Circle markers are created with an application called MarkerFactory. This application produces png files that include a circular 2D marker, as below:
These markers are then printed onto paper or card, and used on the screen.
Options to the MarkerFactory are:
–code number, the code value, as normal decimal number, default: 0–blocksize number, the size of each block in pixels, for minimum size use 16 (the default is 100).–division number, the number of rows/columns of actual data, default: 4-o filename, the output filename, default: code-XXXXXX.png, where XXXXXX is the number in the codeFor example to create the marker above (code 372), one would run:
MarkerFactory --type circle --division 2 --code 372
The division parameter affects the amount of data that the marker can hold. The current display firmware can only read circle markers with 2 rings of data.
Marker size
The physical size of the markers is limited by how well the computer vision can determine the marker shape. At the center of the camera image the camera resolution is better (due to lower diffusion). On MultiTaction hardware, the minimum width of a single cell is around 5 millimeters. There should also be 5 millimeters of empty white space around the marker. The table below lists some typical marker sizes and the number of unique markers they can represent:
| Marker division | Bits | Unique codes | Minimum size |
|---|---|---|---|
| 2 | 9 | 512 | 3.5cm x 3.5cm |
| 3 (not yet available) | 19 | 524288 | 4.5cm x 4.5cm |
| 4 (not yet available) | 29 | 536870912 | 5.5cm x 5.5cm |
| 5 (not yet available) | 51 | 2.25 billion | 6.5cm x 6.5cm |
The center of the marker is counted as the first ring. The edge of the marker also carries one information bit.
MarkerFactory application
MarkerFactory application is included with the Cornerstone software packages which are available in the Download section. The location of the application binary depends on the platform: