In an optical motion capture system, multiple synchronized cameras are installed around the target capture volume, and 2D images are captured from each camera. 2D positions are calculated, and the overlapping position data are compared to compute the 3D positions via triangulation.
Optical motion capture systems obtain the data through detecting emitted or reflected light. Therefore, it is recommended to minimize the ambient lighting to reduce interferences, which includes sunlight and extraneous illumination or reflection sources.
The ideal camera placement may vary depending on the capture application. Generally, it is beneficial to have cameras arranged around the periphery of the volume at varying heights so that each camera captures a distinct view of the volume.
Take a look at the volume layouts located on the Build Your Own page for additional guidance about placing your cameras.
The Primex 41 is capable of tracking a 16 mm mocap marker from a distance of 100 feet.
Note that the trackable range in optical motion capture depends on many variables, mostly on the marker size, the marker type, and the capture environment settings. Our Primex series cameras are equipped with a powerful LED illumination array and a high resolution imager which allows tracking at very long distances.
OptiTrack camera systems have the fidelity to capture all types of human body and rigid body movements, including both subtle and fast motions. Rigid body movement can be captured when at least three markers are visible. Facial movement and skeletons can be tracked as long as a sufficient number of markers are visible. Movements that involve excessive occlusion of markers may require adjustment to the marker set and camera placement. More dynamic motions will benefit from a larger capture volume to work within.
Yes, props and skeletons can be captured at the same time.
With an optimized capture setup and an Unlimited license, an OptiTrack system can track up to 12 actors with props. It is important to note that with a basic license its only 3 skeletons, however, this is a license limitation not a software limitation.
Note that the number of people or objects that can be tracked with an optical motion capture system is based on multiple influencing factors, which include the capture environment and the system setup specification. Depending on how these factors are optimized, the maximum number of trackable assets may vary substantially. For this reason, it is difficult to state a maximum number. The Build Your Own feature on our website will provide some guidelines which are recommended minimums for the system setup and number of actors that can be tracked.
If you wish to track higher numbers of rigid bodies or people than the number indicated in Build Your Own, consult one of our Sales Engineers to find out which system setup is appropriate for a particular application.
Related Page: Skeleton Tracking
With an optimized capture setup, an OptiTrack system can track 84 rigid bodies at a time, however, this number is not exhaustive. This is just how many rigid bodies we were able to test at one time. This number is potentially higher.
Note that the number of people or objects that can be tracked with an optical motion capture system is based on multiple influencing factors, which include the capture environment and the system setup specification. Depending on how these factors are optimized, the maximum number of trackable assets may vary substantially. For this reason, it is difficult to state a maximum number. The Build Your Own feature on our website will provide some guidelines which are recommended minimums for the system setup and number of actors that can be tracked.
If you wish to track higher number of rigid bodies or people than the number indicated in Build Your Own, consult one of our Sales Engineers to find out which system setup is appropriate for a particular application.
Related Page: Rigid Body Tracking
Yes, outdoor tracking is possible with OptiTrack camera systems. Our Prime series cameras feature high-powered LED strobes which are suited for detection of passive (reflective) markers in strong sunlight. To further improve marker visibility and tracking range, active (LED) markers can be used in place of passive markers.
Related Page: Outdoor Tracking
With a Motive Body license, there are standard marker sets that create a skeletal model which target both finger and body movements. Here, the finger tracking is done by analyzing the kinematics of the hand and estimating the pose of each finger. For accurate finger tracking performance, markers can be attached directly to the fingers using skin adhesives. A full line of adhesive markers are available in our webstore. Motive is also compatible with Manus, a third-party producer of motion trackable gloves. For more information, please visit the Manus website.
Related Page: Manus Glove Setup
Yes, performance capture is supported with a Motive Body license. OptiTrack cameras enable users to capture fine details from facial expressions while simultaneously tracking the body motion.
The 3D location of markers can be resolved with sub-millimeter accuracy with an optimal capture volume size and camera configuration.
When connected to the OptiHub2 or the eSync2, cameras can synchronize their exposure timing to external sources. Common uses are to synchronize capture data with software or hardware controls such as force plates, shutter glasses, timecode generators, or head mounted displays.
Related Pages: External Device Setup OptiHub2, External Device Setup eSync2
Yes, our motion capture cameras are capable of frame rates up to 360 Hz, making non-smeared motion tracking for most objects possible. For example, we regularly track swinging golf clubs which travel up to 125 mph.
For most applications, 3D data is processed in real-time at the full system frame rate. For data intensive applications, the system processes the 3D data in real-time as quickly as possible, resulting in live 3D data on most but not all frames.
For all applications, recorded data can be processed for all captured frames regardless of the frame rate.
Yes, all OptiTrack cameras have the capability of transmitting the entire grayscale frame to the host PC. Motive or the Camera SDK provides the ability to select the video mode and access the data. Furthermore, MJPEG grayscale video is also supported for transmitting downsampled images in order to reduce network traffic.
Raw grayscale and MJPEG video modes are useful for recording reference videos and adjusting focus and aiming of the camera.
Raw grayscale video mode from the camera allows transmitting a full resolution grayscale image. Raw grayscale images consume large amounts of network bandwidth. For this reason, raw grayscale video mode is more useful for focus and aiming of cameras.
For reference video applications, MJPEG grayscale mode transmits compressed images which reduces the bandwidth for recording video. This guarantees that video will be captured at the full camera frame rate under most conditions.
The IR intensity setting is now an on/off setting. Please adjust the exposure setting to adjust the brightness of the image in the IR spectrum.
The Exposure value in the camera setting controls how long the shutter remains open, per frame. Increasing the Exposure value allows more light in, creating a brighter image that can increase visibility for small and dim markers. However, setting the Exposure too high can introduce merging of adjacent markers and marker blurring—all of which can negatively impact the tracking quality.
The Threshold setting determines a minimum brightness of a pixel for it to be considered in the calculation of a 2D object. All pixels with a brightness below the Threshold setting are ignored.
Increasing the Threshold value can help filter light interference from non-markers in the camera view. Lowering the Threshold value can allow less-visible markers (e.g. small markers, worn markers, and markers at longer distances from the camera) to be seen by the camera.
The Frame Rate (FPS) value determines the number of images a camera will capture per second. A higher FPS value will record more data within a given time. A lower FPS value will allow for higher exposure values for brighter images and will also reduce network traffic.
The maximum frame rate of the system will be limited to that of the camera with the lowest maximum frame rate.
Increasing the Gain setting amplifies the brightness of the entire image and it can be used to improve the tracking at very long distances. Specifically, changing the Gain setting applies a multiplier to the brightness of every pixel in the image before applying the Threshold setting.
Related Page: Properties Pane: Camera
OptiTrack cameras use Motive to collect and process motion capture data. There are two license types of Motive capable of capturing data from the camera system: Motive:Tracker and Motive:Body.
Motive:Tracker is capable of tracking rigid bodies. Motive:Body supports both skeletal tracking and rigid body tracking.
Motive:Edit is available for editing and playback purposes only.
Related Page: Installation and Activation
Yes, Motive:Body supports real-time processing with skeleton solving. This includes the ability to stream live skeleton data to other software in real-time using a variety of streaming protocols.
Motive distinguishes different objects and people by recognizing the uniqueness of the marker arrangement. When an asset is created, the spatial relationships between markers are recorded and used to recognize and differentiate multiple people or objects. When two or more objects or people are about the same size and shape, it is beneficial to offset one or more markers (e.g. waist markers) so Motive can differentiate between them. Skeleton markersets in Motive have optional magenta markers. These markers are in addition to the required white markers and can be placed uniquely to differentiate two actors/skeletons from each other.
Related Page: Marker Sets
Motive supports highly optimized skeleton templates for various applications. Moreover, edit options for adding and removing extra markers to or from the template skeleton are available, which allows partial customization of marker sets.
Related Page: Skeleton Tracking
Motive:Tracker supports exporting tracking data in CSV and C3D format. Motive:Body supports exporting CSV and C3D file format. It also exports FBX (Binary and ASCII), BVH, and TRC. Furthermore, the capture data can also be streamed to other software utilizing supported plugins and data-streaming pipelines.
Related Page: Date Export
Motive will run on Windows 8.1 or later. MacOS is not currently supported. Ubuntu and Fedora distros are able run NatNet and have the ability to receive streaming data from a Windows machine running Motive.
Related Page: Installation and Activation
The Camera SDK provides access to the most fundamental data, such as grayscale images and 2D object information, from each camera. Available data includes the sub-pixel weighed center (X, Y) position and area of the marker on the imager in pixels.
Motive reconstructs 3D points from 2D data collected from each camera, and both the 3D position and orientation for skeletons and rigid bodies can be calculated.
Motive:Tracker provides access to the rigid body data. Motive:Body provides access to both skeletal data and rigid body data.
Related Page: Data Export
The information available for markers in the Camera SDK is the sub-pixel weighed center X, Y position and area of the marker on the imager in pixels.
In Motive, reconstructed 3D data with X, Y, Z coordinate information, along with rotation X, Y, and Z information, is available.
Related Page: Reconstruction and 2D Mode
NatNet does not support streaming over the Internet. A direct ethernet cable connection or private LAN/hub for the client and server are the preferred configurations. Streaming over local LANs is also supported by NatNet, however that setup may generate unwanted traffic for other users on the network.
The Motive Batch Processor is a stand-alone application built on the NMotive scripting and programming API. It allows scripted access to file input and output, reconstruction and auto-labeling, high-level processing using many of Motive's existing editing tools, and data export. The Motive Batch Processor is designed to utilize user-authored scripts for custom applications.
Sample script files and a class reference file for the Motive Batch Processor can be found in the Motive folder.
Sample script files: [MotiveInstallDirectory]\MotiveBatchProcessor\ExampleScripts
Class reference file: [MotiveInstallDirectory]\Help
Related Page: Motive Batch Processor
Motive provides FBX/BVH/C3D file export, which is compatible with many common 3D rendering and animation packages (i.e. Maya, 3D Studio Max, MotionBuilder). Real-time streaming plugins are also available for MotionBuilder and 3D Studio Max. 3D streaming protocols are also supported for other applications: Trackd, VRPN, and the OptiTrack NatNet protocol.
The NatNet SDK is a client/server networking SDK designed for sending and receiving motion capture data across networks. Customers who wish to write their own plugins or applications can make the motion capture data available to other applications in real-time. It utilizes UDP along with either Unicast or Multicast communication for integrating and streaming reconstructed 3D data, rigid body data, and skeleton data from OptiTrack systems.
Related Page: Autodesk MotionBuilder Plugin
Yes, recorded reference videos can be exported into AVI video files. Note that these files may not be playable on Windows Media Player. Use a robust media player (i.e. VLC) for playing back exported video files.
Yes, audio files can be exported into WAV audio files. Note that these files may not be playable on Windows Media Player. Use a robust media player (i.e. VLC) for playing back exported audio files.
Related Page: Audio Recording
There are three OptiTrack development APIs that are useful for developing a custom application: the Camera SDK, the NatNet SDK, and the Motive API. All of the APIs support a C/C++ interface.
The Camera SDK provides access to the most fundamental data, such as grayscale images and 2D object information, from each camera. In addition, the Motive API also allows control of and access to the backend software platform of Motive. Not only does it allow access to 2D camera images and the object data, but it also gives control over the 3D data processing pipeline.
The NatNet SDK is a client/server networking SDK designed for sending and receiving motion capture data across networks. The NatNet SDK makes the motion capture data available to other applications in real-time. It utilizes UDP along with either Unicast or Multicast communication for integrating and streaming reconstructed 3D data, rigid body data, and skeleton data from OptiTrack systems.
Related Pages: Motive API: Quick Start Guide, Camera SDK, NatNet SDK
Camera SDK is free software available for download from the OptiTrack website.
Motive provides advanced 3D and 6DoF tracking capabilities and may be purchased separately.
Yes, the Camera SDK supports multi-camera synchronization with all OptiTrack cameras. In fact, all OptiTrack cameras are synchronized at the hardware level. But note that using synchronized cameras to reconstruct markers into a 3D space cannot be done through the Camera 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 allows the user to read through the license which accompanies them. Most installer engines have the ability to invoke another installer during the installation process.
If you have a special distribution request, please contact us to discuss it in detail.
The preferred approach is to link to the Camera SDK installer hosted on the NaturalPoint web servers. However, if you would like to bundle our installer with your application, a formal endorsement is necessary.
In order to get a formal endorsement, please contact support@naturalpoint.com and provide contact information and detailed information about your project.