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create-markers.md

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Create Markers

Motivation

Before tracking markers with your camera, you need to create, print and place them in the environment. You can use four type of Aruco objects: markers, grid boards, charuco boards and diamond markers.

Aruco Objects

From left to right: a marker, a diamond marker, a grid board, a charuco board.

CreateMarkers scene

Open the Assets/ArucoUnity/Scenes/CreateMarkers.unity scene to visualize the Aruco objects. Play this scene to create them. You can find the created images in Assets/ArucoUnity/Images/.

Manual creation

Marker

Create a marker

Manual creation and configuration of a marker.

  1. Create an empty object.
  2. Add a ArucoMarker script. Configure it:
    • Select a dictionary of markers. It determines the marker size (for example 4x4 bits) and had a size (for example 50 markers). A lower dictionary size is better to avoid detection errors. For more details, see "Markers and Dictionaries" and "Selection a dictionary" sections of this tutorial.
    • Set MarkerSideLength in pixels. It controls the image size.
    • Set MarkerBorderBits with a minimum of 1. It controls the width of the black border of the marker, helping its detection.
    • Set MarkerId, from 0 to the dictionary size.
  3. Add a ArucoObjectCreator script. Configure it:
    • Add the ArucoMarker script to the ArucoObject field.
    • Check DisplayInPlayMode if you want to display the marker in play mode.
    • Check SaveImage to save the marker in an image file in play mode.
    • Set the OutputFolder path to save the image, relative to the persistentDataPath in builds or to the "Assets" folder of your project in the editor.
    • Check AutomaticFilename for an automatic image filename based on the ArucoObject property values.
    • Set the image filename in OptionalImageFilename if AutomaticFilename is not checked.
  4. Play the scene. The marker is automatically created on a child plane of our object and saved on the project folder.

Grid board

Create a grid board

Example of a grid board with the corresponding configuration.

The process is the same as in the marker subsection.

The additional configurable parameters are:

  • MarkersNumberX: The number of markers on the board X axis.
  • MarkersNumberY: The number of markers on the board Y axis.
  • MarkerSeparation: The margin between markers in pixels.

Charuco board

Create a charuco board

Example of a charuco board with the corresponding configuration.

The process is the same as in the marker subsection.

The additional configurable parameters are:

  • MarginLength: The markers margin on the white squares.
  • SquaresNumberX: The number of squares on the board X axis.
  • SquaresNumberY: The number of squares on the board Y axis.
  • SquareSideLength: The width in pixels of each square.

Diamond marker

Create a diamond marker

Example of a diamond marker with the corresponding configuration.

The process is the same as in the marker subsection.

The additional configurable parameters are:

  • SquareSideLength: The width in pixels of each square.
  • MarkersXId: The ids of the four markers.