3D Extensible tracking

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Introduction

The 3D Extensible Tracking in Unifeye allows the generation of a 3D map of the environment "on the fly". This means, that a 3D map of the environment is created based on the pose provided by a starting tracking system and then constantly extended while tracking. The starting tracking system is used for as long as it is available. If the starting tracking system is lost, the 3D map is used for tracking until the starting tracking system is available again. The 3D map can also be used for relocalisation after the tracking has been lost entirely. This means that if you loose the tracking while the 3D map is being used, you can but you don't necessarily have to go back to the starting tracking system. The tracking will start again as soon as enough features stored in the 3D map are located again or the starting tracking system delivers valid tracking values again.

The 3D Extensible Tracking is well suited if you want to use a certain tracking system (e.g. Marker Tracking or 3D Markerless Tracking) but you need to move around a bit and don't want to pay too much attention to not loosing the tracking target but instead concentrate on your main task. This is very useful in scenarios such as AR-supported maintenance. The Extensible Tracking does not only provide you with some extra moving space but also adapts the 3D map to changing lighting situations.

Configuring the starting point

Generally any tracking system offered for the Unifeye system can be used as starting point. For most usecases it will be either Marker Tracking or 3D Markerless Tracking. If you need any other tracking system as starting point, please contact the metaio support team.

Marker-based starting point

One marker at least has to be placed in the environment that needs to be reconstructed and used for tracking. Please note that markers must be attached to planar surfaces. The markers allow the reconstruction tool to generate a map at the correct scale and make it possible to recover the camera pose with respect to the environment. Once the set of markers to be used has been chosen, the user needs to configure the markers, i.e. create a Tracking Configuration file that contains the different markers IDs and sizes. If multiple markers are used they should be calibrated correctly. This means that in the tracking configuration file, the correct COS offset should be set.

For information on how to create markers a marker tracking configuration file, please have a look at the documentation for the Marker Tracking Configuration tool. A marker tracking configuration file defining one coordinatesystem represented by a single marker might look as follows:

To use this marker as a starting point for 3D extensible tracking open this tracking configuration file in an editor of your choice to make the following additions:

• A FeatureBasedSensorSource has to be added to the Sensors section

  • The SensorID can be freely chosen

  • The TrackingMethod tag has to be set to Markerless3D

  • The UseExtensible3DTracking tag has to be set to 1 (which means it is enabled)

  • The SensorCosID can be freely chosen

  • The referenceFeatures tag has to be empty (because we don't want to use an existing map as starting point)

• A SendTo definition has to be added to the Markertracking SensorSource in the Connections section. (This defines the marker as starting point for the extensible tracking.)

  • The SensorID has to be the same as the one chosen for the feature based sensor source above

  • The SensorCosID has to be the same as the one chosen for the COS of the feature based sensor source above

• A SensorSource definition has to be added to the COS definition in the Connections section

  • The SensorID has to be the same as the one chosen for the feature based sensor source above

  • The SensorCosID has to be the same as the one chosen for the COS of the feature based sensor source above

Note: If several Markertracking SensorSources are connected to the COS, you have to add the SendTo tag to all of them.

3D map-based starting point

First, you have to create a 3D map as described in 3D Markerless Tracking.

Then, you create a new tracking configuration file using an editor of your choice. The configuration file has to contain:

• A FeatureBasedSensorSource in the Sensors section

  • The SensorID can be freely chosen

  • The TrackingMethod tag has to be set to Markerless3D

  • The UseExtensible3DTracking tag has to be set to 1 (which means it is enabled)

  • The SensorCosID can be freely chosen

  • The referenceFeatures tag has to contain the path to the 3D map you've created with the Markerless Tracking Map Generator (because we want to use it as starting point)

• A SensorSource definition within the COS definition in the Connections section

  • The SensorID has to be the same as the one chosen for the feature based sensor source above

  • The SensorCosID has to be the same as the one chosen for the COS of the feature based sensor source above

If you load this tracking configuration file into Unifeye, the 3D map created with the Markerless Tracking Map Generator will be used as starting point and then this same map will be extended "on the fly".

Using 3D extensible tracking configuration files in Unifeye

To activate the 3D extensible tracking in Unifeye, just load a tracking configuration file created as explained above using the Tracking Configuration Tool:

Note: There is an example 3D extensible tracking configuration file called AS_Tracking_Data_3D_Extensible.xml in UnifeyeInstallationFolder-->config-->SensorSources

→Return to Tracking Configuration

-- SupportMetaio - 2011-01-21