Kinect-Matlab: Get joint angle information - matlab

Question

I am a beginner at kinect and I want to use it with matlab. I need joint angle information out of the skeleton data. What is the easiest way to do this?
Thanks.

Answer 1

I am not good with Mat lab, but try to use c# with Visual Studio. Use the SkeletonBasics-WPF in the Microsoft SDK´s as a template to add this code:
public class Angles
{
public double AngleBetweenTwoVectors(Vector3D vectorA, Vector3D vectorB)
{
double dotProduct;
vectorA.Normalize();
vectorB.Normalize();
dotProduct = Vector3D.DotProduct(vectorA, vectorB);
return (double)Math.Acos(dotProduct)/Math.PI*180;
}
public byte[] GetVector(Skeleton skeleton)
{
Vector3D ShoulderCenter = new Vector3D(skeleton.Joints[JointType.ShoulderCenter].Position.X, skeleton.Joints[JointType.ShoulderCenter].Position.Y, skeleton.Joints[JointType.ShoulderCenter].Position.Z);
Vector3D RightShoulder = new Vector3D(skeleton.Joints[JointType.ShoulderRight].Position.X, skeleton.Joints[JointType.ShoulderRight].Position.Y, skeleton.Joints[JointType.ShoulderRight].Position.Z);
Vector3D LeftShoulder = new Vector3D(skeleton.Joints[JointType.ShoulderLeft].Position.X, skeleton.Joints[JointType.ShoulderLeft].Position.Y, skeleton.Joints[JointType.ShoulderLeft].Position.Z);
Vector3D RightElbow = new Vector3D(skeleton.Joints[JointType.ElbowRight].Position.X, skeleton.Joints[JointType.ElbowRight].Position.Y, skeleton.Joints[JointType.ElbowRight].Position.Z);
Vector3D LeftElbow = new Vector3D(skeleton.Joints[JointType.ElbowLeft].Position.X, skeleton.Joints[JointType.ElbowLeft].Position.Y, skeleton.Joints[JointType.ElbowLeft].Position.Z);
Vector3D RightWrist = new Vector3D(skeleton.Joints[JointType.WristRight].Position.X, skeleton.Joints[JointType.WristRight].Position.Y, skeleton.Joints[JointType.WristRight].Position.Z);
Vector3D LeftWrist = new Vector3D(skeleton.Joints[JointType.WristLeft].Position.X, skeleton.Joints[JointType.WristLeft].Position.Y, skeleton.Joints[JointType.WristLeft].Position.Z);
Vector3D UpVector = new Vector3D(0.0, 1.0, 0.0);
double AngleRightElbow = AngleBetweenTwoVectors(RightElbow - RightShoulder, RightElbow - RightWrist);
double AngleRightShoulder = AngleBetweenTwoVectors(UpVector, RightShoulder - RightElbow);
double AngleLeftElbow = AngleBetweenTwoVectors(LeftElbow - LeftShoulder, LeftElbow - LeftWrist);
double AngleLeftShoulder = AngleBetweenTwoVectors(UpVector, LeftShoulder - LeftElbow);
byte[] Angles = {Convert.ToByte(AngleRightElbow), Convert.ToByte(AngleRightShoulder),Convert.ToByte(AngleLeftElbow),Convert.ToByte(AngleLeftShoulder)};
return Angles;
}
}
Insert this at the top. Call the GetVector() method here:
private void SensorSkeletonFrameReady(object sender, SkeletonFrameReadyEventArgs e)
{
Skeleton[] skeletons = new Skeleton[0];
using (SkeletonFrame skeletonFrame = e.OpenSkeletonFrame())
{
if (skeletonFrame != null)
{
skeletons = new Skeleton[skeletonFrame.SkeletonArrayLength];
skeletonFrame.CopySkeletonDataTo(skeletons);
}
}
using (DrawingContext dc = this.drawingGroup.Open())
{
// Draw a transparent background to set the render size
dc.DrawRectangle(Brushes.Black, null, new Rect(0.0, 0.0, RenderWidth, RenderHeight));
if (skeletons.Length != 0)
{
foreach (Skeleton skel in skeletons)
{
RenderClippedEdges(skel, dc);
if (skel.TrackingState == SkeletonTrackingState.Tracked)
{
this.DrawBonesAndJoints(skel, dc);
Angles MyAngles = new Angles();
byte[] ReadyAngles = MyAngles.GetVector(skel);
RightElbow.Text = ReadyAngles[0].ToString();
RightShoulder.Text = ReadyAngles[1].ToString();
LeftElbow.Text = ReadyAngles[2].ToString();
LeftShoulder.Text = ReadyAngles[3].ToString();
byte[] SequenceStart = {255};
if (ArduinoPort.IsOpen)
{
ArduinoPort.Write(SequenceStart,0,1);
ArduinoPort.Write(ReadyAngles, 0, 4);
}
}
else if (skel.TrackingState == SkeletonTrackingState.PositionOnly)
{
dc.DrawEllipse(
this.centerPointBrush,
null,
this.SkeletonPointToScreen(skel.Position),
BodyCenterThickness,
BodyCenterThickness);
}
}
}
// prevent drawing outside of our render area
this.drawingGroup.ClipGeometry = new RectangleGeometry(new Rect(0.0, 0.0, RenderWidth, RenderHeight));
}
}
As you can see I added 4 textboxes as I am calculating 4 Angles (RS, LF, RE, LE). These Angles are being passed to the textbox in my .xaml file. I hope this works for you.

Answer 2

You would need the Image Acquisition Toolbox, which includes support for Kinect including skeleton data.