[vtkusers] How to color a sphere source in an appendpolydata object?

[Rishi Rawat]

THANKS,
this helped me a lot

On Fri, Jan 29, 2016 at 11:55 AM, Cory Quammen <cory.quammen at kitware.com>
wrote:

> Hi Rishi,
>
> Answers inlined below:
>
> On Fri, Jan 29, 2016 at 1:04 PM, Rishi Rawat <rishiraw at usc.edu> wrote:
>
>> How to color a sphere source in an appendpolydata object?
>>
>> Eventually, I want to plot hundreds+ spheres in 3D, each with a different
>> color. I'd like to use an appendpolydata object to improve efficiency.
>> Below is the code I have so far using 1 sphere.
>>
>> I think I've tracked the problem down to the appendData object. doing
>> appendData.AddInputData(polydata sp ) causes nothing to show up in my
>> renderwindow, whereas if I do appendData.AddInputConnection(Sphere.GetOutputPort()
>> ), I get an object to show up, but it is gray (no color).
>>
>> How can I color objects before placing them in the appendpolydata object?
>>
>
> VTK doesn't quite work that way, but you are close. See my notes below.
>
>
>> My Code:
>>
>>
>> import vtk
>> from vtk import *
>> # create a rendering window and renderer
>> ren = vtk.vtkRenderer()
>> renWin = vtk.vtkRenderWindow()
>> renWin.AddRenderer(ren)
>>
>> # create a renderwindowinteractor
>> iren = vtk.vtkRenderWindowInteractor()
>> iren.SetRenderWindow(renWin)
>>
>> #setup colors (setting the name to "Colors" is nice but not necessary)
>> Colors = vtk.vtkUnsignedCharArray();
>> Colors.SetNumberOfComponents(3);
>> Colors.SetName("Colors");
>> Colors.InsertNextTuple3(255,0,0);
>>
>
> You'll need a color for *each* cell in in each sphere that you are
> appending together. You'll need a call to
>
> Colors.SetNumberOfTuples()
>
> after Colors.SetNumberOfComponents(3) and pass it the number of cells in
> the sphere source. Then, you'll need to duplicate the color by calling
>
> Colors.InsertNextTuple3()
>
> once for each cell. You can actually use
>
> color = [255, 0, 0]
> Colors.SetTupleValue(i, color)
>
> where i is the cell index because you have already allocated the array
> when you called Colors.SetNumberOfTuples().
>
>
>> sphere = vtk.vtkSphereSource()
>> sphere.SetThetaResolution(5)
>> sphere.SetPhiResolution(5)
>> sphere.SetRadius(10)
>> sphere.SetCenter( 0,0,0)
>> sp = sphere.GetOutput()
>>
>
> You'll need a call to 'sphere.Update()' here so that the output is
> generated, otherwise 'sp' will be empty and you'll be appending a lot of
> empty data sets.
>
>
>> sp.GetCellData().SetScalars(Colors);
>> appendData.AddInputData(sp )
>>
>>
>> # If I enable this next line, i get a sphere, but it is not colored, it
>> is gray
>> #appendData.AddInputConnection(sphere.GetOutputPort() )
>>
>> print "done"
>> #cd.SetScalars(Colors)
>> #cd.Update()
>> #sphere.Update()
>>
>> mapper = vtk.vtkPolyDataMapper()
>> if vtk.VTK_MAJOR_VERSION <= 5:
>>     mapper.SetInput(trianglePolyData)
>> else:
>>     #mapper.SetInputData(trianglePolyData)
>>     mapper.SetInputConnection(appendData.GetOutputPort() )
>> # actor
>> actor = vtk.vtkActor()
>> actor.SetMapper(mapper)
>>
>
> You'll also need to call
>
> mapper.SetColorModeToDirectScalars()
>
> to ensure that your spheres are colored by the colors you set in the cell
> data array rather than being mapped through a color map.
>
> HTH,
> Cory
>
>
>>
>> # assign actor to the renderer
>> ren.AddActor(actor)
>>
>> # enable user interface interactor
>> iren.Initialize()
>> renWin.Render()
>> iren.Start()
>>
>>
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>
>
> --
> Cory Quammen
> R&D Engineer
> Kitware, Inc.
>



-- 
Rishi Rawat
MD/PHD Candidate
HTE (Health Technology Engineering) Fellow
Keck School of Medicine
University of Southern California
rishiraw at usc.edu  |  720-352-6218
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