Change processing parameters

When the distance between between a centroid and the projection of the corresponding 3D point (model point or unlabeled reconstruction) is too high, the centroid is not associated with that point.

In situations where the true calibration has drifted since the camera calibration process was last run, these distances will become too large and consequently the centroid connectivity score for multiple cameras may start to drop.

To allow the system to tolerate larger than usual image errors and enable those centroids to be associated with the 3D points, and thus contribute to the tracking, change the following parameters in the Processing panel.

Environmental Drift Tolerance

• Reconstruction section> Environmental Drift Tolerance

This parameter applies to the formation of unlabeled reconstructions (which are used to boot objects) and is an uncertainty applied (in mm) to camera calibration to tolerate drift in the calibration due to environmental factors such as temperature change.

When unlabeled reconstructions appear to be noisy, with multiple "ghost" reconstructions appearing close to the true 3D point, centroids that should be associated with the same 3D point may not be associated and thus multiple reconstructions are formed.

In this case, increase the Environmental Drift Tolerance until the ghost reconstructions disappear, ie, all the centroids are correctly associated with a single reconstruction.

Reprojection Threshold

• Object Tracking section > Reprojection Threshold (Advanced parameter)

This threshold (in pixels) is used during tracking when forming correspondences between centroids and model points. If the camera calibration has drifted and correspondences are being missed, increase this value.

Reprojection Threshold is closely related to the Automatic Bias compensation machinery (see Auto Bias Handling). When this is active, the effective value of this threshold is modified automatically.

If ghost reconstructions are visible close to a model point, this may indicate that the Reprojection Threshold is too low. Increasing the parameter has a similar effect to increasing the Environmental Drift Tolerance, whereby the centroids are now associated with a single 3D point (in this case the model point).