speeds - both above and below 1, as well as playing backwards. This method runs fast, but may produce some flickering or motion jitter;. It does not need your scene to be intact, unlike the Slow Down method - e.g. you might have missing emitters, sources, forces, obstacles, or some of your animations or keyframed options might not be retimed, and the General-Purpose method should be able to work even this way.

    • The Slow Down method works well only when your play speed is between 0 and 1, but will provide smooth playback without jittering or flicker. This method may produce more dissipation, so it's good to combine it with Multi-pass advection for fire/smoke. For this method the entire scene must be intact, all interacting nodes from the base simulation must be present, and all animations and keyframed options must be retimed as well.

  • Disable all unused output channels before starting the Resimulation from the No-Export Channels option in the Resimulation rollout. This will reduce the cache file size and speed up the resimulation.

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