Accord.Imaging.RansacFundamentalEstimator.distance C# (CSharp) Method

        private int[] distance(float[,] F, double t)
        {
            int n = pointSet1.Length;

            PointF[] x1 = pointSet1;
            PointF[] x2 = pointSet2;

            double[] x2tFx1 = new double[n];
            for (int i = 0; i < x1.Length; i++)
            {
                float[] a = x2[i].Multiply(F);
                float[] b = new float[] { x1[i].X, x1[i].Y, 1 };
                x2tFx1[i] = a.Dot(b);
            }


            PointF[] p1 = F.TransformPoints(x1);
            PointF[] p2 = F.Transpose().TransformPoints(x2);

            // Compute the distances
            double[] d2 = new double[n];
            for (int i = 0; i < n; i++)
            {
                // Compute the distance as
                float ax = p1[i].X;
                float ay = p1[i].Y;

                float bx = p2[i].X;
                float by = p2[i].Y;

                d2[i] = (x2tFx1[i] * x2tFx1[i]) / ((ax * ax) + (ay * ay) + (bx * bx) + (by * by));
            }

            // Find and return the inliers
            return Matrix.Find(d2, z => Math.Abs(z) < t);
        }