Hi,<br><br>Thanks. Ya, I will try to visualize this. Hopefully this will provide some clues.<br><br>There is something very weird going on... For simple triangle data, the lines seem to become parallel.... and I am getting a really screwy stenciled shape. I will look into it and try to figure it out. Will keep the list updated.
<br><br>Cheers and thanks again,<br>Anja<br><br><div><span class="gmail_quote">On 25/10/06, <b class="gmail_sendername">Dean Inglis</b> <<a href="mailto:dean.inglis@camris.ca">dean.inglis@camris.ca</a>> wrote:</span>
<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">Anja,<br><br>sorry, I didn't look closely at your points: I thought<br>they formed a square/rectangle. So the code for vtkCellArray
<br>really should be as you show below. The z offset is<br>necessary for the vtkPolyDataToImageStencil to work:<br>it does not work with polylines, but needs surfaces,<br>so the extrusion makes a "ribbon". If you pass the polyData
<br>output of the extrusion filter to a vtkPolyDataMapper/vtkActor<br>and visualize it you will see what I mean. This will also<br>help with unserstanding possible errors: make sure your image<br>actor can be manipulated with a interactorStyleTrackballCamera
<br>and not interactorStyleImage. Also, I would change the background color<br>of your renerwindow to something other than black. If your 2D (?) image<br>has z-thickness, you may have to change the z offset and<br>extrusion scale. Also, if the triangle is too acute relative
<br>to the pixel dimensions, or if your closed polydata loops back on<br>itself or has "knots", you can get erroneous results.<br><br>Dean<br><br><br>-----Original Message-----<br>From: Anja Ende [mailto:<a href="mailto:anja.ende@googlemail.com">
anja.ende@googlemail.com</a>]<br>Sent: Wednesday, October 25, 2006 9:16 AM<br>To: Dean's business account<br>Cc: <a href="mailto:vtkusers@vtk.org">vtkusers@vtk.org</a><br>Subject: Re: [vtkusers] vtkPolyData to be used with vtkImageStencil.
<br><br><br>Another question that I wanted to ask is why do we set the z offset?<br>Clearly, this is needed as the output is completely different... But what<br>does it actually do?<br><br>Thanks,<br>Anja<br><br><br>On 25/10/06, Anja Ende <
<a href="mailto:anja.ende@googlemail.com">anja.ende@googlemail.com</a>> wrote:<br>Hi Dean,<br><br>Thanks for the reply and code fragmant. This really helps!<br><br>Your suggestiosn were completely on the money (as usual!). It was the
<br>problem with not closing the loop and the extrusion vector just being copied<br>and pasted from example code without bothering to understand what it meant!<br><br>However, there seems to be a problem with the stencil output:
<br><br>The points I have chosen are:<br><br>float pts[4][3] = {{-55.7812, 9.375, -0.5},<br> {-18.2812, 49.6875, -0.5},<br> { 21.0938, 14.0625, -0.5},<br> {-55.7812, 9.375, -0.5
}};<br><br>which should form a triangle.<br><br>However, the output looks very weird. The triangle is too small and very<br>jagged. Also, the dimensions of the triangle seem wrong. There is a<br>screenshot attached with this message. Please mail me if you cannot see it
<br>on the website and I will send you the screenshot immediately.<br><br>Also, here is the latest code now:<br><br>float pts[4][3] = {{-55.7812, 9.375, -0.5},<br> {-18.2812, 49.6875, -0.5},<br> {
21.0938, 14.0625, -0.5},<br> {-55.7812, 9.375 , - 0.5}};<br><br>vtkFloatArray* pcoords = vtkFloatArray::New();<br>pcoords->SetNumberOfComponents(3);<br>pcoords->SetNumberOfTuples(4);<br>for (int i=0; i<4; i++)
<br>{<br> pcoords->SetTuple(i, pts[i]);<br>}<br>// Create vtkPoints and assign pcoords as the internal data array.<br>vtkPoints* points = vtkPoints::New();<br>points->SetData(pcoords);<br>vtkPolyData* polydata = vtkPolyData::New();
<br>polydata->SetPoints(points);<br><br><br> vtkCellArray* strips = vtkCellArray::New();<br> strips->InsertNextCell(4);<br> strips->InsertCellPoint(0);<br> strips->InsertCellPoint(1);<br> strips->InsertCellPoint(2);
<br> strips->InsertCellPoint(3); // same coordinates as the first one..<br><br>polydata->SetStrips(strips);<br><br>vtkLinearExtrusionFilter* extrude = vtkLinearExtrusionFilter::New();<br>extrude->SetInput(polydata);
<br>extrude->SetScaleFactor(1);<br>extrude->SetExtrusionTypeToNormalExtrusion();<br>extrude->SetVector(0, 0, 1);<br><br>vtkPolyDataToImageStencil* dataToStencil = vtkPolyDataToImageStencil::New();<br>dataToStencil->SetInput(extrude->GetOutput());
<br><br>vtkImageStencil* stencil = vtkImageStencil::New();<br>stencil->SetInput(m_viewer->GetOutput());<br>stencil->SetStencil(dataToStencil->GetOutput());<br>stencil->ReverseStencilOn();<br>stencil->SetBackgroundValue(0);
<br><br>stencil->Update();<br><br>Also, when I add more points, so instead of a triangle have a quadrilateral.<br>I see a triangle shape being stencilled and the outside the loop some lines<br>through the image... but they are completely outside the loop. However, I
<br>can see that the shape is completely closed....<br><br>Thanks for all the help!<br><br>Anja<br><br><br><br><br><br>--<br>Cheers,<br><br>Anja<br></blockquote></div><br><br clear="all"><br>-- <br>Cheers,<br><br>Anja