Motion Controllers

Note: This article is under construction and will be published in a few days. Meanwhile refer to v2 documentation:

• User Guide
• Using for Head Tracking

iPi Motion Capture allows to use motion controllers in addition to cameras for improved tracking of smaller details.

• Wrist rotations can be tracked only with motion controllers due to low resolution of video.
• Though head can be tracked with camera, using a motion controller for that purpose greatly reduces the processing time and may provide better accuracy.

Essentially, a motion controller provides 3D orientation value which can be used to track rotations of a single bone it is attached to.

Equipment

PlayStation Move

Wii Remote with MotionPlus

Wii Remote Plus

iPi Recorder supports these models of motion controllers:

• PlayStation Move
• Wii Remote with MotionPlus
• Wii Remote Plus, which has MotionPlus integrated

Your PC should be equipped with a Bluetooth radio module to connect with motion controllers. If you do not have a built-in one, you'll need an USB Bluetooth adapter.

iPi Recorder does not limit the number of connected motion controllers. However, the hardware does. Usually, a single Bluetooth adapter can handle up to 4 PS Move controllers. This is sufficient for a single actor, but for multiple actors you may need more controllers. Thus, additional Bluetooth adapter(s) is required. Unfortunately, standard Windows Bluetooth drivers do not support multiple adapters. To use multiple Bluetooth adapters, it is necessary to install Motion in Joy drivers.

For PS Move, an USB to mini-USB cable is also required to charge your motion controller and for pairing (see next section).

Tip: Unless you already have Wii stuff, we strongly recommend to use PlayStation Move, because of its built-in magnetometer. In short, the presence of magnetometer gives a lot more stable orientation value. Without it, orientation tends to drift around vertical axis, and this leads to less accurate measurements.

Recording

To get your motion controller in the list of devices, it must be connected to a PC via Bluetooth. But before it can connect to your Bluetooth adapter, the controller must be paired with it. For that, press the Add Controller button in the toolbar, select device type you have, and then follow the instructions specific for this device.

For PS Move, pairing is one-time process unless you reconnect motion controller to another PC or gaming console. Each time you connect controller to another host, it should be paired. After pairing, the Bluetooth connection is established automatically each time you power on the motion controller. To power on PS Move, press the PS button. To power off, hold down the PS button for a long time (about 10 seconds).

For Wii Remote, pairing should be done each time after Bluetooth connection is lost, powering off either the motion controller or the PC. This is another disadvantage of Wii Remote. To power off Wii Remote, hold down the Power button for a couple of seconds.

Note: On Windows 8.x, PS Move does not work properly using the standard Bluetooth drivers included with the OS. For these OS versions, it is recommended to install Motion in Joy drivers.

Note: The recent revisions of Wii Remote Plus controllers may not work properly using the standard Bluetooth drivers. For them, you can use Toshiba Bluetooth stack.

After you have successfully paired the controllers with Bluetooth adapter, they should be visible in device list. Select them in addition to cameras and press the Record Video button. Motion controller is visualized as a rotating blue "brick" showing its orientation in space. Hover mouse on the controller's screen and you'll see some useful controls like battery indicator and view selection.

When controller is being used for the first time (or have not been used for a long period) a message is displayed over it saying it is not calibrated. Calibration of a motion controller (not confuse with calibration of cameras) is needed for more accurate measurements, so it is highly recommended to get through it every time you see this message. To run calibration process, just click on the message or press the CALIBRATE button in the on-screen controls.

After a motion controller is calibrated, you can use it in recording action videos.

Tip: You can use motion controller to start/stop recording (including background evaluation). Just hold PS Move's Start button, or Wiimote's A button for a few seconds, until you feel a vibration.

Tip: Generally, there is no need to enable motion controllers when recording calibration videos, because their data will not be used in the calibration process. However, you can use PS Move's light sphere as a light marker for calibration.
You can light it with different colors using on-screen controls for PS Move or by pressing corresponding buttons on PS Move itself. Buttons work even if PS Move is not selected for recording. White color usually works best for the calibration.
It is not recommended to light PS Move when recording action videos as it can lead to more tracking errors.

Tips on action video

Aiming at a camera

Standard grip

There are two main requirements:

1. At some moment during the record (for example, at the beginning), you should aim with (each) motion controller at one of the cameras. This is needed to correctly orient the motion controller within the scene coordinate space in iPi Mocap Studio.
2. For correct orientation of prop models in iPi Mocap Studio, hold the controller as if its side with buttons is a back side of a prop in a "standard" position — i.e. facing the actor's face when the arm with prop is stretched forward. Of course, you can use a non-"standard" grip of the controller if such a grip for a prop is implied by the scenario of the action.

Now, the tips:

• If you have already made some records without explicitly aiming at the camera, these videos may not be going to trash. Look thoroughly through all the frames — it is very likely that at some point the actor aimed at some camera by accident, at least in horizontal direction (this is sufficient).
• You can use special accessories for motion controllers like shooting attachments. In that case, the relative position of the controller to the prop is good known, so you just hold it as needed by the scenario (i.e. the requirement #2 is not relevant for this case).
• You can change the grip of the motion controller during the action. The iPi Mocap Studio allows you to process every frame range with the same grip independently.