General


Re-simulation uses an already simulated cache sequence with exported velocity (base simulation) to drive a new simulation with any of these added effects:

  • Increase resolution while keeping the shape and behavior (it's possible to add wavelet turbulence to increase detail or simply amplify the resolution).
  • Change foam/splash settings without touching the liquid grid.
  • Slow down or speed up the animation, as well as apply animated time scale.

If you want to setup your rendering and simulation cache paths manually, please make sure to check the articles on simulation paths and resimulation paths.

When performing a Resimulation, it is recommended to leave the Dynamics settings unchanged between running a base simulation and resimulation. However, any changes to the Dynamics parameters will be reflected during a resimulation, in case a more advanced behavior is desired.

Base Simulation

Re-simulated with Amp. Resolution=1

and 'Wavelet Nice' Method

Parameters


Particle resimulation

Enable (MXS:resim_resimulate_particles) - Enable/disable the particle resimulation. You can use this option when you are satisfied with the liquid behavior, but you want to add or change the foam or splash. The Particle resimulation will produce the exact same result as the base simulation only with Steps per Frame = 1. With a higher number of steps, the intermediate steps cannot be reconstructed and a full simulation is needed to match them exactly, while the resimulation is only approximate.

With liquids, this mode can help to separate the liquid mass simulation from the foam and splash simulation, in order to save time and allow independent adjusting. First, the base liquid sim is iterated without foam and splash, until a satisfying liquid mass behavior is reached. Then, one can proceed to resimulate the foam on splash on top of the liquid, adjusting the particle amount and behavior.

Grid resimulation

Enable (MXS:resim_resimulate_grid) - Enable/disable the grid resimulation. Use this option when the grid detail has to be improved by increasing the resolution and by eventually adding wavelet turbulence.

Amplify Resolution (MXS:resim_ampres ) - Increases the grid resolution a specified amount of times. 0 means "no change", 1 means "x2", 2 means "x3", etc. Non-integer values can also be entered, however they are slightly slower to calculate. The resolution can also be decreased by using a negative value.

Amplify Method (MXS:resim_ampmeth) - When the grid resolution is increased, specify which method to use to sample the velocity.

  • Interpolate - Use interpolation - the velocity channel is simply stretched from the lower resolution to the increased one.
  • Wavelet Fast - Use wavelet turbulence to synthesize fine detail. Needs a Wavelet channel exported from the base simulation. This is a slightly faster approximation method.
  • Wavelet Nice - Use wavelet turbulence to synthesize fine detail. Needs a Wavelet channel exported from the base simulation.


Wavelet Strength (MXS:resim_wvstr)
 - Specify the strength of the wavelet turbulence.

Wavelet Cutoff (MXS:resim_wvcut) - Turbulence with smaller amplitude will be cut off (i.e. helps for faster resimulation).

No-Export Channels (MXS:resim_tmpchan) - Specify the channels that are used just for resimulation and must not be exported to the resimulation output cache. For example when you are doing wavelet turbulence, you will want to remove the RGB/Wavelet and Velocity channel from the final simulation to reduce the cache size.
 

Time Bend Resimulation

Check the topic on How to slow down a simulation, animate the time-scale, etc. for more information.

Use Time Bend Controls (MXS:resim_grid_timebend) - You can change the time scale of the base simulation according to the Time Bend settings in the Input panel. You need to re-scale the time of all other interacting objects and sources in the scene as well - during re-simulation sources and obstacles still work. If your play-speed is constant, you can use 3ds max's Re-Scale Time feature.

Time Bend Method (MXS:resim_grid_timebend_method) - A method to use when scaling the time of the resimulation. Note that both methods work best when Steps per Frame is set to 1:

  • General-Purpose - This method works for all play speeds including backwards playback. It works fast, but may produce flickering or jittering movement of the fluid.
  • Slow Down - This method works only for play speed between 0 and 1. It will produce smooth playback without flicker or jitter, but will add more dissipation in the long run, so it's better to combine it with the Multi-Pass Advection.
Input Play Speed = 0.2, Interpolation BlendSlow Down method + WaveletGeneral-Purpose method + Wavelet


Resimulation cache

Wait if caches are missing (MXS:resim_cachewaiting) - Wait if the base cache file is not yet available. This can be used if another instance of 3ds Max is simulating the base cache at the same time (on the same or other computer).

Input Simulation Path (MXS:resim_inpath) - Specify the base simulation caches whilch will be used as base for resimulation. $(same_as_output) by default.

Output Simulation Path (MXS:resim_outpath) - Specify the path for the output cache files. See Output Path for details. $(scene_dir) by default (will append "_resim" to the end of the file name).

Phoenix FD will not prevent you from overwriting the original input cache! If you don't have enough disk space, it's a valid option to do so.

 

You can find more information on how to setup your resimulation paths in this topic.

 

 


 

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