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title: "Resimulation"
canonical: "https://documentation.chaos.com/space/PHX4MAYA/125866496/Resimulation"
format: markdown
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This page provides information on the Resimulation rollout.
## **Overview**
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Resimulation is a process that uses existing cache files (with exported [Grid Velocity](https://docs-chaos.atlassian.net/wiki/spaces/PHX4MAYA/pages/126029700/Output#OutputGridChannels)) as a base for a new simulation pass. It works differently for Fire/Smoke and Liquid simulations.
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> You can resimulate over the already resimulated cache files. By default Phoenix reads from a cache sequence and creates another resimulated cache sequence. But you can also use the same path as Resimulation Input and Ouput and overwrite the simulated cache sequence each time you run a new resimulation. For example, this way you can keep increasing the resolution every time you run a new resimulation, and repeat this many times.
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> Due to the difference between the compression algorithms used by Phoenix's AUR format and the OpenVDB format, the resimulation process may produce a different result when using exported VDB caches as opposed to Aura caches if the Storage Quality option in the [Output](https://docs-chaos.atlassian.net/wiki/spaces/PHX4MAYA/pages/126029700) is not the maximum 20 (i.e. is not Lossless).
Enable **Velocity** in the [Output ](https://docs-chaos.atlassian.net/wiki/spaces/PHX4MAYA/pages/126029700)rollout. If you are going to add **wavelet turbulence** as well, also enable the export of the **Wavelet **channel.
Start the original (base) simulation and let it run through.
Enable **Particle Resimulation **or **Grid Resimulation**. Adjust the resimulation options in this rollout if needed.
Start the simulation again - this time the **Resimulation** will take place. You can switch between preview and render of the base and resimulated caches by enabling/disabling the **Resimulate** checkbox.
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> UI Path: ||Select [PhoenixFDSim](https://docs-chaos.atlassian.net/wiki/spaces/PHX4MAYA/pages/125895496)|| **> Attribute Editor > Resimulation rollout**
## **Parameters**
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### **Particle Resimulation**
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### **Grid Resimulation**
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### Time Bend Resimulation
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Phoenix has many tools for changing the animation timing of a cache sequence after it is simulated. Resimulation with enabled Time Bend Controls can produce smoother playback in cases where the [Input](https://docs-chaos.atlassian.net/wiki/spaces/PHX4MAYA/pages/125995816) Time Bend controls are insufficient. For more information on Resimulating with Time Bend, see the Tips and Tricks topic on [How to slow down a simulation, animate the time scale, etc](https://docs-chaos.atlassian.net/wiki/spaces/PHX4MAYA/pages/126028463/Tips+and+Tricks#TimeBendResim).
**Resimulation Cache**
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> 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**.
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> For information on changing the default paths for resimulation, see the [Tips and Tricks page](https://docs-chaos.atlassian.net/wiki/spaces/PHX4MAYA/pages/126028463/Tips+and+Tricks#ResimPaths).
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> 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. This way you can increase the resolution more and more each time you start a resimulation.
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> The following error message may appear when you start a re-simulation:
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> "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."
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> 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.