Flex 13s need to be plugged into Optihubs. If using multiple optihubs, they need to have sync cables between Hub Sync In and Hub Sync Out (Obviously, the cable should run from the OUT of one to the IN of another). Load motive on the mocap computer (must be running windows).
The cameras should appear in the "Camera Preview" Pane. By default, they are in object mode, which means they will appear black with white where they are detecting intense infrared (mocap dots or other cameras). This mode in inconvienant for checking the placement of the cameras. They can be switched to greyscale mode by clicking the gear symbol by an individual camera preview or in the camera tab by clicking the first crosshair symbol at the top of the Devices Pane. It is helpful to place a large, visible object (ex. chair) in the center of your mocap area so you can get a better idea of whether your cameras are aligned well while looking at the computer. Another person also works. Make sure there is enough overlap (around 3 camera minimum) in all regions in your area.
Calibrate the cameras (click "start wanding" in the Calibration Pane) and wave the calibration wand around the area. Aim for complete, uniform coverage. Click calculate when done and wait for a pop-up asking you to apply. The result should be "excellent" or better.
Set the ground plane by placing the calibration square at where you want (0,0,0) to be. The longer arm will become the -Y axis in ROS and the shorter arm will become the +X axis in ROS. Click "Set ground plane" in the Calibration Pane. Don't forget to do this, it will mess up your input to ROS and things will freak out. This is speaking from experience.
Attach mocap dots to the Crazyflie. Place it within the mocap area (easiest to put it at (0,0,0) and highlight all the dots in View Pane. Right click and select Rigid Body>Create From Select Markers. This will create a rigid body and list it in the "Assests" Pane.
In the Data Streaming Pane, select the correct network interface. Both computers (windows and the ROS machine) should have static IPs and be connected via ethernet. Set Stream Rigid Bodies to True. This will stream data from Motive to the ROS machine.
IMPORTANT: By default, the mocap_optitrack package only has has 2 rigid bodies defined. This can be changed in mocap_optitrack/config/mocap.yaml Copy the setup for Robot_1 or Robot_2 and add additional line for the number of robots you have. You should know which number cooresponds to which Crazyflie, as launching the mocap teleop nodes requires associating the correct number with the correct robot.