BlackTrax Overview
BlackTrax
Section titled “BlackTrax”BlackTrax (BT) is a vision-based tracking system available from CAST, capable of tracking both objects and people. BT can provide positional data (3D) or positional and rotation data (6D).
BlackTrax connects to different third-party applications, such as robotic lights, media servers, and others that accept the open RTTrPL/M protocols. Within Designer BT tracking data can be input into and mapped to objects or props.
The BT system uses an array of cameras (typically placed on the stage rig or truss) to observe “stringers”, which are small IR (infrared) LED markers. These active markers are placed in various areas on the talent or prop. They can be identified by the BT cameras via a unique IR pattern. Tracking markers are connected to a BT Beacon, which sends the generated rigid body information via a BlackTrax server to Disguise. As long as a marker is observable by at least two BT cameras, an accurate positional fix is possible.
Each active marker is attached to a small BT Beacon unit, which is usually hidden from view (e.g. attached to the talent’s belt). This unit provides power and control to the IR markers. For full 6D tracking three markers need to be connected to a BT Beacon.
BlackTrax can integrate with Disguise in two ways:
- Actor/talent tracking
- Prop/screen tracking (used for movable scenic pieces)
A BlackTrax server contains the software programs required for configuring a BT system, including BTWYG, BlackTrax, Motive and Server Manager.
Please visit the CAST website and BT FAQs for additional information on using BlackTrax, as well as training courses.
For setup instructions specific to Disguise, please see BlackTrax integration and BlackTrax Motive setup.
RTTrPM
Section titled “RTTrPM”BlackTrax RTTrPM output configuration
Section titled “BlackTrax RTTrPM output configuration”
The BlackTrax real-time tracking system uses RTTrPL and RTTrPM protocols to interface with other lighting and third-party applications (such as media servers, robotic cameras, and spatial audio systems) to provide tracking for automated lights and projection mapping.
BlackTrax RTTrPM
Section titled “BlackTrax RTTrPM”-
BlackTrax sends out RTTrPM packets at a fixed rate of 100Hz.
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BlackTrax by default sends out a heartbeat, or an empty RTTrP header with an RTTrPM signature if no Beacon or LED data is available in the current frame.
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BlackTrax can add and remove different modules at any given time.
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In the BlackTrax implementation of the Trackable module with Timestamp, the Timestamp value is equal to the frame ID of the cameras in the BlackTrax system, as determined by the TimeKeeper.
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Euler Orientation modules always send with an order of
0x0123 (X1, Y1, Z1). -
The Tracked Point modules correspond to the LEDs on a BlackTrax Beacon (trackable), the Index is either
0x01,0x02or0x03. -
The context field in the RTTrP header is always set to the value of the current BlackTrax chapter (0x00000001, etc.), regardless of whether the current Trackable is present in the chapter, or if no Trackables are present in the RTTrPM packet (i.e. just the heartbeat is being sent). When in standby, the Context field is set to 0xFFFFFFFF.
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The Zone Collision Detection module should only send Zone Sub-Modules that the Trackable is actively colliding (inside) with. If a Zone Sub-Module is not sent, it is assumed the collision is not happening and the Trackable is outside of the Zone.