[Joerg]

I tried to create ~50.000 lines with different colors. Worked, but it's very slow (displaying, rotating, zooming)
with Polyline it works fine.
Where I'm going wrong? 

// with individual color of each line -> slow

            Model3DGroup model = new Model3DGroup();
            var lineStartPos = _displayData[0];
            for (int i = 1; i < _displayData.Count; i++)
            {
                var lineEndPos = _displayData[i];
                var line = Line3DFactory.CreateLine3D(new Point3D(lineStartPos.XPos, lineStartPos.YPos, lineStartPos.ZPos),
                    new Point3D(lineEndPos.XPos, lineEndPos.YPos, lineEndPos.ZPos), 2, lineEndPos.Color,
                    LineCap.Flat, LineCap.Flat, MainViewport);
                model.Children.Add(line);
                lineStartPos = lineEndPos;
            }
            CurveModelVisual.Content = model;

// with same color for each line -> fast
            //List<Point3D> allPositions = new List<Point3D>();
            //foreach (var positionData in _allSpheresData)
            //{
            //    allPositions.Add(positionData.Position);
            //}
            //BezierCurve bezierCurve = BezierCurve.CreateFromCurvePositions(allPositions);
            //Point3DCollection curvePoints = bezierCurve.CreateBezierCurve(positionsPerSegment: 1); 
            //Model3D curveModel = Line3DFactory.CreatePolyLine3D(curvePoints, thickness: 2, color: Colors.Blue, isClosed: false, startLineCap: LineCap.Flat, endLineCap: LineCap.Flat, parentViewport3D: MainViewport);
            //CurveModelVisual.Content = curveModel;