Question

I’m currently trying to track a users face using xbox kinect. I have taken some of the code from “Face tracking basics” and to store the location of the points it uses:

            var faceModelPts = new List<Point>();
            var faceModel = new List<FaceModelTriangle>();

            for (int i = 0; i < this.facePoints.Count; i++)
            {
                faceModelPts.Add(new Point(this.facePoints[i].X + 0.5f, this.facePoints[i].Y + 0.5f));
            }

I want to be able to use the information to calculate the distance between some of these points. So I have tried putting them in a separate array like this:

            var faceModelPts = new List<Point>();
            var faceModel = new List<FaceModelTriangle>();
            double[] xarray;
            double[] yarray;

            for (int i = 0; i < this.facePoints.Count; i++)
            {
                faceModelPts.Add(new Point(this.facePoints[i].X + 0.5f, this.facePoints[i].Y + 0.5f));
                xarray[i] = this.facePoints[i].X;
                yarray[i] = this.facePoints[i].Y;
            }

but this seems to return errors. But I can get the information by doing the following:

            double xpos21 = this.facePoints[21].X;

Is there just a simple error in what i’m doing or can this information not be placed into an array this way?

Also once I have the positions of the points how do I go about retrieving the depth information at this location?

Answer 1

You do not appear to be initializing your arrays.

xarray = new double[someSize];
yarray = new double[someSize];

That would explain the null pointer in your array, unless you’re declaring this outside your quoted code.

Set a breakpoint on that line in Visual Studio. When you hit it during a Debug, check to verify that xarray is not null.