Quick Start for Kinect: Skeletal Tracking Fundamentals

The previous article is here: Quick Start for Kinect: Working with Depth Data

This video covers the basics of skeletal tracking using the Kinect sensor.  You may find it easier to follow along by downloading the Kinect for Windows SDK Quickstarts samples and slides that have been updated for Beta 2 (Nov, 2011).
     [00:31] Skeleton Tracking API
     [01:24] Understanding Skeleton Quality and Joint data
     [03:27] Setup skeleton tracking
     [03:44] Adding a basic hand tracked cursor
     [09:12] Using TransformSmoothing to remove “skeletal jitter”

C++


First you need to initialize a kinect sensor interface:


INuiSensor *            m_pNuiSensor;
HRESULT hr = NuiCreateSensorById( instanceName, &m_pNuiSensor );


then get one frame and detect the skeleton in this frame and find the human skeleton using both color image and depth date. The detail information is in CVPR 2011 best paper "Real-time Human Pose Recognition in Parts from Single Depth Images" . The link of this paper is here：http://research.microsoft.com/apps/pubs/default.aspx?id=145347


The C++ code is as follows:



void CSkeletalViewerApp::Nui_GotSkeletonAlert( )
{
    NUI_SKELETON_FRAME SkeletonFrame = {0};


    bool bFoundSkeleton = false;


    if ( SUCCEEDED(m_pNuiSensor->NuiSkeletonGetNextFrame( 0, &SkeletonFrame )) )
    {
        for ( int i = 0 ; i < NUI_SKELETON_COUNT ; i++ )
        {
            if( SkeletonFrame.SkeletonData[i].eTrackingState == NUI_SKELETON_TRACKED ||
                (SkeletonFrame.SkeletonData[i].eTrackingState == NUI_SKELETON_POSITION_ONLY && m_bAppTracking))
            {
                bFoundSkeleton = true;
            }
        }
    }


    // no skeletons!
    if( !bFoundSkeleton )
    {
        return;
    }


    // smooth out the skeleton data
    HRESULT hr = m_pNuiSensor->NuiTransformSmooth(&SkeletonFrame,NULL);
    if ( FAILED(hr) )
    {
        return;
    }


    // we found a skeleton, re-start the skeletal timer
    m_bScreenBlanked = false;
    m_LastSkeletonFoundTime = timeGetTime( );


    // draw each skeleton color according to the slot within they are found.
    Nui_BlankSkeletonScreen( GetDlgItem( m_hWnd, IDC_SKELETALVIEW ), false );


    bool bSkeletonIdsChanged = false;
    for ( int i = 0 ; i < NUI_SKELETON_COUNT; i++ )
    {
        if ( m_SkeletonIds[i] != SkeletonFrame.SkeletonData[i].dwTrackingID )
        {
            m_SkeletonIds[i] = SkeletonFrame.SkeletonData[i].dwTrackingID;
            bSkeletonIdsChanged = true;
        }


        // Show skeleton only if it is tracked, and the center-shoulder joint is at least inferred.
        if ( SkeletonFrame.SkeletonData[i].eTrackingState == NUI_SKELETON_TRACKED &&
            SkeletonFrame.SkeletonData[i].eSkeletonPositionTrackingState[NUI_SKELETON_POSITION_SHOULDER_CENTER] != NUI_SKELETON_POSITION_NOT_TRACKED)
        {
            Nui_DrawSkeleton( &SkeletonFrame.SkeletonData[i], GetDlgItem( m_hWnd, IDC_SKELETALVIEW ), i );
        }
        else if ( m_bAppTracking && SkeletonFrame.SkeletonData[i].eTrackingState == NUI_SKELETON_POSITION_ONLY )
        {
            Nui_DrawSkeletonId( &SkeletonFrame.SkeletonData[i], GetDlgItem( m_hWnd, IDC_SKELETALVIEW ), i );
        }
    }


    if ( bSkeletonIdsChanged )
    {
        UpdateTrackingComboBoxes();
    }


    Nui_DoDoubleBuffer(GetDlgItem(m_hWnd,IDC_SKELETALVIEW), m_SkeletonDC);
}