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Blob detection troubleshooting

The following topics offer solutions to commonly encountered blob detection issues.

❙       Many blobs on the face or brim have not been detected.

❙       Many blobs have been detected that are not true blobs.

Many blobs on the face or brim have not been detected.

In the Blob Parameters section of the Properties pane, ensure that the following parameters have been set appropriately:

❙       Check that you are detecting the right color of blobs for your marker/ brim setup, and if necessary, select Find Black Blobs and/or Find White Blobs.

❙       Check that the White Min Radius, White Max Radius, Black Min Radius, and Black Max Radius parameters are set correctly. The minimum radius must be low enough not to reject small blobs, and the maximum radius must be high enough to include all true blobs.

❙       Check the Black Threshold and White Threshold. The default value of 0.4 generally finds most blobs, but you may sometimes need to lower this value.

Note that under extreme lighting conditions, where the take appears either very dark or completely saturated (white), blob detection will not be possible.

Many blobs have been detected that are not true blobs.

A moderate number of false blob detections will have no adverse effect on the final tracking results, so unless the effect is very noticeable, you can probably simply ignore this problem.

If Vicon CaraPost is displaying a large number of unwanted blob detections, in the Blob Parameters section of the Properties pane, ensure that the following blob parameters have been set appropriately:

❙       Check the White Min Radius, White Max Radius, Black Min Radius, and Black Max Radius. If the minimum radius is set too low, the blob detector may detect lots of false small blobs, and similarly, if it is set too high, the detector may detect large false blobs.

❙       Check the Black Threshold and White Threshold. The default value of 0.4 generally finds most blobs without detecting many false blobs, but you may sometimes need to raise this value.