Freqently Asked Questions

1. ACCESSORIES:

1. Imager and Lens specifications and use - Default Lens and Wide FOV (Field Of View) Lens
2. Raw Material - What is this? Is this used to place markers in a scene?
3. SmartNav Hat - Is this just a normal hat?
4. It appears that you only supply smaller tripods. Is this an operational requirement or can taller higher tripods be used?
5. Do you sell active (LED) wireless markers?

2. SPECIFICATIONS:

1. How delicate are the FLEX:3 and SLIM:V100 cameras? It appears they are attached to a green board without any case?
2. Cabling - Can the USB cabling be used in conjunction with a Ethernet network via an USB Ethernet adapter, or would this degrade the quality of the data?
3. Is it possible to maintain the full frame rate when using multiple cameras?
4. Is it possible to get greyscale video out of the camera?
5. What frame rates and image sizes work for grayscale video mode?
6. At what frame rate can the images (if so desired) from the cameras be read?
7. Do the OptiTrack cameras work with active (LED) and passive (retroreflective) markers?
8. What is the field of view of the cameras?
9. Is the OptiTrack SDK included with the purchase of the OptiTrack hardware?
10. What is the pinout for the SLIM:V100 I2C, SYNC, LED header?

3. COMPATABILITY AND DATA FORMATS:

1. Are Linux drivers available?
2. What marker data formats are available?
3. What coordinate formats are available for the marker position data?
4. What other FEM-CAD and Graphic applications (e.g. Matlab, Amira, 3D Studio Max, Ideas, Abacus, etc.) are compatible with the OptiTrack?

4. TRACKING CAPABILITY:

1. What is the maximum distance that markers can be tracked by OptiTrack cameras?
2. How does the software cope with occlusion?
3. What is the recommended operating environment for using OptiTrack cameras?
4. How many 'objects' (i.e. markers) is the OptiTrack system capable of detecting?
5. Is there any extra processing that occurs when using multiple cameras?
6. When a new frame is acquired on a camera, what information is sent over the bus (e.g. just a notification, the entire image, just dot positions, etc.)?
7. How is the synchronization of multiple cameras handled?
8. How does the Vector feature select the objects to use for its calculation?
9. Does the OptiTrack SDK track objects and extract coordinate information from multiple cameras?
10. Is it possible to control the camera illumination?
11. Is the coordinate acquisition in real time or the processing is done after the acquisition of the movement?
12. What angles and distances are in the vector calculation and tracking?
13. Is OptiTrack good for motion capture like character animation, 3D modeling, dance, animated movies or games?

5. SDK INSTALLER USAGE & DISTRIBUTION:

1. Can OptiTrack runtime/components be repackaged into installers and distributed with applications based on the OptiTrack SDK?

6. TRACKING TOOLKITS (POINT CLOUD & RIGID BODY):

1. Is there sorting and tracking of 3D points?
2. Can the baseline OptiTrack API be used in the same application as the Point Cloud API?
3. What output formats are available for the Rigid Body toolkit?

ARENA MOTION CAPTURE SOFTWARE:

• Read the Motion Capture FAQ
  
  

SOFTWARE LICENSING & ACTIVATION:

• Read the Licensing & Activation FAQ
  
  

1. Accessories

1-01. Imager and Lens specifications and use - Default Lens and Wide FOV (Field Of View) Lens

The lens that comes with the camera is exactly matched to the IR illumination ring that also comes with the camera. If you are going to use passive markers or little reflective balls, then stick with the standard lens. The default lens has an Effective Focal Length of 3.4mm.

If you are planning on using active markers, IR LEDs, then the wider FOV lens could be of use. The FOV is 57 degrees horizontal and the focal length of the wide angle lens is 2.1mm. See the Lens Comparison Table for FOV information specific to each camera and lens combination.

The FLEX:C120 imager specifications from the manufacturer are 352x288 pixels, 1/7" 2.2mm x 1.8mm with a square pixel pitch of 6 micron. The functional image that is sent from the camera is slightly larger (355x288) than the area specified in the imager data sheet, the SDK returns the larger image area to reflect the additional available pixels.

For the V100 cameras, the pixel size is 6 microns square, the imager size is 4.5mm x 2.88mm, and the active pixel area is 752x480 (but is windowed to 640x480).

1-02. Raw Material - What is this? Is this used to place markers in a scene?

This is a 1 inch wide, foot long strip of 3M reflective tape, with sticky fiber backing instead of the cheap sticker backing.

Purchase several feet of raw material and either place it directly as a marker, or wrap it around small balls, typically wood or plastic ones from a craft store, to make round reflective markers.

Spherical reflective markers can also be purchased from the OptiTrack online store.

1-03. SmartNav Hat - Is this just a normal hat?

No. This is a normal baseball cap that has reflective material incorporated into the center of brim, and sewn into the rear adjustment strap. For more information, see the SmartNav accessories page.

1-04. It appears that you only supply smaller tripods. Is this an operational requirement or can taller higher tripods be used?

We actually do have some larger tripods for sale. I would recommend one of our lighting stands instead of a tripod, they are much cheaper and extend up to 10ft. They also require a ball head adapter. Feel free to use your own tripods, anything should work, just make sure that you have them on a very stable surface, like concrete, so there is no vibration transferred from the floor to the camera, causing it to move.

1-05. Do you sell active (LED) wireless markers?

The only markers we currently provide are passive retro-reflective markers which are illuminated by the camera-mounted LEDs. It is also possible to use infrared LEDs powered by a battery (active markers) with the OptiTrack cameras. In our online store, we sell IR LEDs which can be used in the creation of active markers.

2. Specifications

2-01. How delicate are the FLEX:3 and SLIM:V100 cameras? It appears they are attached to a green board without any case?

The FLEX:3 camera board is attached directly to a plastic mounting base that can then be mounted on a tripod. The SLIM:V100 camera board has an optional enclosure which can be purchased from the OptiTrack online store. Both cameras are very robust.

2-02. Cabling - Can the USB cabling be used in conjunction with a Ethernet network via an USB Ethernet adapter, or would this degrade the quality of the data?

This could work, but we have not tried it. Typically, a user will put a few cameras together, say up to 4, connect them with a USB hub and then run the single hub cable to the computer. USB cables run only 5 meters(M), so you will need repeating extension cables if you have the hub more than 5M away, but we do not sell them directly.

2-03. Is it possible to maintain the full frame rate when using multiple cameras?

Yes, the cameras maintain the full frame rate with multiple cameras arrayed.

2-04. Is it possible to get greyscale video out of the camera?

Yes, the FLEX:V100 and FLEX:C120 cameras have the capability of transmitting the entire greyscale frame to the PC. The OptiTrack SDK provides the ability to select this video mode and access the data.

The FLEX:3 cameras only transmit 1 bit monochrome thresholded video; this means anything below the threshold is off and anything above it is on. The individual bright objects in the video frame get color coded based on their rank among the other tracked objects; the color is then superimposed over the video stream. The color information is not part of the actual video stream.

2-05. What frame rates and image sizes work for grayscale video mode?

FLEX:V100 & SLIM:V100: It is only possible to get 640 x 480 grayscale at 100 FPS exposure rate with 50% frame decimation under some conditions. To achieve that, it is usually necessary to have only a single camera connected to your system's USB port and have no additional USB hubs plugged into the system. The down-sampled modes work under more diverse system configurations. They provide 320 x 240 and 160 x 120 grayscale at 100 FPS exposure with no frame decimation under most conditions.

FLEX:C120: It is usually possible to get 355 x 288 grayscale at 120 FPS. Under heavier USB load with additional cameras it may be necessary to set the Frame decimation mode to 50% or greater.

Additionally, using the windowing feature to reduce the horizontal size of the image can improve the ability to transfer grayscale video. Some USB chipsets provide greater grayscale throughput than others.

2-06. At what frame rate can the images (if so desired) from the cameras be read?

The 1 bit thresholded image and/or tracked marker coordinate data can be extracted in real time at the full frame rate from each camera. If you wish to sample at a slower rate, you may discard data.

2-07. Do the OptiTrack cameras work with active (LED) and passive (retroreflective) markers?

The cameras are compatible with both active and passive markers. Active markers work best when using LEDs that produce output in the 850nm wavelength.

2-08. What is the field of view of the cameras?

The field of view for the default lens can be found on the specifications page for each camera: FLEX:V100, SLIM:V100, FLEX:C120. It is possible to use different lenses to change the field of view. See the Lens Comparison Table for FOV information specific to each camera and lens combination.

2-09. Is the OptiTrack SDK included with the purchase of the OptiTrack hardware?

The OptiTrack SDK license is included when you purchase the cameras, there is no additional charge. You can also download the SDK from our website to review it before purchasing. The SDK provides an API for interfacing with the OptiTrack cameras and the tracking data which they produce.

The add-on Point Cloud and Rigid Body toolkits provide advanced tracking capabilities and are available at an additional cost.

2-10. What is the pinout for the SLIM:V100 I2C, SYNC, LED header?

Pin-out settings for SLIM:V100 8-pin header is:

1, GND
2, 5V
3, 3.3V
4, I2C SCL
5, I2C SDA
6, LED OUT  (this is the one you want)
7, SYNC OUT
8, SYNC IN

Pin 1 is the square one at the bottom of the board.

Be careful to draw no more than 50ma from the 3.3V supply, if you choose to tap that.

3. Compatability and Data Formats

3-01. Are Linux drivers available?

We do not have any new information about the availability of Linux support at the moment, though we will share that information with our users if any becomes available.

3-02. What marker data formats are available?

The baseline OptiTrack SDK only provides marker data as a real-time stream of 3D imager coordinates. If you wish to record the data, you will need to write your own application.

The Point Cloud toolkit provides a real-time stream of 3D marker coordinates and the option to record to CSV files.

NaturalPoint's forthcoming Full Body Motion Capture software will provide real-time 3D marker and skeleton data, along with BVH file output.

3-03. What coordinate formats are available for the marker position data?

The information available for markers in the baseline OptiTrack SDK is the sub-pixel weighted center X, Y position and area of the marker on the imager in pixels.

If you use the Vector Tracking component of the API, it will provide X, Y, Z, Roll, Pitch and Yaw, as well as the X, Y, Z position for a cluster of 3 markers in a known configuration.*

Marker data in 3D physical coordinates is available when using the Point Cloud toolkit.

* Not officially supported.

3-04. What other FEM-CAD and Graphic applications (e.g. Matlab, Amira, 3D Studio Max, Ideas, Abacus, etc.) are compatible with the OptiTrack?

There is no direct support in the baseline OptiTrack SDK for communication with these types of applications. It would be necessary to use our SDK and the SDK for these applications to write software which would connect them.

NaturalPoint's forthcoming Full Body Motion Capture software will provide BVH file output which can be used in many applications, as well as real-time streaming to MotionBuilder.

4. Tracking Capability

4-01. What is the maximum distance that markers can be tracked by OptiTrack cameras?

The range depends upon the size of the marker, camera model, and lens used. Please check the Camera Comparison Table for more details. Typically, larger markers and smaller FOV lenses allow for greater tracking range.

4-02. How does the software cope with occlusion?

The baseline OptiTrack SDK does not provide any special handling of occlusion. It is a development platform on which customers can build their own applications that implement multi-camera tracking and handle occlusion.

For customers who wish to purchase this capability, the Point Cloud toolkit does provide a ready-to-use tracking solution that utilizes multiple cameras to handle occlusion. As long as a marker is visible to at least two cameras, the Point Cloud toolkit will attempt to track it. More cameras can be added to provide better coverage and reduce occlusion.

4-03. What is the recommended operating environment for using OptiTrack cameras?

The ideal environment would have no external sunlight and only using fluorescent light. This should prevent false objects.

4-04. How many 'objects' (i.e. markers) is the OptiTrack system capable of detecting?

The number of markers that the OptiTrack is capable of tracking depends on the size of the markers and the distance they are from the camera. At a distance of four feet, the FLEX:C120 can track at least 40 half-inch markers and the V100 cameras can track at least 80 half-inch markers.

4-05. Is there any extra processing that occurs when using multiple cameras?

If the 2D marker data from multiple cameras does not need to be combined, then the baseline OptiTrack SDK does not require any additional processing. If multi-camera 3D tracking in required, then the Point Cloud toolkit should be used. The Point Cloud toolkit handles all additional processing required to track and combine the marker data.

4-06. When a new frame is acquired on a camera, what information is sent over the bus (e.g. just a notification, the entire image, just dot positions, etc.)?

In Greyscale Mode (FLEX:C120, V100 models), all of the pixel data including intensity information is sent to the PC over the USB bus. In Preprocessed Mode (C120, V100), a 1 bit thresholded image is transferred to the PC where the final marker positions are calculated. In Preprocessed Object Mode (V100 only), all of the calculations are done in the camera and only the final marker positions are sent to the PC.

4-07. How is the synchronization of multiple cameras handled?

The FLEX:C120 and FLEX:V100 cameras provide hardware-based synchronization; this allows them to expose frames at the exact same time. In order to take advantage of synchronization, the cameras must be connected to each other using Sync Cables (sold separately from cameras).

4-08. How does the Vector feature select the objects to use for its calculation?

The Vector feature uses it's own tracking algorithm to identify which objects should be used for the calculation, and does not necessarily use the top three ranked objects from the general tracking results. The vector calculations assume that you are only tracking a vector clip* with minimal noise in the background. It uses the size and positions of the 3 largest markers to find the points.

* Not officially supported.

4-09. Does the OptiTrack SDK track objects and extract coordinate information from multiple cameras?

The baseline OptiTrack SDK addresses multiple cameras individually but does not correlate the tracking information between them. It does not extract the common 3DOF coordinate position for objects which are visible to multiple cameras at the same time, it only provides imager-pixel coordinates for each object per-camera.

If multi-camera 3D tracking in required, then the Point Cloud toolkit should be used. The Point Cloud toolkit handles all additional processing required to track and combine the marker data.

4-10. Is it possible to control the camera illumination?

The FLEX:C120 and FLEX:V100 models have the ability to adjust the intensity of their built-in IR LED rings. The FLEX:V100 also has a strobed illumination mode which provides a short burst of illumination at the start of the frame. There is no support for synchronizing external illumination sources with the frame exposure of the OptiTrack cameras in the current hardware.

4-11. Is the coordinate acquisition in real time or the processing is done after the acquisition of the movement?

The acquisition and processing all occurs in real time. It is possible to use our SDK to access the data if you wish to write an application to record it for post-processing.

4-12. What angles and distances are in the vector calculation and tracking?

The X, Y, and Z values are distances in mm from the camera. The point used to calculate this position is a rough estimate of the point of rotation of a person's head. The position is calculated assuming the vector clip* is placed on the brim of a baseball cap on the user's head. It is calculated by taking a normal to the plane formed by the vector clip. Human head rotation is a complex movement, so this point of rotation is a simplification of the problem.

The angles returned by the API are simply the angles formed by the vector plane. Typically they are used as relative measures where the users "center" themselves to the camera.

The algorithm for determining the position of the vector clip is proprietary.

* Not officially supported.

4-13. Is OptiTrack good for motion capture like character animation, 3D modeling, dance, animated movies or games?

The baseline OptiTrack SDK only provides basic 2D tracking; it does not include support for 3D motion capture or tracking. NaturalPoint's forthcoming Motion Capture software will be a complete full body solution with BVH file output and real-time streaming of 3D marker and skeleton data to MotionBuilder.

5. SDK Installer Usage & Distribution

5-01. Can OptiTrack runtime/components be repackaged into installers and distributed with applications based on the OptiTrack SDK?

We request that OptiTrack runtime/components be delivered using the installers we provide; they should not be repackaged. This helps ensure that everything is installed properly and also gives the user has a chance to view the license which accompanies them. Most installer engines have the ability to invoke another installer (such as the OptiTrack SDK one) during the installation process.

If you have a special distribution need, you can contact us via our contact form to discuss it in detail.

6. Tracking Toolkits (Point Cloud & Rigid Body)

6-01. Is there sorting and tracking of 3D points?

The Point Cloud toolkit does not provide tracking of points between consecutive frames, it will only return information about the markers found in the current frame. There is also no guarantee markers will be delivered in the same order from one frame to the next (no sorting).

6-02. Can the baseline OptiTrack API be used in the same application as the Point Cloud API?

Currently, it is not possible to access the cameras through baseline OptiTrack API once you've initialized and are using the Point Cloud SDK. We are looking in to providing either concurrent use of both libraries or making some of the baseline functionality available through the Point Cloud toolkit.

6-03. What output formats are available for the Rigid Body toolkit?

The Rigid Body toolkit includes an API which applications can use to capture real-time data. The Rigid Body GUI tool can be used to record and save data captures to disk.

There are also three real-time network streaming formats available:

• TrackD support (Mechdyne's proprietary 6DOF data protocol)
• VRPN support (open source 6DOF data protocol)
• NatNet format (open source generic 6DOF data protocol from NaturalPoint)
  
  

Please let us know if you have a question that is not addressed here, by emailing us via our contact form.