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Theia Axiom - v2025
Theia Axiom - v2025
  • Theia3D Documentation
    • What's New
    • Theia3D Documentation
    • Welcome to Theia3D
    • Keyboard Shortcuts
    • Getting Started
      • System Requirements
      • Installation
      • License Activation
      • Startup Window
      • Theia3D Basics
      • Camera Setup Tips
      • Tutorial Videos
    • Data Collection
      • Data Collection Principles
      • Recording Intrinsic Lens Calibrations
      • Recording Extrinsic Chessboard Calibrations
      • Recording Extrinsic Object Calibrations
    • Theia3D Interface
    • Theia3D Dropdown Menus
      • File Menu
      • Analyze Menu
      • Display Menu
      • Results Menu
      • Calibration Menu
        • Check Calibration
        • Lens Calibration
        • Chessboard Calibration
        • Object Calibration
        • Adjust Calibration
      • Tools Menu
        • Check Synchronization
        • Organize Videos
        • Format Sony Multicam
        • Assign Calibration Files
        • Modify People IDs
        • Toggle Views
        • Display Video Metadata
        • Enhance Videos
      • Settings Menu
        • Settings Menu
        • Analysis Preferences
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        • Setup Preferences
      • Help Menu
    • Theia Model Description
      • Default Model Description
      • Full Body Model Description
      • Separate Arm and Head Model Description
    • Data Formats
      • Video Data
      • Calibration Files
      • Theia3D Workspaces
      • C3D Files
      • FBX Files
      • JSON Files
      • Video Overlays
    • Theia3D Batch
      • Theia3D Batch Interface
      • Setting Up a Batch
      • File Menu
      • Help Menu
      • Settings
      • Trials
      • Preferences
      • Batch Processing Outputs
    • Camera System Requirements
    • Sony Camera Package
      • Components
      • System Setup
      • Data Collection
  • Troubleshooting
    • Troubleshooting Documentation
    • Error Messages
      • License Errors
        • License Activation Failed
      • Organize Data Errors
        • Input directory has no mp4 or avi files
      • Load Video Data Errors
        • Videos not formatted properly
        • Only [#] videos found
        • Videos are not the same length
        • Unsupported video codec detected
        • Invalid video
      • Load Calibration File Errors
        • Unable to load calibration
        • Required camera parameter groups not present
      • Load Workspace Errors
        • Selected folder does not contain a valid Theia workspace
        • Incompatible workspace
      • Calibration Errors
        • Camera extrinsics optimization step 3 failed
        • Unable to detect chessboard in overlapping frames for all cameras
        • Too few chessboards detected (<25)
        • Field of view coverage insufficient (<60%)
      • Movement Trial Processing Errors
        • Track people not complete
        • Abnormally high tracking errors
    • Visible Issues
      • Coordinate system is out of place in one camera view
      • Coordinate system is in different positions and/or orientations in all camera viewse
      • Coordinate system is in an incorrect but consistent position and/or orientation in all views
      • Skeleton is consistently outside the body
      • Skeleton is momentarily incorrect
      • Skeleton is incomplete
      • Skeleton is completely missing
      • Skeleton is jittery
    • Sony Troubleshooting
      • Initialization Issues
      • Unstable Connection
    • Other Issues
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  • Theia3D Basics
  • Calibration
  • Movement Data Collection
  • ‍Data Processing

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  1. Theia3D Documentation
  2. Getting Started

Theia3D Basics

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Last updated 1 month ago

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Theia3D Basics

Theia3D is a markerless motion capture solution that utilizes synchronized video data to produce accurate and reliable 3D pose estimates of humans visible within the video data. It leverages deep learning algorithms trained to identify humans and accurately predict the 2D positions of 124 keypoints on the human body, in every video frame of every camera. By fitting a scaled subject-specific inverse kinematic model to the keypoint predictions, the human’s pose is reconstructed in 3D and tracked throughout their movement. This data-driven approach results in a robust solution that is generalizable across environments and movements, allowing the accessible collection of high quality 3D motion capture data where it was previously impossible.

Here, we describe the basic framework for collecting markerless motion capture data using Theia3D; for more detailed instructions, please refer to the appropriate section of this documentation and any accompanying videos.

Please referr to this blog post about the

Calibration

The calibration methods supported by Theia3D include:

  • Chessboard calibration, using a large printed chessboard pattern to automatically obtain intrinsic and extrinsic camera parameters.

  • Third-party calibrations, such as wand calibrations implemented by third-party motion capture hardware suppliers.

  • Object calibration, using an object with known dimensions or with precisely measured key point positions to manually obtain extrinsic camera parameters.

Movement Data Collection

‍Data Processing

Calibration is a crucial step for any 3D motion capture solution, and is equally important for Theia3D markerless motion capture data. The recommended calibration method depends on your camera system, but the concept and result is the same across all: determine the intrinsic and extrinsic parameters for all cameras in your system. These parameters allow lens effects and the 3D position and orientation of each camera to be determined, which is the key to producing robust 3D reconstructions. See for details on recording intrinsic and extrinsic calibrations, and for details on processing calibration trials.

Once you have obtained sufficient calibration data, the next step is collecting your movement trials. Theia3D produces robust 3D pose estimates across varying environments, for humans wearing typical body-fitting clothing, and is task-agnostic. Therefore, if the human(s) in your video are clearly visible and captured with appropriate resolution, frame rate, and exposure, the Theia3D algorithms can generally track their motion without issue. Record your movement data with relative freedom and ease, following the recommendations outlined in the section.

Having collected calibration and movement trials, you have everything required to process your markerless motion capture data. Theia3D includes several tools to help organize your data as required, process and check your camera system calibration, and analyze your movement trials. If you have collected numerous movement trials, you can use the accompanying Theia3D Batch application to batch analyze your trials without active supervision on your part; however, we always recommend manually checking your calibrations and a few trials in Theia3D first. Detailed information on the Theia3D Batch companion application can be found in .

Data Collection
Calibration Menu
Data Collection Principles
Batch Processing
General Framework for Data Collections.