Unity AR demo using ViSP

1. Using ViSP Unity wrapper in Unity engine

This project contains in unityProject folder 2 demos that illustrate ViSP Unity wrapper usage. From here we suppose that you followed the previous tutorial that shows how to build ViSPUnity plugin that was installed in $VISP_WS/visp_unity/unityProject/Assets/ folder if you are under Linux/MacOS or in %VISP_WS%\visp_unity\unityProject\Assets\ folder if you are under Windows.

Start Unity engine and open $VISP_WS/unityProject
The generated ViSPUnity plugin should be visible in the Assets folder

36h11 AprilTag can be downloaded from here.
In Assets > Scenes window you should see 2 scenes corresponding to AprilTag Augmented Reality demo and Generic Model-Based Tracking demo respectively

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2. Unity demonstrations using ViSP

2.1. AprilTag Augmented Reality demo

For the first project, go to the folder Assets/Scenes and open scene_ar by double click.

You should have a similar Unity window opened, as shown below:

Click on the Plane GameObject in hierarchy and in the inspector window modify some demo settings:
- The Tag_size value according to you printed tag size. This value corresponds to the dimension of the black square in meters.
- Optionally you can also modify the values of your camera parameters obtained after camera calibration.
- If you have more than one camera attached to your computer, use Camera_id to select the camera to use. In the Console panel there are some logs that may help to identify each camera id.
- Note also the Debug_display option that is disabled by default. If enabled it will open a windows in which the current image is displayed with computer vision results that may be useful to understand the low level processing achieved with ViSP.

Notice that the gameObject Cube is a child of gameObject Cube_pivot. This is done to make sure that the cube rotates around the center of one of the faces.
The current implementation takes care of position, scaling and rotation of the cube. A small YouTube Video demonstration is also available here.

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2.2. Generic Model-based Tracking demo

For the second project, go to the folder Assets/Scenes and open scene_mbt by double click.

You should have a similar Unity window opened, as shown below:

For this demonstration, we are using a 7cm x 7cm x 7cm cube made from cardboard. A 36h11 AprilTag (4.8cm x 4.8cm) is pasted on one of its faces for tracker initialisation. We strongly recommend to put texture on the other cube faces so that the tracker benefits from keypoint features. Here is a picture for reference:

Click on the Plane GameObject in hierarchy and in the inspector window modify some demo settings:
- The Tag_size value according to you printed tag size glued on one cube face. This value corresponds to the dimension of the black square in meters.
- The Cube_size value according to your cube.
- Optionally you can also modify the values of your camera parameters obtained after camera calibration.
- If you have more than one camera attached to your computer, use Camera_id to select the camera to use. In the Console panel there are some logs that may help to identify each camera id.
- Note also the Debug_display option that is disabled by default. If enabled it will open a windows in which the current image is displayed with computer vision results that may be useful to understand the low level processing achieved with ViSP.

Now, click play button to start. A small YouTube Video demonstration is also available here.

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3. Tips & Tricks

3.1. Unity crashes on MacOS

This issue comes from MacOS camera authorization requested before usage in Unity.

The work around is to quit Unity Hub and launch it from a terminal:

$ /Applications/Unity\ Hub.app/Contents/MacOS/Unity\ Hub

If this is not enough, try to quit properly your opened applications and restart your computer.

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3.2. DllNotFoundException: ViSPUnity

Check if in $VISP_WS/visp_unity/unityProject/Assets/ there is the ViSPUnity plugin named ViSPUnity.dll under Windows, ViSPUnity.so under Ubuntu and ViSPUnity.bundle if you are on OSX.
If the file is missing, it means that you forget to call make install after building vispWrapper project as explained in the previous tutorial.
If the file is present, quit Unity, start Unity and try to run again unityProject.

When you change the code in vispWrapper project and do a fresh installation using make install that copies the bundle in the unityProject/Assets folder, you should quit and restart Unity to reload the modified plugin.