[vtkusers] Rendering/Computing normals of a surface

Mon Apr 15 12:47:00 EDT 2013

Have you set the ScalarRange on the Mapper? You should set it to the range
of your scalar data. If you do not want to display scalar colors, apply
SetScalarVisibilityOff() to your mapper.

On Mon, Apr 15, 2013 at 11:51 AM, Kilgus, Thomas <
t.kilgus at dkfz-heidelberg.de> wrote:

> Hey Bill,****
>
> ** **
>
> I just figured out that the normals of my Kinect data are indeed there.
> They are just rendered very small and in dark blue on a black renderwindow.
> I set the color of the actor to red and don’t use the SetColorMode method
> of the glyph3d (I tried to use it, but it didn’t change anything). The
> normals of my ball are rendered in red. Do you have any idea why my Kinect
> data has blue glyphs and ignores all color calls? Does this “blue” have any
> meaning? ****
>
> ** **
>
> Regards,****
>
> Thomas****
>
> ** **
>
> *From:* Bill Lorensen [mailto:bill.lorensen at gmail.com]
> *Sent:* Freitag, 12. April 2013 16:44
>
> *To:* Kilgus, Thomas
> *Cc:* vtkusers at vtk.org
> *Subject:* Re: [vtkusers] Rendering/Computing normals of a surface****
>
> ** **
>
> The mapping is 1:1. There will be a normal for each point and a normal for
> each cell.****
>
> ** **
>
> ** **
>
> On Fri, Apr 12, 2013 at 10:30 AM, Kilgus, Thomas <
> t.kilgus at dkfz-heidelberg.de> wrote:****
>
> Sorry, either this example is not the answer to my question or I don’t get
> it :). ****
>
>  ****
>
> I have N normals inside a vtkDoubleArray and V vertices inside a
> vtkPolyData. How can I get the corresponding normal(s) N(j) to vertex V(i).
> I think i != j, because when splitting is on NumberOfNormals !=
> NumberOfVertices, or not? In other words, the mapping is NOT 1:1. ****
>
>  ****
>
> The example simply adds 3 normals to 3 points and here the mapping is 1:1.
> ****
>
>  ****
>
> *From:* Bill Lorensen [mailto:bill.lorensen at gmail.com]
> *Sent:* Freitag, 12. April 2013 16:21****
>
>
> *To:* Kilgus, Thomas
> *Cc:* vtkusers at vtk.org
> *Subject:* Re: [vtkusers] Rendering/Computing normals of a surface****
>
>  ****
>
> Look at this example:****
>
> http://vtk.org/Wiki/VTK/Examples/Cxx/PolyData/PolyDataPointNormals****
>
>  ****
>
>  ****
>
> On Fri, Apr 12, 2013 at 9:04 AM, Kilgus, Thomas <
> t.kilgus at dkfz-heidelberg.de> wrote:****
>
> And how would I get the normal of a certain vertex? Especially with
> SplittingOn()****
>
>  ****
>
> *From:* Bill Lorensen [mailto:bill.lorensen at gmail.com]
> *Sent:* Freitag, 12. April 2013 14:57****
>
>
> *To:* Kilgus, Thomas
> *Cc:* vtkusers at vtk.org
> *Subject:* Re: [vtkusers] Rendering/Computing normals of a surface****
>
>  ****
>
> 2) vtkPlaneSource generates normals. Many of the source's do.****
>
>  ****
>
> After****
>
>  normalGenerator->Update();****
>
> try****
>
> normalGenerator->GetOutput()->Print(std::cout);****
>
> to see if there are normals present****
>
>  ****
>
>  ****
>
>  ****
>
> On Fri, Apr 12, 2013 at 8:45 AM, Kilgus, Thomas <
> t.kilgus at dkfz-heidelberg.de> wrote:****
>
> Unfortunately, that is a bit complicated and inside our own framework. But
> basically, this happens:****
>
>  ****
>
> vtkSmartPointer<vtkPoints> points = vtkSmartPointer<vtkPoints>::New();****
>
> points->SetDataTypeToDouble();****
>
> vtkSmartPointer<vtkCellArray> polys = vtkSmartPointer<vtkCellArray>::New();
> ****
>
>  ****
>
> for loop for all pixels of the depth image****
>
> {****
>
> Insert 3d point into points****
>
>  ****
>
> Insert cell points for valid (!=0) points with valid neighbors (simple
> triangulation)****
>
> }****
>
>  ****
>
> vtkSmartPointer<vtkPolyData> mesh = vtkSmartPointer<vtkPolyData>::New();**
> **
>
> mesh->SetPoints(points);****
>
> mesh->SetPolys(polys);****
>
>  ****
>
> We also add texture coordinates and scalars, but this is not related to
> normals, is it?****
>
>  ****
>
> You can see the details here:
> http://mitk.org/git/?p=MITK.git;a=blob;f=Modules/ToFProcessing/mitkToFDistanceImageToSurfaceFilter.cpp;h=2b24b193315c2db97bce1d4f8aed90df42c99d1f;hb=HEAD
> ****
>
>  ****
>
> My questions 3. and 4.  are not related to the Kinect data, are they?****
>
>  ****
>
> Regards,****
>
> Thomas****
>
>  ****
>
>  ****
>
>  ****
>
> *From:* Bill Lorensen [mailto:bill.lorensen at gmail.com]
> *Sent:* Freitag, 12. April 2013 14:36
> *To:* Kilgus, Thomas
> *Cc:* vtkusers at vtk.org
> *Subject:* Re: [vtkusers] Rendering/Computing normals of a surface****
>
>  ****
>
> How are you creating your Kinect mesh?****
>
>  ****
>
> On Fri, Apr 12, 2013 at 8:28 AM, Kilgus, Thomas <
> t.kilgus at dkfz-heidelberg.de> wrote:****
>
> Hi everyone,****
>
>  ****
>
> I’m trying to compute and render normals of certain vertices of a mesh (in
> fact a Kinect mesh). I assume that I have to compute the normals via
> vtkPolyDataNormals and display them using a vtkGlyph3d? ****
>
>  ****
>
> I observed some strange behavior which really confused me:****
>
>  ****
>
> 1.       If I create a vtkPlaneSource or load a ball from hard disc and
> compute normals for that data, everything seems fine. If I load an “open”
> surface (my Kinect mesh), there are no normals displayed. The documentation
> says that SetAutoOrientNormals does only work with closed surfaces. But at
> the moment I don’t care about orientation. There should be normals for at
> least some vertices of an open mesh, shouldn’t there?****
>
> 2.       If I load my Kinect mesh and make a new polydata which contains
> as much points at (0,0,0) as I have normals and set the normals for the new
> polydata, the glyph will produce arrows pointing from (0,0,0) to somewhere.
> This looks pretty good could but could be a random result with empty
> memory. ****
>
> 3.       If I connect my vtkPlaneSource or the ball directly to the glyph
> (I skip the vtkPolyDataNormals), normals are still rendered correctly. Does
> this mean my vtkPlaneSource already contains them from the beginning? Are
> they computed in the background somewhere inside the glyph3d? Is the
> vtkPolyDataNormals even necessary? This only works for the plane and the
> ball - not for the Kinect mesh. I can imagine that a plane automatically
> computes its normal on Update(), but why does my ball have normals already?
> ****
>
> 4.       How can I get the normal of a certain vertex Id? If I use
> vtkFloatArray::SafeDownCast(output->GetPointData()->GetNormals()) are Id’s
> equal to the vertex Id’s of the polydata? What happens if I turn splitting
> on and get multiple normals for each vertex? How is the mapping done?****
>
>  ****
>
> My code looks as follows:****
>
>  ****
>
> vtkSmartPointer<vtkPolyData> inputPolyData = //load some data****
>
>  ****
>
>   // Generate normals****
>
>   vtkSmartPointer<vtkPolyDataNormals> normalGenerator =
> vtkSmartPointer<vtkPolyDataNormals>::New();****
>
>   normalGenerator->SetInput( inputPolyData );****
>
>   normalGenerator->ComputePointNormalsOn();****
>
>   normalGenerator->ComputeCellNormalsOff();****
>
>   normalGenerator->SetSplitting(0); //I want exactly one normal per vertex
> ****
>
>   normalGenerator->Update();****
>
>  ****
>
>   vtkSmartPointer<vtkPolyDataMapper> mapperNormals =****
>
>       vtkSmartPointer<vtkPolyDataMapper>::New();****
>
>  ****
>
>   //I chose arrows as representation****
>
>   vtkSmartPointer<vtkArrowSource> arrow =
> vtkSmartPointer<vtkArrowSource>::New();****
>
>   arrow->Update();****
>
>  ****
>
> //use the output of vtkPolyDataNormals as input for the glyph3d****
>
> vtkSmartPointer<vtkGlyph3D> glyph =
> vtkSmartPointer<vtkMaskedGlyph3D>::New();****
>
>   glyph->SetInput( normalGenerator->GetOutput() );****
>
>   glyph->SetSourceConnection(arrow->GetOutputPort());****
>
>   glyph->OrientOn();****
>
>   glyph->SetVectorModeToUseNormal();****
>
>   glyph->Update();****
>
>  ****
>
>   mapperNormals->SetInputConnection(glyph->GetOutputPort());****
>
>  ****
>
> //now follows standard code which could be taken from almost any example…*
> ***
>
>   vtkSmartPointer<vtkActor> actorNormals =****
>
>       vtkSmartPointer<vtkActor>::New();****
>
>   actorNormals->SetMapper(mapperNormals);****
>
>  ****
>
>   // Create a renderer, render window, and interactor****
>
>   vtkSmartPointer<vtkRenderer> renderer =****
>
>       vtkSmartPointer<vtkRenderer>::New();****
>
>   vtkSmartPointer<vtkRenderWindow> renderWindow =****
>
>       vtkSmartPointer<vtkRenderWindow>::New();****
>
>   renderWindow->AddRenderer(renderer);****
>
>   vtkSmartPointer<vtkRenderWindowInteractor> renderWindowInteractor =****
>
>       vtkSmartPointer<vtkRenderWindowInteractor>::New();****
>
>   vtkSmartPointer<vtkInteractorStyleTrackballCamera> style =
> vtkSmartPointer<vtkInteractorStyleTrackballCamera>::New();****
>
>   renderWindowInteractor->SetInteractorStyle(style);****
>
>   renderWindowInteractor->SetRenderWindow(renderWindow);****
>
>  ****
>
>   // Add the actor to the scene****
>
>   renderer->AddActor(actorNormals);****
>
>  ****
>
>   // Render and interact****
>
>   renderWindow->Render();****
>
>   renderWindowInteractor->Start();****
>
>  ****
>
> Regards,****
>
> Thomas****
>
>  ****
>
>  ****
>
> Thomas Kilgus****
>
> German Cancer Research Center (DKFZ)****
>
> Div. Medical and Biological Informatics ****
>
> Junior group: Computer-assisted Interventions (E131)****
>
> Im Neuenheimer Feld 280****
>
> 69120 Heidelberg, Germany****
>
> Phone: +49(0) 6221-42-3545****
>
>  ****
>
>
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> ****
>
>  ****
>
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> ****
>
>  ****
>
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> ****
>
>  ****
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> ** **
>
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