用Kinect查找弯头角度

Question

Vector3D Rwrist = new Vector3D(skel.Joints[JointType.WristRight].Position.X,
            skel.Joints[JointType.WristRight].Position.Y, skel.Joints[JointType.WristRight].Position.Z);
        Vector3D Relbow = new Vector3D(skel.Joints[JointType.ElbowRight].Position.X,
            skel.Joints[JointType.ElbowRight].Position.Y, skel.Joints[JointType.ElbowRight].Position.Z);
        Vector3D Rshoulder = new Vector3D(skel.Joints[JointType.ShoulderRight].Position.X,
            skel.Joints[JointType.ShoulderRight].Position.Y, skel.Joints[JointType.ShoulderRight].Position.Z);

        Vector3D wristToElbow = Vector3D.Subtract(Rwrist, Relbow);
        Vector3D elbowToShoulder = Vector3D.Subtract(Relbow, Rshoulder);

        elbowAngle = Vector3D.AngleBetween(elbowToShoulder, wristToElbow);

So it keeps returning NaN? I would really appreciate some help :) thanks so much guys!!

Answer 1

You have to normalize your Vectors. Try adding this code. I recommend that you do the AngleBetweenVector method yourself (See code below).

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 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);


            double AngleRightElbow = AngleBetweenTwoVectors(RightElbow - RightShoulder, RightElbow - RightWrist);
            double AngleLeftElbow = AngleBetweenTwoVectors(LeftElbow - LeftShoulder, LeftElbow - LeftWrist);

            byte[] Angles = {Convert.ToByte(AngleRightElbow), Convert.ToByte(AngleRightShoulder),Convert.ToByte(AngleLeftElbow),Convert.ToByte(AngleLeftShoulder)};
            return Angles;
        }
}

1. Define Vectors
2. Substract
3. Pass to AngleBetweenTwoVectors - method
4. (In AngleBetweenTwoVectors) normalize (divide by Vector length on every axis) for more information here
5. Calculate the dot product (For more here )
6. Use Arcosinus (Arcos) method
7. Product/PI*180, otherwise you would get the radian