[vtkusers] polyhedron in python

[Tim Hutton]

Hello,

We generate polyhedral cells as part of Ready. Some C++ code here:
https://code.google.com/p/reaction-diffusion/source/browse/trunk/Ready/src/readybase/MeshGenerators.cpp#738

Tim

On 11 September 2014 17:08, Meehan, Bernard <MEEHANBT at nv.doe.gov> wrote:

> I thought I could fix it for you - but there is a bug in my program. You
> need to write out a vtkUnstructuredGrid rather than a vtkPolyData if you
> wanted to be able to select the polyhedron as a cell. I hadn't worked with
> those before, so I figured that I would give it a shot. I think that the
> face stream is wrong ... which is why no faces show up in ParaVew. You can
> see the points with a glyph filter, but the facets don't show up. Anyone
> out there have an idea of where I went wrong? (modified version of old
> code below)
>
> # I am using VTK 6.1.0
> import vtk
> # This is a Rhombic Dodecahedron.
>
> # First, you need to store the vertex locations.
> vertex_locations = vtk.vtkPoints()
> vertex_locations.SetNumberOfPoints(14)
> vertex_locations.SetPoint( 0, (-0.816497, -0.816497,  0.00000))
> vertex_locations.SetPoint( 1, (-0.816497,  0.000000, -0.57735))
> vertex_locations.SetPoint( 2, (-0.816497,  0.000000,  0.57735))
> vertex_locations.SetPoint( 3, (-0.816497,  0.816497,  0.00000))
> vertex_locations.SetPoint( 4, ( 0.000000, -0.816497, -0.57735))
> vertex_locations.SetPoint( 5, ( 0.000000, -0.816497,  0.57735))
> vertex_locations.SetPoint( 6, ( 0.000000,  0.000000, -1.15470))
> vertex_locations.SetPoint( 7, ( 0.000000,  0.000000,  1.15470))
> vertex_locations.SetPoint( 8, ( 0.000000,  0.816497, -0.57735))
> vertex_locations.SetPoint( 9, ( 0.000000,  0.816497,  0.57735))
> vertex_locations.SetPoint(10, ( 0.816497, -0.816497,  0.00000))
> vertex_locations.SetPoint(11, ( 0.816497,  0.000000, -0.57735))
> vertex_locations.SetPoint(12, ( 0.816497,  0.000000,  0.57735))
> vertex_locations.SetPoint(13, ( 0.816497,  0.816497,  0.00000))
>
> # Next, you describe the polygons that represent the faces using the vertex
> # indices in the vtkPoints that stores the vertex locations. There are a
> number
> # of ways to do this that you can find in examples on the Wiki.
>
> polygon_faces = vtk.vtkCellArray()
>
> q = vtk.vtkQuad()
> q.GetPointIds().SetId(0,  7)
> q.GetPointIds().SetId(1, 12)
> q.GetPointIds().SetId(2, 10)
> q.GetPointIds().SetId(3,  5)
> polygon_faces.InsertNextCell(q)
>
> q = vtk.vtkQuad()
> q.GetPointIds().SetId(0,  7)
> q.GetPointIds().SetId(1, 12)
> q.GetPointIds().SetId(2, 13)
> q.GetPointIds().SetId(3,  9)
> polygon_faces.InsertNextCell(q)
>
> q = vtk.vtkQuad()
> q.GetPointIds().SetId(0,  7)
> q.GetPointIds().SetId(1,  9)
> q.GetPointIds().SetId(2,  3)
> q.GetPointIds().SetId(3,  2)
> polygon_faces.InsertNextCell(q)
>
> q = vtk.vtkQuad()
> q.GetPointIds().SetId(0,  7)
> q.GetPointIds().SetId(1,  2)
> q.GetPointIds().SetId(2,  0)
> q.GetPointIds().SetId(3,  5)
> polygon_faces.InsertNextCell(q)
>
> q = vtk.vtkQuad()
> q.GetPointIds().SetId(0,  6)
> q.GetPointIds().SetId(1, 11)
> q.GetPointIds().SetId(2, 10)
> q.GetPointIds().SetId(3,  4)
> polygon_faces.InsertNextCell(q)
>
> q = vtk.vtkQuad()
> q.GetPointIds().SetId(0,  6)
> q.GetPointIds().SetId(1,  4)
> q.GetPointIds().SetId(2,  0)
> q.GetPointIds().SetId(3,  1)
> polygon_faces.InsertNextCell(q)
>
> q = vtk.vtkQuad()
> q.GetPointIds().SetId(0,  6)
> q.GetPointIds().SetId(1,  1)
> q.GetPointIds().SetId(2,  3)
> q.GetPointIds().SetId(3,  8)
> polygon_faces.InsertNextCell(q)
>
> q = vtk.vtkQuad()
> q.GetPointIds().SetId(0,  6)
> q.GetPointIds().SetId(1,  8)
> q.GetPointIds().SetId(2, 13)
> q.GetPointIds().SetId(3, 11)
> polygon_faces.InsertNextCell(q)
>
> q = vtk.vtkQuad()
> q.GetPointIds().SetId(0, 10)
> q.GetPointIds().SetId(1, 11)
> q.GetPointIds().SetId(2, 13)
> q.GetPointIds().SetId(3, 12)
> polygon_faces.InsertNextCell(q)
>
> q = vtk.vtkQuad()
> q.GetPointIds().SetId(0, 13)
> q.GetPointIds().SetId(1,  8)
> q.GetPointIds().SetId(2,  3)
> q.GetPointIds().SetId(3,  9)
> polygon_faces.InsertNextCell(q)
>
> q = vtk.vtkQuad()
> q.GetPointIds().SetId(0,  3)
> q.GetPointIds().SetId(1,  1)
> q.GetPointIds().SetId(2,  0)
> q.GetPointIds().SetId(3,  2)
> polygon_faces.InsertNextCell(q)
>
> q = vtk.vtkQuad()
> q.GetPointIds().SetId(0,  0)
> q.GetPointIds().SetId(1,  4)
> q.GetPointIds().SetId(2, 10)
> q.GetPointIds().SetId(3,  5)
> polygon_faces.InsertNextCell(q)
>
> # Next you create a vtkPolyData to store your face and vertex information
> that
> # represents your polyhedron.
> pd = vtk.vtkPolyData()
> pd.SetPoints(vertex_locations)
> pd.SetPolys(polygon_faces)
>
> # If you wanted to be able to load in the saved file and select the entire
> # polyhedron, you would need to save it as a vtkUnstructuredGrid, and you
> would
> # need to put the data into a vtkPolyhedron. This is a bit more involved
> than
> # the vtkPolyData that I used above. For a more in-depth discussion, see:
> # http://www.vtk.org/Wiki/VTK/Polyhedron_Support
>
> # Based on the link above, I need to construct a face stream:
> face_stream = vtk.vtkIdList()
> face_stream.InsertNextId(polygon_faces.GetNumberOfCells())
> vertex_list = vtk.vtkIdList()
>
> polygon_faces.InitTraversal()
> while polygon_faces.GetNextCell(vertex_list) == 1:
>
>   face_stream.InsertNextId(vertex_list.GetNumberOfIds())
>
>   for j in range(vertex_list.GetNumberOfIds()):
>     face_stream.InsertNextId(vertex_list.GetId(j))
>
> ug = vtk.vtkUnstructuredGrid()
> ug.SetPoints(vertex_locations)
> ug.InsertNextCell(vtk.VTK_POLYHEDRON, face_stream)
>
> #--------------#
> # output stuff #
> #--------------#
> writer = vtk.vtkUnstructuredGridWriter()
> writer.SetFileName("rhombic_dodecahedron.vtk")
> writer.SetInputData(ug)
> writer.Write()
>
> #---------------------#
> # visualization stuff #
> #---------------------#
> # mapper = vtk.vtkPolyDataMapper()
> # mapper.SetInputData(pd)
> mapper = vtk.vtkDataSetMapper()
> mapper.SetInputData(ug)
>
> actor = vtk.vtkActor()
> actor.SetMapper(mapper)
>
> ren = vtk.vtkRenderer()
> ren.AddActor(actor)
>
> renw = vtk.vtkRenderWindow()
> renw.AddRenderer(ren)
>
> iren = vtk.vtkRenderWindowInteractor()
> iren.SetRenderWindow(renw)
>
> ren.ResetCamera()
> renw.Render()
> iren.Start()
>
>
> On 9/10/14 2:34 PM, "George" <george.gerber at gmail.com> wrote:
>
> >Hi,
> >The example of Meehan works quite well.
> >However, I see that each face of the polyhedron is listed as a cell. Is it
> >possible to hide these face 'cells', so that when you select the
> >polyhedron
> >in paraview it lists only 1 cell (the polyhedron itself)?
> >
> >Best regards,
> >George
> >
> >
> >
> >--
> >View this message in context:
> >
> http://vtk.1045678.n5.nabble.com/polyhedron-in-python-tp5728643p5728664.ht
> >ml
> >Sent from the VTK - Users mailing list archive at Nabble.com.
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-- 
Tim Hutton - http://www.sq3.org.uk - http://profiles.google.com/tim.hutton/
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