Which one represent AutoCAD's Spline？BezierCurve，BezierCurveCubic，BSplineCurve...

[my88480]

Which one represent AutoCAD's Spline？

I assumed it is BezierCurveCubic.but ....

the code: DxfDocument dxfDoc = new DxfDocument();

        List<Vector3> controlPoints = new List<Vector3>();
        List<double> weights = new List<double>();
        short degree = 3;

        controlPoints.Add(new Vector3(1.0, 1.0, 0.0));
        controlPoints.Add(new Vector3(9.5, 3.0, 0.0));
        controlPoints.Add(new Vector3(7.5, 8.0, 0.0));
        controlPoints.Add(new Vector3(2.5, 4.5, 0.0));
        controlPoints.Add(new Vector3(0.5, 8.0, 0.0));
        controlPoints.Add(new Vector3(5.5, 9.0, 0.0));
        controlPoints.Add(new Vector3(6.5, 0.5, 0.0));

        weights.Add(1.0);
        weights.Add(1.0);
        weights.Add(1.0);
        weights.Add(1.0);
        weights.Add(1.0);
        weights.Add(1.0);
        weights.Add(1.0);

        Spline spline = new Spline(controlPoints, weights, degree);

        dxfDoc.Entities.Add(spline);

        controlPoints = new List<Vector3>();
        controlPoints.Add(new Vector3(1.0, 1.0, 0.0));
        controlPoints.Add(new Vector3(1.0, 1.0, 0.0));
        controlPoints.Add(new Vector3(9.5, 3.0, 0.0));
        controlPoints.Add(new Vector3(7.5, 8.0, 0.0));
        controlPoints.Add(new Vector3(2.5, 4.5, 0.0));
        controlPoints.Add(new Vector3(0.5, 8.0, 0.0));
        controlPoints.Add(new Vector3(5.5, 9.0, 0.0));
        controlPoints.Add(new Vector3(6.5, 0.5, 0.0));
        controlPoints.Add(new Vector3(6.5, 0.5, 0.0));

        BezierCurveCubic cube = new BezierCurveCubic(controlPoints);
        int n = 20;

        for (double t = 0.0;t<= 1.0;t=t+1.0/(n-1))
        {
            Vector3 vec = cube.CalculatePoint(t);

            netDxf.Entities.Point point = new netDxf.Entities.Point(vec);
            point.Color = AciColor.FromCadIndex(3);

            dxfDoc.Entities.Add(point);
        }

        dxfDoc.Save("Spline_demo.dxf");

        MessageBox.Show("Done.");

[haplokuon]

AutoCAD Spline is a NURBS (Non-Uniform Rational B-Spline) curve. A NURBS can precisely represent a conic, a bezier, or a b-spline, but it is not possible the other way around.

A cubic bezier curve is made of 4 control points, I should have added a check for that, but you should read the documentation.

[my88480]

        short degree = 3;

        List<Vector3> controls = new List<Vector3>
        {
        new Vector3(1.0, 1.0, 0.0),
        new Vector3(9.5, 3.0, 0.0),
        new Vector3(7.5, 8.0, 0.0),
        new Vector3(2.5, 4.5, 0.0),
        new Vector3(0.5, 8.0, 0.0),
        new Vector3(5.5, 9.0, 0.0),
        new Vector3(6.5, 0.5, 0.0)
    };

        double[] weights = new double[controls.Count];
        double weigth = 1.0;
        for (int i = 0; i < weights.Length; i++)
        {
            weights[i] = weigth;
            //weigth *= 5;
        }

        netDxf.GTE.BasisFunctionInput input = new netDxf.GTE.BasisFunctionInput(controls.Count, degree);
        netDxf.GTE.NURBSCurve curve = new netDxf.GTE.NURBSCurve(input, controls.ToArray(), weights);

        int pointCount = 101;
        double step = 1.0 / (pointCount - 1.0);
        Vector3[] vertexes = new Vector3[pointCount];
        Vector3[] tangents = new Vector3[pointCount];
        for (int i = 0; i < pointCount; i++)
        {
            vertexes[i] = curve.GetPosition(i * step);
            tangents[i] = curve.GetTangent(i * step);
        }

        Spline spline = new Spline(controls, weights, degree) { Color = AciColor.Blue };
        Polyline3D polyline = new Polyline3D(vertexes) { Color = AciColor.Red };

        DxfDocument doc = new DxfDocument();
        doc.Entities.Add(spline);
        doc.Entities.Add(polyline);
        doc.Save("Spline_demo2.dxf");

        MessageBox.Show("Done.");

That is it. and also get the tangent.

[DavidWishengrad]

noted thank you