This page provides information on the Resimulation rollout for a LiquidSim object.
Overview
Liquid Resimulation uses an already simulated cache sequence and allows you to add, delete or modify the Splash, Mist, Foam or Wetmap particle systems. It will preserve the Liquid and the particle systems you are happy with.
The particle resimulation will affect only the particle systems which are checked in this rollout. If a particle system is not checked, it will remain unchanged. The Liquid always remains unchanged. While the Fire/Smoke Resimulation by default creates new cache files during the simulation process, the Liquid Resimulation overwrites the existing cache files.
Using Resimulation to just modify a particle system is practical only in case you have a large number of secondary particles such as Foam, Splash, etc. in relation to the number of Liquid particles. Otherwise, if you have mostly Liquid particles and very few other particles, it will be faster to just simulate over again.
Additionally, the scene must be intact between running the base simulation and the resimulation. Please do not remove any Sources and their emitters, obstacles or forces that interact with the simulation.
Select Resimulation → Particle Resimulation → Enable and select the respective particle system below (i.e. Splash and Mist, Foam or Wetting).
Modify the particle system's settings - e.g. for Foam, go to the Foam rollout and tweak the parameters there.
Hit Start to run the simulation again - repeat this process until you are happy with the result.
Select Resimulation → Particle Resimulation → Enable and select the respective particle system below (i.e. Splash and Mist, Foam or Wetting).
Make sure the particle system's simulation is Enabled, e.g. for Foam open the Foam rollout → select the Enable option.
Hit Start to run the simulation again - the particle system will be added to the cache sequence.
Select Resimulation → Particle Resimulation → Enable and select the respective particle system below (i.e. Splash and Mist, Foam or Wetting).
Make sure the particle system's simulation is Disabled, e.g. for Foam open the Foam rollout → deselect the Enable option.
Hit Start to run the simulation again - the particle system will be removed from the cache sequence.
UI Path: ||Select Liquid Simulator object|| > Modify panel > Resimulation rollout
Parameters
Expand – Opens a floating dialog that contains the selected rollout and automatically folds the command panel rollout.
Re-Center – Resets the position of the floating rollout.
? – Opens up the help documents for the Liquid Resimulation.
Start Frame
- From Simulation | rs_start_from_sim – When enabled, the Resimulation will run from the first frame of the base simulation to the simulation End Frame or the Custom Stop Frame, depending on the options.
- Custom | resim_startframe - Explicitly sets the Start Frame of the Resimulation. This can also be a negative number.
Stop Frame
- From Simulation | rs_stop_from_sim – When enabled, the Resimulation will run from the base simulation Start Frame or the Custom Start Frame to the last frame of the base simulation.
- Custom | resim_stopframe - Explicitly sets the End Frame of the Resimulation. This can also be a negative number.
Particle Resimulation
Enable | resim_resimulate_particles – Enables/disables the Particle Resimulation.
Splash and Mist | resim_splash – Specifies that the Splash and Mist will be resimulated.
The Affect Liquid parameter on the Splash and Mist rollout will be ignored when resimulating Splash, because the liquid is already simulated and cannot be changed without a full simulation.
Resimulating the Foam on Hit parameter on the Splash and Mist rollout requires Splash and Mist to be resimulated.
Foam | resim_foam – Specifies that the Foam will be resimulated.
Wetting | resim_wet – Specifies that the WetMap particles will be resimulated.
The Sticky Effect setting for Wetting in the Liquid rollout will be ignored when resimulating wetting. This is because the liquid is already simulated and cannot be changed without a full simulation.
Resimulation Cache
During resimulation, Phoenix reads cache files from the Base Cache Files Path, performs resimulation operations, and then saves a new cache sequence in the Output and Render Path.
For more information on how to set up resimulation paths, see the Tips and Tricks page.
Base Cache Files Path | resim_inpath – Specifies the base simulation caches which will be used as base for resimulation. $(same_as_output) by default.
Output and Render Path | resim_outpath – Specifies the path for writing the output cache files. See Output Path for more details on the $(...) macros you can use. $(scene_path) by default (will append "_resim" to the end of the file name).
Click the "..." button to open a menu with the following options:
Browse - Opens a dialog where you can select where the resimulation caches will be written to. The filename you type in must contain # signs so each resimulation frame will be written to a differently numbered file. Also, you can choose between two file formats - AUR and VDB cache files.
Delete Cache Files - Clears the resimulation files.
Reset to Default - Resets the resimulation path to default.
Help - Opens this help page.
You can use the same Output and Render Path as the Base Cache Files Path, and this way Phoenix will not create a separate cache sequence for resimulation, but will overwrite the base simulation caches instead. It's valid to do so if you need a more complicated setup or when not enough disk space is available.
The following error message may appear when you start a re-simulation:
"Cannot start the Re-Simulation! Please make sure the simulation was run with the 'Velocity' channel checked under the 'Output' rollout, and that the cache files in the Simulation Input path exist."
The reason may be that either the files in the Input Simulation Path do not exist at all, or they do not have Grid Velocity Channel exported when you have simulated them beforehand. Of course, you may use more complicated setups where you resimulate over an already resimulated cache file, or you may Load an existing base cache file as the initial state of the re-simulation. These are all possible; you just need to have velocity in the base cache and an existing path to it.