SS5305 – Data Cleaning and Output 1

Objectives Skeletal Hierarchy Marker Data Position Re-targeting Data Cleaning Motion Reconstruction Data Output and Import 2

Motion Capture Workflow automated by most mocap systems

Two views can uniquely determine a 3D point in space. Intersection of lines in space through the image points gives three dimensional position of the marker. Motion Capture Basics

Retargeting Given Mx,My,Mz – Marker position in world Find Rx,Ry,Rz – Angles for Joint 1 Simple method: 1. Transform Joint 1 to origin using Joint 0 inverse basis transform 2. Use trigonometry to calculate 3D angles from position World spaceJoint 1 space Joint 0 transform

Problem: Markers are on the outside of the joints. Solution: Think of markers as moving rigidly on a sphere. What is the center and motion of the sphere? Static sphere: Radius and motion cannot be determined. Rotating sphere: Radius and motion can be found over time. Markers are constrained. Retargeting – Rotating Sphere

Define one or more markers to be on a sphere centered on each joint. Use least squares to fit the skeleton inside the markers, with constraints. L. Herda, P. Fua, R. Pl¨ankers, R. Boulic and D. Thalmann, Skeleton-Based Motion Capture for Robust Reconstruction of Human Motion. Computer Animaiton, 2000 Reconstruction of Motion

Why? Causes of error: - Incorrect calibration (usually fix this, don’t data clean) - Calibration accuracy - Video noise - Camera shake - Camera focus - Lighting conditions - Line intersection error (magnifies errors) When? Data cleaning takes time. Best way is to avoid bad data. Good calibration. Lots of cameras. Some occlusion may still occur. What? Clean marker data.. Don’t clean joint data. Data Cleaning

Remove spikes From: Midori Kitagawa & Brian Windsor, MoCap for Artists: Workflow and Techniques for Motion Capture. Focal Press, 2008 What would a spike look like on an animated character? Data Cleaning - Operations

Remove gaps (caused by occlusion) From: Midori Kitagawa & Brian Windsor, MoCap for Artists: Workflow and Techniques for Motion Capture. Focal Press, 2008 What would a gap look like on an animated character? Data Cleaning - Interpolation

From: Midori Kitagawa & Brian Windsor, MoCap for Artists: Workflow and Techniques for Motion Capture. Focal Press, 2008 Remove noise What would noise look like on an animated character? Data Cleaning - Noise

Typical output of a Motion Capture session is: - A joint hierarchy - Body translation (root joint) over time - Joint rotations over time for all joints Data Formats:.C3DNational Inst. of Health Used in Biotech Binary data (large amonts), Analog also.ASFAcclaim, Inc. (closed 2004). – Joint hierarchyUsed by Vicon.AMCAcclain, Inc. – Joint motion, and original 3D User by Vicon.BVABiovision – Contains motion onlyObsolete.BVHBiovision – Contains hierarchy and motionWidely used. Simple..FBXOriginally FilmBox, became MotionBuilderWidely used. Universal. Contains textures, geometry, motion, etc..MAMaya – Stores data as script commandsWidely used. Universal. Contains textures, geometry, motion, etc..MBMaya – Binary format. Not directly readable. Data Output and Formats

What you need: Put file here: man_cap.maMaya mocap rig imocaputilz.mllBVH Import plug-in\Maya8.0\bin\plug-ins imocapImportOptions.melBVH Import options\Maya8.0\scripts\startup joint_map.melJoint renaming script\Maya8.0\scripts\startup joint_map.txtJoint renaming input data.bvhBVH mocap data Available in mini-module as mocap_files.zip Data Import

QTM 2D => 3D Data acquisition & synchronization 2D Capture Force data 3D, force, EMG data Export => c3d, tsv PAF for ALL High Speed Video Report Visualization & Motion analysis Human Motion model Signal processing Visual3D = Kinematics + Kinetics + EMG EMG PAF – Project Automation Framework

Major components of Qualisys system: Oqus - Motion Capture Camera Tracking movements in 3D with infrared technology Data processing, analysis and visualization: Visual3D and Motion Monitor - biomechanical analysis and report generation Motion Builder, 3DStudioMax, Maya – RT visualization and animation production Matlab, LabView, Excel - complex mathematic calculations. QTM – Qualisys Track Manager Calibration and 3D tracking Data collection and cleaning Automatic identification of markers Synchronization with external equipment (force plates, EMG etc.) 3D Data real-time streaming (to Visual3D, Motion Builder, Matlab, LabView) Data export to various formats (c3d, tsv, avi etc)

QTM – Qualisys data acquisition software Compatible with all generations of cameras  Calibration  Capture using the Qualisys cameras  3D data Reconstruction &Tracking  Automatic Identification of Markers (AIM)  Export to c3d-, tsv-files or directly to Matlab Modern and easy-to-use GUI Real-time preview of 2-D & 3-D data Real-time 3D data streaming Integrated video capture support OPEN FACULTY LICENSE – UNLIMITED NUMBER OF INSTALLATIONS

QTM Project Automation Framework Purpose: automate repetitive data collection and analysis Link data collection to processing in Visual3D QTM PAF 1.0 QTM PAF 1.0 Patient info Select analysis Set of Trials c3d Report in Word Report in Word Return of data Calculate data Data collection Excel Visual3D Calculation Visual3D Calculation

PAF – Interface overview Data tree Details for selected item Data collection buttons PAF comes with powerful tools for managing client metadata (height, weight and birth date) which can easily be entered and changed directly in QTM. The data is stored in a simple, transparent file hierarchy, making it easy and hassle-free to move the data across disks and computers.

Facilities Main laboratory: 35m x 12m (3D motion running track) 35 m running track surface

Video / Motion Capture / Animation

Motion Capture with 50 cameras on 3 subjects