Visualizing Results

This tutorial comes after the tutorial on Setting up and Running Simulations. Please be sure to complete it before going further.

Visualizing Results in Gmsh

Gmsh is a powerful program for 3D visualization. However, it has a somewhat steep learning curve. For this reason, SimNIBS writes .opt files with basic visualization configurations in addition to the mesh files. Here we will give a walk-through of a few useful features in Gmsh.


Gmsh is distributed together with SimNIBS, you don’t need to install it separately.

Starting Gmsh

Gmsh automatically opens when a simulation is finished. Alternatively, you can start Gmsh by double clicking in the ernie_TDCS_1_scalar.msh file or typing in the terminal

gmsh ernie_TDCS_1_scalar.msh

The following window will appear:


We see the gray matter surface with the magnitude of the electric field (magnE), as well as the electrode currents. You can rotate the model with the left mouse button, translate it with the right button, and zoom with the mouse wheel.

Selecting Where to Visualize

To visualize another surface, such as white matter:

  1. Go to ToolsVisibility


and select Elementary entities


  1. Select surfaces and volumes to be visualized. In SimNIBS, we have defined

    1: White Matter volume

    2: Gray Matter volume

    3: Cerebrospinal Fluid (CSF) volume

    4: Skull volume

    5: Skin volume

    6: Eye volumes (headreco models only)

    101+: Electrode rubber layer volume

    501+: Electrode gel / sponge volume

    The corresponding surfaces have the number 1000 + volume value. For example, 1002 corresponds to the gray matter surface. The only exception are the electrode contacts, numbered 2100+. You can select multiple surfaces or volumes by holding Ctrl. Selecting 1001 and clicking on Apply, we can see the white matter surface:


Selecting What to Visualize

You can select the field to be visualized by checking the boxes in the left of the Gmsh window.


To visualize the surfaces or volumes without any field, go to Tools -> Options -> Mesh and click on Surface Faces or Volume Faces


Changing the Scale

To change the scale of a field visualization, select ToolsOptionsView [N] and change the Min and Max values.


Exporting an Image

To create an image, go to File -> Export (or press Ctrl+E) and type in a file name with a .png or .jpg extension.

Other Functionalities

We recommend users to explore the many functionalities of Gmsh. One can, for example, produce the image below by selecting the Volume 2 for visualization an clipping the model in ToolsClipping.


Visualizing Results in MATLAB

To visualize results in MATLAB, add the <SIMNIBS_INSTALL_DIR>/matlab/ folder to your MATLAB path. Afterwards, type


or use


to have more control over the visualization.

Further Reading

For more information on visualization and simulation output, please see the SimNIBS 2.1 tutorial paper.