LogoLogo
WebsiteSupportDownloadsForumsQuick LinksContact Us
v2.3
v2.3
  • OptiTrack Support Documentation
  • WHAT'S NEW
    • Unreal Engine: OptiTrack InCamera VFX
  • QUICK START GUIDES
    • Quick Start Guide: Getting Started
    • Quick Start Guide: Precision Capture
    • Quick Start Guide: Tutorial Videos
    • Quick Start Guide: Prime Color Setup
    • Quick Start Guide: Active Marker Tracking
    • Quick Start Guide: Outdoor Tracking Setup
  • HARDWARE
    • Cameras
      • Ethernet Cameras
        • PrimeX 41
        • PrimeX 22
        • PrimeX 13
        • PrimeX 13W
        • SlimX 13
        • Prime Color
      • USB Cameras
        • Slim 3U
        • Flex 13
        • Flex 3
        • V120:Duo
        • V120:Trio
        • V120:Duo and Trio Setup
        • Adjusting Global Origin for Tracking Bars
    • Prepare Setup Area
    • Camera Mount Structures
    • Camera Placement
    • Camera Network Setup
    • Aiming and Focusing
    • Camera Status Indicators
  • MOTIVE
    • Installation and Activation
    • Motive Basics
    • Calibration
      • Continuous Calibration
      • Calibration Squares
    • Markers
    • Assets
      • Gizmo Tool: Translate, Rotate, and Scale
    • Rigid Body Tracking
      • Aligning Rigid Body Pivot Point with a Replicated 3D Model
    • Skeleton Tracking
    • Data Recording
      • Data Types
    • Labeling
    • Data Editing
    • Data Export
      • Data Export: BVH
      • Data Export: C3D
      • Data Export: CSV
      • Data Export: FBX
      • Data Export: TRC
    • Data Streaming
    • Camera Video Types
    • Audio Recording
    • Motive HotKeys
    • Measurement Probe Kit Guide
    • Motive Batch Processor
    • Reconstruction and 2D Mode
    • Tracking Bar Coordinate System
      • Transforming Coordinate System: Global to Local
  • MOTIVE UI PANES
    • Application Settings
      • Settings: Live Reconstruction
      • Settings: General
      • Settings: Views
      • Settings: Assets
        • Skeletons
        • Rigid Body
      • Settings: Camera
    • Mouse and Keyboard
    • Assets Pane
    • Builder Pane
    • Calibration Pane
    • Control Deck
    • Data Pane
    • Data Streaming Pane
    • Devices Pane
    • Edit Tools Pane
    • Graph View Pane
    • Info Pane
    • Labels Pane
    • Log Pane
    • Marker Sets Pane
      • Marker Name XML Files
    • Measurement Pane
    • Probe Pane
    • Properties Pane
      • Properties Pane: Camera
      • Properties Pane: Force Plates
      • Properties Pane: NI-DAQ
      • Properties Pane: OptiHub2
      • Properties Pane: Rigid Body
      • Properties Pane: Skeleton
      • Properties Pane: Take
      • Properties Pane: eSync2
    • Reference View pane
    • Status Panel
    • Toolbar/Command Bar
    • Viewport
  • PLUGINS
    • OptiTrack Unreal Engine Plugin
      • Unreal Engine: OptiTrack Live Link Plugin
      • Unreal Engine: OptiTrack Streaming Client Plugin
      • Unreal Engine: HMD Setup
      • Unreal Engine: MotionBuilder Workflow
      • Unreal Engine VCS Inputs
    • OptiTrack Unity Plugin
      • Unity: HMD Setup
    • OptiTrack OpenVR Driver
    • Autodesk Maya
      • Autodesk Maya: OptiTrack Insight VCS Plugin
    • Autodesk MotionBuilder
      • Autodesk MotionBuilder Plugin
      • Autodesk MotionBuilder: OptiTrack Skeleton Plugin
      • Autodesk MotionBuilder: OptiTrack Optical Plugin
      • Autodesk MotionBuilder: OptiTrack Insight VCS Plugin
      • Autodesk MotionBuilder: Timecode Data
    • OptiTrack Peripheral API
    • External Plugins
      • Houdini 19 Integration
  • ACTIVE COMPONENTS
    • Active Components Hardware
      • Active Puck
      • CinePuck
      • BaseStation
      • Information for Assembling the Active Tags
      • Manus Glove Setup
    • Configuration
      • Active Batch Programmer
      • Active Hardware Configuration: PuTTY
      • Active Component Firmware Compatibility
    • Active Marker Tracking
      • Active Finger Marker Set
      • Active Marker Tracking: IMU Setup
  • SYNCHRONIZATION
    • Synchronization Hardware
      • External Device Sync Guide: eSync 2
      • External Device Sync Guide: OptiHub2
    • Synchronization Setup
    • OptiTrack Timecode
  • VIRTUAL PRODUCTION
    • Unreal Engine: OptiTrack InCamera VFX
    • Entertainment Marker Sets
    • PrimeX 41
  • MOVEMENT SCIENCES
    • Movement Sciences Hardware
      • General Motive Force Plate Setup
      • AMTI Force Plate Setup
      • Bertec Force Plate Setup
      • Kistler Force Plate Setup
      • Delsys EMG Setup
      • NI-DAQ Setup
      • Multiple Device Setup
      • Prime Color Setup
    • Movement Sciences Marker Sets
      • Biomechanics Marker Sets
      • Biomech (57)
      • Rizzoli Marker Sets
    • For Visual3D Users
  • VIRTUAL REALITY
    • VR Plugins
      • VR Unreal Engine
        • OptiTrack Unreal Engine Plugin
        • Unreal Engine: OptiTrack Live Link Plugin
        • Unreal Engine: OptiTrack Streaming Client Plugin
        • Unreal Engine VCS Inputs
      • VR Unity
        • OptiTrack Unity Plugin
      • VR OpenVR
        • OptiTrack OpenVR Driver
    • VR HMD Setup
      • Unreal Engine: HMD Setup
      • Unity: HMD Setup
      • Manually Calibrating the HMD Pivot Point
      • Sync Configuration with an HTC Vive System
    • Navigation Controller Guide
    • SlimX 13
    • Active Marker Tracking
      • Active Finger Marker Set
      • Active Marker Tracking: IMU Setup
    • Synchronization Hardware
      • External Device Sync Guide: eSync 2
      • External Device Sync Guide: OptiHub2
  • ANIMATION
    • Autodesk Maya
      • Autodesk Maya: OptiTrack Insight VCS Plugin
    • Autodesk MotionBuilder
      • Autodesk MotionBuilder Plugin
      • Autodesk MotionBuilder: OptiTrack Skeleton Plugin
      • Autodesk MotionBuilder: OptiTrack Optical Plugin
      • Autodesk MotionBuilder: OptiTrack Insight VCS Plugin
      • Autodesk MotionBuilder: Timecode Data
  • ROBOTICS
    • PrimeX 22
    • Outdoor Tracking Setup
  • DEVELOPER TOOLS
    • Developer Tools Overview
    • NatNet SDK
      • NatNet 4.0
      • NatNet: Class/Function Reference
      • NatNet: Creating a Managed (C sharp) Client Application
      • NatNet: Creating a Native (C++) Client Application
      • NatNet: Data Types
      • NatNet: Matlab Wrapper
      • NatNet: Migration to NatNet 3.0 libraries
      • NatNet: RebroadcastMotiveData Sample
      • NatNet: Remote Requests/Commands
      • NatNet: Sample Projects
      • NatNet: Unicast Data Subscription Commands
      • Latency Measurements
    • Motive API
      • Motive API: Quick Start Guide
      • Motive API Overview
      • Motive API: Function Reference
      • Motive API Camera Calibration
    • Camera SDK
      • Camera SDK Classes
        • Class: cCameraGroupFilterSettings
        • Class: cCameraGroupMarkerSizeSettings
        • Class: cCameraGroupPointCloudSettings
        • Class: cCameraModule
        • Class: cRigidBodySettings
        • Class: cRigidBodySolutionTest
        • Class: cTTAPIListener
        • Class: cUID
  • MARKER SETS
    • Full Body
      • Baseline (37)
      • Baseline + Hinged Toe (41)
      • Baseline + Hinged Toe, with Headband (41)
      • Baseline + 13 Additional Markers (50)
      • Biomech (57)
      • Conventional (39)
    • Full Body + Fingers
      • Baseline + Hinged Toe + Fingers (49)
      • Baseline + 11 Additional Markers + Fingers (54)
      • Manus Glove Setup
    • Upper
      • Baseline Upper (25)
      • Baseline Upper Body + Fingers (33)
      • Conventional Upper (27)
    • Lower
      • Baseline Lower (20)
      • Helen Hayes Lower (19)
      • Conventional Lower (16)
    • Hand and Fingers
      • Left and Right Hand (11)
      • Active Finger Marker Set
    • Rizzoli Marker Sets
    • Entertainment Marker Sets
    • Rigid Body Skeleton Marker Set
  • GENERAL TROUBLESHOOTING
    • Troubleshooting
    • Running Motive on High DPI Displays
    • Firewall Settings
Powered by GitBook
On this page
  • Retroreflective Markers
  • Custom Markers
  • Active Markers
  • OptiTrack Active Markers
  • Custom Active Markers
  • Marker Placement
  • Marker Bases and Adhesives

Was this helpful?

Export as PDF
  1. MOTIVE

Markers

PreviousCalibration SquaresNextAssets

Last updated 2 years ago

Was this helpful?

OptiTrack motion capture systems can use both passive and active markers as indicators for 3D position and orientation. An appropriate marker setup is essential for both tracking the quality and reliability of captured data. All markers must be properly placed and must remain securely attached to surfaces throughout the capture. If any markers are taken off or moved, they will become unlabeled from the Marker Set and will stop contributing to the tracking of the attached object. In addition to marker placements, marker counts and specifications (sizes, circularity, and reflectivity) also influence the tracking quality. Passive (retroreflective) markers need to have well-maintained retroreflective surfaces in order to fully reflect the IR light back to the camera. Active (LED) markers must be properly configured and synchronized with the system.

Retroreflective Markers

OptiTrack cameras track any surfaces covered with retroreflective material, which is designed to reflect incoming light back to its source. IR light emitted from the camera is reflected by passive markers and detected by the camera’s sensor. Then, the captured reflections are used to calculate the 2D marker position, which is used by Motive to compute 3D position through reconstruction. Depending on which markers are used (size, shape, etc.) you may want to adjust the camera filter parameters from the Live Pipeline settings in .

Marker Size

The size of markers affects visibility. Larger markers stand out in the camera view and can be tracked at longer distances, but they are less suitable for tracking fine movements or small objects. In contrast, smaller markers are beneficial for precise tracking (e.g. facial tracking and microvolume tracking), but have difficulty being tracked at long distances or in restricted settings and are more likely to be occluded during capture. Choose appropriate marker sizes to optimize the tracking for different applications.

Circularity

If you wish to track non-spherical retroreflective surfaces, lower the Circularity value in in the application settings. This adjusts the circle filter threshold and non-circular reflections can also be considered as markers. However, keep in mind that this will lower the filtering threshold for extraneous reflections as well. If you wish to track non-spherical retroreflective surfaces, lower the Circularity value from the in the application settings.

Worn markers

Custom Markers


OptiTrack cameras can track any surface covered with retro-reflective material. For best results, markers should be completely spherical with a smooth and clean surface. Hemispherical or flat markers (e.g. retro-reflective tape on a flat surface) can be tracked effectively from straight on, but when viewed from an angle, they will produce a less accurate centroid calculation. Hence, non-spherical markers will have a less trackable range of motion when compared to tracking fully spherical markers.

Active Markers

OptiTrack Active Markers

Custom Active Markers

Active (LED) markers can also be tracked with OptiTrack cameras when properly configured. We recommend using OptiTrack’s Ultra Wide Angle 850nm LEDs for active LED tracking applications. If third-party LEDs are used, their illumination wavelength should be at 850nm for best results. Otherwise, light from the LED will be filtered by the band-pass filter.

  • Place a spherical diffuser around each LED marker to increase the illumination angle. This will improve the tracking since bare LED bulbs have limited illumination angles due to their narrow beamwidth. Even with wide-angle LEDs, the lighting coverage of bare LED bulbs will be insufficient for the cameras to track the markers at an angle.

  • Many applications that require active LEDs for tracking (e.g. very large setups with long distances from a camera to a marker) will also require active LEDs during calibration to ensure sufficient overlap in-camera samples during the wanding process. We recommend using OptiTrack’s Wireless Active LED Calibration Wand for best results in these types of applications. Please contact one of our Sales Engineers to order this calibration accessory.

Marker Placement

Asymmetry

Asymmetry is the key to avoiding the congruency for tracking multiple Marker Sets. When there are more than one similar marker arrangements in the volume, marker labels may be confused. Thus, it is beneficial to place segment makers — joint markers must always be placed on anatomical landmarks — in asymmetrical positions for similar Rigid Bodies and Skeletal segments. This provides a clear distinction between two similar arrangements. Furthermore, avoid placing markers in a symmetrical shape within the segment as well. For example, a perfect square marker arrangement will have ambiguous orientation and frequent mislabels may occur throughout the capture. Instead, follow the rule of thumb of placing the less critical markers in asymmetrical arrangements.

Marker Bases and Adhesives

All markers need to have a well-maintained retroreflective surface. Every marker must satisfy the brightness Threshold defined from the to be recognized in Motive. Worn markers with damaged retroreflective surfaces will appear to a dimmer image in the camera view, and the tracking may be limited.

Pixel Inspector: You can analyze the brightness of pixels in each camera view by using the pixel inspector, which can be enabled from the .

Please contact our to decide which markers will suit your needs.

OptiTrack's active solution provides advanced tracking of IR LED markers to accomplish the best tracking results. This allows each marker to be labeled individually. Please refer to the page for more information.

If your application requires tracking LEDs outside of the 850nm wavelength, the OptiTrack camera should not be equipped with the 850nm band-pass filter, as it will cut off any illumination above or below the 850nm wavelength. An alternative solution is to use the 700nm short-pass filter (for passing illumination in the visible spectrum) and the 800nm long-pass filter (for passing illumination in the IR spectrum). If the camera is not equipped with the filter, the Filter Switcher add-on is available for purchase at our . There are also other important considerations when incorporating active markers in Motive:

If an LED-based marker system will be strobed (to increase range, offset groups of LEDs, etc.), it is important to synchronize their strobes with the camera system. If you require a LED synchronization solution, please contact one of our to learn more about OptiTrack’s RF-based LED synchronizer.

Proper marker placement is vital for quality of motion capture data because each marker on a tracked subject is used as indicators for both position and orientation. When an asset (a Rigid Body or Skeleton) is created in Motive, its unique spatial relationships of the markers are calibrated and recorded. Then, the recorded information is used to recognize the markers in the corresponding asset during the process. For best tracking results, when multiple subjects with a similar shape are involved in the capture, it is necessary to offset their marker placements to introduce the asymmetry and avoid the congruency.

Read more about marker placements from the page and the page.

Prepare the markers and attach them on the subject, a Rigid Body or a person. Minimize extraneous reflections by covering shiny surfaces with non-reflective tapes. Then, securely attach the markers to the subject using enough adhesives suitable for the surface. There are various types of adhesives and marker bases available on our for attaching the marker: Acrylic, Rubber, Skin adhesive, and Velcro. Multiple types of marker bases are also available: carbon fiber filled bases, Velcro bases, and snap-on plastic bases.

camera properties
Application Settings
Sales team
Active Marker Tracking
webstore
Sales Engineers
auto-labeling
Rigid Body Tracking
Skeleton Tracking
webstore
Application Settings
2D object filter
cameras tab
2D reflections filtered by the Size and Roundness (circularity) filter
Ultra Wide Angle 850 nm LEDs