Varjo Markers
Note: you are currently viewing documentation for a beta or an older version of Varjo
NOTE: This feature is released as Beta in 2.2. In practice, “Beta” means imperfect tracking quality and there may be small issues with the feature overall.
Varjo Markers main purpose is to track static or dynamic objects in user environment using XR-1 Developer Edition’s video pass-through cameras. Application can use multiple trackers to track single object for added precision, for example tracking monitor by placing Tracker in every corner. Varjo Trackers could be used both for MR and VR applications - you don’t need to enable MR mode if you don’t use it.
This marker documentation helps you to understand the visual markers being used by the Varjo Marker tracking. A native code example related to this documentation can be found on the Varjo SDK Examples page. Later, we will introduce the Unity and Unreal examples for this feature.
Varjo Markers
Varjo tracking uses a predefined set of markers for the tracking. These markers are available as printable documents in the table below. The markers have unique IDs. You should not use the same marker more than once in any given environment. There is a selection of different types and sizes of markers which we will go through next.
Marker Sizes and Tracking Distance
Varjo Marker tracking works better with large markers. We recommend using larger markers for good tracking quality when the distance between the marker and the headset is great. Usually, it is the best option to use as large a marker as possible. Below is the list of markers and their recommended maximum distance from the headset when the marker is being tracked:
25mm (~1”) Good in distances up-to 0.5 meter (1.5 feet)
50mm (~2”) Good in distances up-to 1 meter (3 feet)
150mm (~6”) Good in distances up-to 3 meters (9 feet)
Printing Varjo Markers
Marker documents can be used to print the markers used by the Varjo Marker system.
We have 50 pieces of each type and size of the markers in the documents.
| Marker size | Contents | PDF, A4 size | PDF, Letter size |
|---|---|---|---|
| Small markers | 50pcs x 25mm (\~1”) | Download | Download |
| Medium markers | 50pcs x 50mm (\~2”) | Download | Download |
| Large markers | 50pcs x 150mm (\~6”) | Download | Download |
Printing instructions
- Print on matte paper using matte ink to avoid reflections. Inkjet and pigment printers are suitable; however, laser toner is not recommended.
- Print the markers in the darkest and fullest black possible. Rich black (made up of CMYK) is preferable to greyscale (100% K) as the contrast is better for camera recognition.
- Print on one side of the paper.
- Print at 100% scale (actual size) with no additional sizing optimizations, i.e., not fit-to-page. To confirm the sizing is accurate, lay a ruler against the guides on the printout.
- Cut the marker along the crosses and lines, leaving the white margin around the marker.
- Ensure that the marker is flat, and the paper has not curled when using.
- Printing in the wrong size will be noticeable as the virtual marker will be skewed in relation to the real marker.
Other Topics
Performance
Currently, the Varjo Marker tracking system uses single CPU core when it is enabled through the developer API.
Usage tips
- Using more than one marker can increase tracking accuracy. This is especially useful for tracking big area or large objects, where one marker may always not stay in camera view, or if object is observed from different angles.
- If an object can be rotated, use markers on all sides of the object. For example, for a large box that will be observed from all sides, place 4 markers on each side of the box.
- Do not bend the markers - always place them on flat surfaces. Curved marker’s size may be incorrectly detected, and their positional tracking may suffer.
- Varjo markers are cheap replacements for electronic trackers (for example Vive Trackers). However, cost per printed tracker is significantly lower and it does not require power to operate.
- Decreasing light reflections on the markers will result in better tracking.
FAQ
Q: Can I use Varjo Markers to create objects like tracking cubes? A: Yes, it is possible to make a group from Varjo Markers. This means that it is OK to create a cube from unique markers. We are working on a way to define the set of markers for the cube in API to improve the tracking quality of pre-defined marker groups.
Q: Can I use Varjo Markers on a curved surface? A: Varjo Markers are not recommended to be used on curved surface. If you need to put marker on a curved surface, first stick it to flat surface (cardboard) and attach that surface.
Q: How to check if Varjo Markers are printed in correct size? A: If the marker size is incorrect, the distance of the object gets estimated incorrectly. Especially in small markers, even a 1 mm (0.03 inches) difference in size may cause a tracking to shift about one centimeter (0.3 inches).
Q: My Varjo Markers positional tracking is unreliable. The virtual objects stutter or don’t stay at their place. A: Check the recommended distances for different marker sizes. At the upper limit of the recommended distance range the positional tracking may get worse. Choose a larger marker in that case.