OptiTrack

Overview

The OptiTrack device receives live motion-capture data from OptiTrack cameras, streamed by NaturalPoint's Motive software over the NatNet protocol. Onlyview reads the position and orientation of the rigid bodies defined in Motive, so that a 3D object, a followspot, or any other value can follow a performer or a moving stage element in real time.

The device is created once per Motive machine, and every machine of the show — Producer and Media Servers alike — connects to Motive directly rather than relaying the data internally. This keeps the tracking latency as low as possible, but it does mean that the Motive machine must be reachable from all of them.

Info

Only rigid bodies are read. Individual markers, marker sets and skeletons streamed by Motive are ignored.

The device is available on Windows only.

Setup

Motive IP: The IP address of the machine running Motive.

That is the only setting. Onlyview locates the Motive server automatically at that address and picks up the rest of the connection parameters — command port, data port and multicast address — from Motive itself, so there is nothing else to enter on the Onlyview side. Nothing has to be installed alongside Onlyview either: the NatNet runtime is shipped with it.

Motive configuration

For the connection to succeed, in Motive's data-streaming settings:

Enable streaming must be on. Onlyview discovers the Motive server through its NatNet announcement; if streaming is off, the device never connects.
The transmission type must be Multicast. Onlyview joins the multicast group advertised by Motive, and does not support unicast streaming.
Rigid bodies must be included in the stream, and each one needs a streaming ID. That ID is what you enter in the ActionGraph node.
The Up axis should be set to Y Up. Onlyview uses the streamed coordinates exactly as they arrive, in metres, without any axis or unit conversion, and its own 3D world is Y-up.

The Motive machine and the Onlyview machines must be on the same network: the discovery announcement and the multicast stream both have to reach them.

Warning

Onlyview connects to Motive when the show starts. Start Motive and enable streaming first; if the server cannot be found within about a second, the device stays disconnected until the show is reloaded.

The OptiTrack device can be placed on a UserScreen. It shows the device name, the configured Motive IP, and one small square per rigid body currently present in the stream, labelled with its ID. The square tells you whether that rigid body is being tracked or has been lost — a quick way to check, during a show, that the markers are still visible to the cameras.

ActionGraph Nodes

OptiTrack

Outputs the current position and orientation of one rigid body. Available under Devices/OptiTrack in the node palette.

Properties:

Device: The OptiTrack device to read from.
RigidBody ID: The streaming ID of the rigid body, as defined in Motive.

Output Slots:

Position: Vec3 — the position of the rigid body, in metres, in Motive's coordinate system.
Rotation: Quat — the orientation of the rigid body.

Both outputs are invalid when no device is selected, when no rigid body with that ID is present in the stream, or when the rigid body is not currently tracked — for instance because its markers are hidden. Downstream nodes therefore stop updating rather than jumping to a wrong position when tracking is lost.

Use one node per rigid body you want to follow.

Info

Tracking data usually arrives ahead of the video it has to match. To realign it with the rest of the show, insert one of the Delay nodes — the Delay (Vec3+Quat) variant delays a position and a rotation together, keeping them synchronised.

OptiTrack

Overview

Setup

Motive configuration

Device Widget

ActionGraph Nodes

OptiTrack

See also