public IEnumerable <XElement> GetSvgPaths()
        {
            Kurve.Curves.Curve curve = optimizer.GetCurve(specification);

            IEnumerable <string> curveCommands = Enumerables.Concatenate
                                                 (
                Enumerables.Create(Svg.MoveTo(curve.GetPoint(0))),
                from positions in Scalars.GetIntermediateValuesSymmetric(0, 1, SegmentCount + 1).GetRanges()
                let controlPoint1 = curve.GetPoint(positions.Item1) + (1.0 / (3 * SegmentCount)) * curve.GetVelocity(positions.Item1)
                                    let controlPoint2 = curve.GetPoint(positions.Item2) - (1.0 / (3 * SegmentCount)) * curve.GetVelocity(positions.Item2)
                                                        let point2 = curve.GetPoint(positions.Item2)
                                                                     select Svg.CurveTo(controlPoint1, controlPoint2, point2)
                                                 );

            yield return(Svg.PathShape(curveCommands, null, Colors.Black, 2));

            IEnumerable <string> curvatureMarkersCommands =
                (
                    from positions in Scalars.GetIntermediateValuesSymmetric(0, 1, SegmentCount + 1).GetRanges()
                    let position = Enumerables.Average(positions.Item1, positions.Item2)
                                   let curvatureVector = CurvatureMarkersFactor * curve.GetCurvature(position) * curve.GetNormalVector(position)
                                                         select Svg.Line(curve.GetPoint(position), curve.GetPoint(position) + curvatureVector)
                );

            yield return(Svg.PathShape(curvatureMarkersCommands, null, Colors.Blue, 0.5));

            foreach (PointCurveSpecification pointCurveSpecification in specification.BasicSpecification.CurveSpecifications.OfType <PointCurveSpecification>())
            {
                Vector2Double point = curve.GetPoint(pointCurveSpecification.Position);

                yield return(Svg.CircleShape(point, 10, Colors.Red, null, 0));
            }
            foreach (DirectionCurveSpecification directionCurveSpecification in specification.BasicSpecification.CurveSpecifications.OfType <DirectionCurveSpecification>())
            {
                Vector2Double directionVector = curve.GetDirectionVector(directionCurveSpecification.Position);
                Vector2Double start           = curve.GetPoint(directionCurveSpecification.Position) - 1000 * directionVector;
                Vector2Double end             = curve.GetPoint(directionCurveSpecification.Position) + 1000 * directionVector;

                yield return(Svg.LineShape(start, end, null, Colors.Green, 2));
            }
            foreach (CurvatureCurveSpecification curvatureCurveSpecification in specification.BasicSpecification.CurveSpecifications.OfType <CurvatureCurveSpecification>())
            {
                if (curvatureCurveSpecification.Curvature == 0)
                {
                    Vector2Double directionVector = curve.GetDirectionVector(curvatureCurveSpecification.Position);
                    Vector2Double start           = curve.GetPoint(curvatureCurveSpecification.Position) - 1000 * directionVector;
                    Vector2Double end             = curve.GetPoint(curvatureCurveSpecification.Position) + 1000 * directionVector;

                    yield return(Svg.LineShape(start, end, null, Colors.Blue, 2));
                }
                else
                {
                    Vector2Double center = curve.GetPoint(curvatureCurveSpecification.Position) - (1.0 / curvatureCurveSpecification.Curvature) * curve.GetNormalVector(curvatureCurveSpecification.Position);
                    double        radius = 1.0 / curvatureCurveSpecification.Curvature.Absolute();

                    yield return(Svg.CircleShape(center, radius, null, Colors.Blue, 2));
                }
            }
        }