# Using Paraview

Paraview is an opensource visualization tool developed by Kitware. It provides an intuit and feature rich tool for visualizing simulation data. Kitware provides pre-built binaries that can be downloaded here. Paraview 5.10.1 is the current recommended version.

## Visualize the embedded boundary

The solver will save the embedded boundary if `mfix.write_eb_surface = true` is set in the inputs file as parallel VTP file named `eb.pvtp`. To open the `eb.pvtp` file, press the open button, browse to the simulation directory, select the `eb.pvtp` file, and press `OK`. The `eb.pvtp` will be displayed in the `Pipeline Browser`. Make sure the `eb.pvtp` is selected in `Pipeline Browser` and press `Apply` on the properties tab. The embedded boundary will now be visible in the 3D viewer. The color and opacity of the embedded boundary can be changed on the properties tab.

## Visualize the particles

The solver will write plot files if one of the write frequency options is set (`mfix.plot_int`, `mfix.plot_per_exact`, or `mfix.plot_per_approx`) in directories that are prefixed with the prefix specified in the inputs file (`mfix.plot_file = 'plt'`). To visualize these particles in Paraview, press the open button. In the file dialog, browse to the simulation directory and select the directory group corresponding to the specified prefix. In this example, the director group is displayed as `plt...`. If only one plot directory has been written, select the `plt#####` directory. Press `OK`.

A dialog will popup asking what reader to use. Select the `AMReX/BoxLib Particles Reader` and press `OK`.

Press `Apply` on the properties tab to read the files. To actually see the particles, change the `Representation` from the default `Surface` to `Point Gaussian`. The particles should now be visible in the 3D view.

On the properties tab, the radius of the particles can be changed by moving the slider or editing the value in the `Gaussian Radius` field. The particles can be colored by different variables by selecting the variable in the drop down. Additionally, if a group of plot files was opened, the simulation can be “played” by pressing the play button.

## Visualize the cells

Following the same method to visualize the particles, the cells can be visualized. The major difference is when the dialog asking what read to use is displayed, select the `AMReX/BoxLib Grid Reader` and press `OK`. On the properties tab, select which variables to read (make sure to select `ep_g`, we will use this later) and select apply. Under the Coloring section select `ep_g` to color the cells by this value.

You can open the embedded boundary, particle, and fluid data simultaneously, and change the opacities of the embedded boundary and fluid data to visualize all the data simultaneously.