[vtkusers] Draw 2D Ellipse annotation/overlay over a 2D graphics object

[NIPL]

Hi all,
I want to draw a 2D ellipse annotation over a DICOM image loaded in a 2D
View.
There is no builtin function/class for ellipse. But there is a
vtkSphereSource and it is 3D. Can I derive a 2D ellipse from it by using
vtkPolyDataMapper2D? I tried using the vtkPoints first and have some issues.
I am using the vtkDotnet wrapper for c#.
I have done like this:
Method 1:
                 vtk.vtkPoints ellipsePoints = new vtk.vtkPoints();
                double angle = 0;
                double r1, r2;
                int id = 0;
                int CenterX = 0, CenterY = 0;
                CenterX = 100; 
                CenterY = 100; 
                r1 = 40;
                r2 = 20;
 
                while (angle <= 2F * Math.PI + (Math.PI / 30F))
                {
           ellipsePoints.InsertPoint(id, r1 * Math.Cos(angle) + CenterX, r2
* Math.Sin(angle) + CenterY, 0);
                    angle = angle + (Math.PI / 30F);
                    id++;
                }
                vtk.vtkPolyLine ellipse = new vtk.vtkPolyLine();
                ellipse.GetPointIds().SetNumberOfIds(id);
 
                for (int i = 0; i < id; i++)
                {
                    ellipse.GetPointIds().SetId(i, i);
 
                }

                vtk.vtkUnstructuredGrid grid = new
vtk.vtkUnstructuredGrid();
                grid.Allocate(1, 1);
                grid.InsertNextCell(ellipse.GetCellType(),
ellipse.GetPointIds());
                grid.SetPoints(ellipsePoints);
                grid.Update();

                vtk.vtkDataSetMapper m = new vtk.vtkDataSetMapper();
                m.SetInput(grid);
                m.SetColorModeToMapScalars();

                vtk.vtkActor aSphere = new vtk.vtkActor();
                aSphere.SetMapper(m);
                aSphere.GetProperty().SetColor(0, 0, 1); // color blue
                aSphere.GetProperty().SetInterpolationToFlat();
                aSphere.VisibilityOn();
                // a renderer for the data
                //vtk.vtkRenderer ren1 = new vtk.vtkRenderer();
                irenderer.AddActor(aSphere);
                 iwindow.Render();

But the ellipse is no visible while i draw.

Method 2:
                vtk.vtkSphereSource vtkEllipse = new vtk.vtkSphereSource();
                vtkEllipse.SetRadius(100);
                vtkEllipse.SetCenter(100, 100, 0);
                vtkEllipse.SetThetaResolution(360);
                vtkEllipse.SetPhiResolution(90);
                vtkEllipse.SetEndPhi(90);
                vtkEllipse.SetStartPhi(70);
                vtk.vtkTransformPolyDataFilter tf = new
vtk.vtkTransformPolyDataFilter();
                vtk.vtkTransform tr = new vtk.vtkTransform();
                tr.Identity();
                tf.SetInput(vtkEllipse.GetOutput());
                tf.SetTransform(tr);
                tf.Update();
                vtk.vtkPolyDataMapper2D m = new vtk.vtkPolyDataMapper2D();
                vtk.vtkActor2D vtkActor = new vtk.vtkActor2D();
                m.SetInput(tf.GetOutput());
                vtkActor.SetMapper(m);
                vtkActor.VisibilityOn();
                vtkActor.GetProperty().SetColor(1, .5, 0);
                irenderer.AddViewProp(vtkActor);
                iwindow.Render();
But this is not what i want. the line width is not correct.

Method 3:
                double angle = 0;
                double r1, r2;
                int id = 0;
                int CenterX , CenterY;
                CenterX = 100; 
                CenterY = 100; 
                r1 = 40;
                r2 = 20;

                vtk.vtkPoints ellipsePoints = new vtk.vtkPoints();
                ellipsePoints.SetNumberOfPoints(31);
                while (angle <= 2F * Math.PI + (Math.PI / 30F))
                {
                    ellipsePoints.SetPoint(id, r1 * Math.Cos(angle) +
CenterX, r2 * Math.Sin(angle) + CenterY, 0);
                    angle = angle + (Math.PI / 30F);
                    id++;
                }
                //id = ellipsePoints.GetNumberOfPoints();
                vtk.vtkCellArray c_lines = new vtk.vtkCellArray();
                c_lines.Allocate(1, 1);
                c_lines.InsertNextCell(id);
                c_lines.SetNumberOfCells(id);
                for (int k = 0; k < id; ++k)
                    c_lines.InsertCellPoint(k);

                vtk.vtkPolyData c_polyData = new vtk.vtkPolyData();
                c_polyData.ReleaseDataFlagOn();
                c_polyData.Allocate(1, 1);
                c_polyData.SetPoints(ellipsePoints);
                c_polyData.SetLines(c_lines);

                vtk.vtkPolyDataMapper2D c_polyDataMapper = new
vtk.vtkPolyDataMapper2D();
                c_polyDataMapper.SetInput(c_polyData);

                vtk.vtkActor2D c_actor = new vtk.vtkActor2D();

                //c_actor.GetProperty().SetOpacity(.50);
                //c_actor.GetProperty().SetLineWidth(2.0f);

                c_actor.SetMapper(c_polyDataMapper);
                c_actor.VisibilityOn();
                c_actor.GetProperty().SetColor(1, .5, 0);
                irenderer.AddViewProp(c_actor);

                iwindow.Render();
                c_polyData.Dispose();
                c_lines.Dispose();
                ellipsePoints.Dispose();

This one is working fine. I can see the ellipse and it looks great. But when
I draw a second ellipse on same image, it crashes. The constructor returns
null pointer.

Is my logic correct or am I missing something? The Method 1 is not crashing
but it is is not visible. Can anyone please help me fixing it?

Thanks in advance.
-- 
View this message in context: http://www.nabble.com/Draw-2D-Ellipse-annotation-overlay-over-a-2D-graphics-object-tp22034221p22034221.html
Sent from the VTK - Users mailing list archive at Nabble.com.