---
title: "Calibrate Dikablis eye tracking in Vicon Nexus"
canonical: "https://help.vicon.com/space/Nexus216/11600217/Calibrate%20Dikablis%20eye%20tracking%20in%20Vicon%C2%A0Nexus"
format: markdown
---
Before capturing an eye tracking trial, you must calibrate eye tracking within Nexus. To do this, complete the following procedures in the order shown.

> Macro (scroll-only)
> 
> > Macro (toc)

## Set up a calibration trial for eye-tracking


    **To set up a Vicon Nexus calibration trial for eye-tracking:**


1. Before you begin a calibration trial for eye-tracking, ensure you have calibrated your Vicon cameras, set the volume origin, and added the Dikablis device to Nexus.
2. Get your subject to enter the volume wearing the head unit with markers, and holding the calibration wand in front of them.
3. In the **Capture** tools pane, in the **Next Trial Setup** section, enter a **Trial Name** (for example, Calibration), and in the **Capture** section, click **Start** to capture a short trial (a couple of seconds).
4. Load the trial you just created (on the **Data Management** tab (F2), double-click on the trial) and on the Nexus toolbar, click the **Reconstruct** button > Macro (inline-media-image)

.
5. In **3D Perspective** view, zoom in so you can see the two objects (subject and wand).

## Create objects for eye tracking in Vicon Nexus

To set up a calibration trial for eye tracking, you need to create wand and head objects.


    **To create the objects in Nexus:**


1. On the **Subjects** resources pane, click the **Create a blank subject** button.
2. In the **Enter Subject Name** dialog box, enter the subject name: `Wand`.
3. On the **Subjects** tab, click the **Wand** object you just created to select it and at the top of the **Subject Preparation** tools pane on the right of the screen, in the **Subject** dropdown menu, ensure **Wand** is selected.
4. In the **Subject Preparation** tools pane, in the **Labeling Template Builder** section, enter a segment name (Wand) in the **Create Segments** box and click **Create**.
5. In a **3D Perspective** view, select the wand markers, beginning with the origin (middle) marker.
6. Ensure all the wand markers are selected.
7. In the **Labeling Template Builder** section, click **Create** again.
8. In the **3D Perspective** view, check the axes and origin are shown for the wand.
9. To create a head object, in the **Subjects** **Resources** pane, click the **Create a blank subject** button and in the **Enter Subject Name** dialog box, enter Head.
10. On the **Subjects** resources pane, click the **Head** object you just created and at the top of the **Subject Preparation** tools pane, ensure **Head** is selected.
11. In the **Labeling Template Builder** section, in the **Create Segments** box, type Head and click **Create**.
12. In the **3D Perspective** view, select the head markers, beginning with the origin marker. For the head's origin marker, select the marker closest to the eyeball, then select the others.
13. In the **Labeling Template Builder** section, click **Create** again.
14. In the **3D Perspective** view, check the axes and origin are shown for the new object.
15. Before proceeding, it is a good idea to save both subjects (Wand and Head). To do this, on the **Subjects** **Resources** pane, right-click on the node for each subject in turn and then click **Save Subject**.

> Macro (scroll-pagebreak)

## Specify Dikablis Eye Tracker device properties

After you have created both the Wand and the Head in Nexus, specify their properties on the **System Resources** tab.

1. On the **System** resources tab, click on the **Dikablis Eye Tracker** node, and in the **General** section of the **Properties** pane, in the **Head Segment** field, enter Head.
2. In the **Eye Offset** section, enter the relevant values (that is, the distance between the origin marker and the eye).
  :check_mark: **Tip**: To find the relevant eye offset values, if your Vicon system includes video cameras, you can use overlay video. If not, you can measure the distance from the origin marker.
3. In the **Calibration Object** field in the **Calibration** section, enter the name of the calibration object (Wand).

You have now set up the eye tracker properties.

## Calibrate eye tracking in Vicon Nexus

After you have added eye tracking to Nexus, created Head and Wand objects, and set the eye tracking properties, you can complete the final steps.


    **To calibrate the eye tracker in Nexus:**


1. On the **System** **Resources** pane, under the expanded **Dikablis Eye Tracker** node, click the **Eye** node to select it.
2. Display a **Data Correction** view, to show both a **3D Perspective** and **Graph** view.
  You should see the x and y values for the selected eye.
3. In the capture volume, place the wand 2–2.5 meters from the subject and get the subject to look at the origin marker (the middle marker at the top of the T).
4. On the **System** **Resources** tab, click the **Dikablis Eye Tracker** node and in the **Properties** pane, go to the **Calibration** section and click **Add**.
5. Move the wand to another part of the volume and click **Add** again.  
In the **Samples** box, 2 is displayed.
6. Repeat the previous step.  
After you have collected three samples, an eye vector and an eyeball are displayed in the **3D Perspective** view.
7. Collect more samples (aim for at least five samples in total) to refine your results.
  :check_mark: **Tip**: When collecting samples, place the wand in the bottom left of volume and have the subject look at the origin marker. Pause for about a second and then in the **Calibration** section, and click **Add**. Then place the wand in the top left of the volume, and have the subject look at the origin marker. Again, pause, and click **Add**. Repeat with the wand at the top right of the volume, and then at the bottom right of the volume. Continue to move the wand and click **Add** until the eye gaze vector accurately tracks the origin marker.
8. When the eye tracker system has been calibrated (and if the subject is looking at the origin marker), in **3D Perspective** view, the eye gaze vector will pass through (or point to) the origin marker of the calibration wand, depending on how far the subject's head is from the wand.
9. View the results in a **3D Perspective** view.
10. To check that the eye tracks the wand correctly, record a short trial.