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SS5305 – Data Cleaning and Output

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Objectives

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

Motion Capture Workflow

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4. 5. 6. 7.

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 worldFind Rx,Ry,Rz – Angles for Joint 1

Simple method:1. Transform Joint 1 to origin using Joint 0 inverse basis transform2. Use trigonometry to calculate 3D angles from position

World space Joint 1 spaceJoint 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 canbe 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 spikelook like on ananimated 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 gaplook like on ananimated 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 noiselook like on ananimated 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:

.C3D National Inst. of Health Used in BiotechBinary data (large amonts), Analog also

.ASF Acclaim, Inc. (closed 2004). – Joint hierarchy Used by Vicon

.AMC Acclain, Inc. – Joint motion, and original 3D User by Vicon

.BVA Biovision – Contains motion only Obsolete

.BVH Biovision – Contains hierarchy and motion Widely used. Simple.

.FBX Originally FilmBox, became MotionBuilder Widely used. Universal.Contains textures, geometry, motion, etc.

.MA Maya – Stores data as script commands Widely used. Universal.Contains textures, geometry, motion, etc.

.MB Maya – Binary format. Not directly readable.

Data Output and Formats

What you need:

Put file here:

man_cap.ma Maya mocap rig

imocaputilz.mll BVH Import plug-in \Maya8.0\bin\plug-insimocapImportOptions.mel BVH Import options \Maya8.0\scripts\startupjoint_map.mel Joint renaming script \Maya8.0\scripts\startup joint_map.txt Joint renaming input

data.bvh BVH mocap data

Available in mini-module as mocap_files.zip

Data Import

QTM 2D => 3D

Data acquisition & synchronization2D 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 GUIReal-time preview of 2-D & 3-D dataReal-time 3D data streamingIntegrated 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

QTMPAF 1.0

Patient infoSelect analysis

Set of Trials c3d

Report in Word

Return of data

Calculate data

Data collection

Excel

Visual3DCalculation

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.

Fac

ilitie

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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