# Support

**URL:** https://discourse.vtk.org/c/support/6.md?page=136

[Latest](https://discourse.vtk.org/latest.md) · [Categories](https://discourse.vtk.org/categories.md) · [Tags](https://discourse.vtk.org/tags.md)

**Page:** 137

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## [Processing ExodusII data](https://discourse.vtk.org/t/processing-exodusii-data/2885)

<div class="topic-metadata">

**Author:** [@nikhilgv](https://discourse.vtk.org/u/nikhilgv)\
**Replies:** 1\
**Last updated:** [April 1, 2020, 3:43pm UTC](https://discourse.vtk.org/t/processing-exodusii-data/2885 "2020-04-01T15:43:19Z")

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Hello, I am new to VTK. Here is what I need to do: Read exodusII file. The exodus file contains spatio-temporal data for multiple scalar variables. Choose a particular scalar variable. Apply a threshold filter to the …

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## [Problem for saving image to png](https://discourse.vtk.org/t/problem-for-saving-image-to-png/2924)

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**Author:** [@NeuZhangQiang](https://discourse.vtk.org/u/NeuZhangQiang)\
**Replies:** 4\
**Last updated:** [April 1, 2020, 10:04am UTC](https://discourse.vtk.org/t/problem-for-saving-image-to-png/2924 "2020-04-01T10:04:59Z")

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I want to save a image to png, and it is OK. However, when I read it, bug happens. The code is: vtkSmartPointer\<vtkPNGWriter\> imgWriter = vtkSmartPointer\<vtkPNGWriter\>::New(); imgWriter-\>SetInputData(img); img…

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## [self intersections from extrusion](https://discourse.vtk.org/t/self-intersections-from-extrusion/2919)

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**Author:** [@mikewho](https://discourse.vtk.org/u/mikewho)\
**Replies:** 6\
**Last updated:** [March 31, 2020, 7:52pm UTC](https://discourse.vtk.org/t/self-intersections-from-extrusion/2919 "2020-03-31T19:52:26Z")

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I’m attempting to extrude and then make a solid voxel representation of a surface in VTK. The initial surface is well-behaved, not self-intersecting. The general pipeline is vtkLinearExtrusionFilter -\> vtkPolyDatatoImage…

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## [decreasing and increasing the points in vtp file](https://discourse.vtk.org/t/decreasing-and-increasing-the-points-in-vtp-file/2902)

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**Author:** [@wal](https://discourse.vtk.org/u/wal)\
**Replies:** 5\
**Last updated:** [March 31, 2020, 6:28pm UTC](https://discourse.vtk.org/t/decreasing-and-increasing-the-points-in-vtp-file/2902 "2020-03-31T18:28:04Z")

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Hello, I am preparing data for a neural network, the input of my network will be a constant number of points with its coordinates and a scalar value. The problem with the vtp files is that they have a different number o…

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## [OpenGL state errors with QVTKOpenGLWidget and vtk8.2 on Render call](https://discourse.vtk.org/t/opengl-state-errors-with-qvtkopenglwidget-and-vtk8-2-on-render-call/2921)

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**Author:** [@tchen87](https://discourse.vtk.org/u/tchen87)\
**Replies:** 6\
**Last updated:** [March 31, 2020, 4:58pm UTC](https://discourse.vtk.org/t/opengl-state-errors-with-qvtkopenglwidget-and-vtk8-2-on-render-call/2921 "2020-03-31T16:58:54Z")

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I have an stereo application utilizing QT and running well on VTK8.1 using QVTKWidget. However, when switching to VTK8.2, I see a number of VTK errors every time a call is made to vtkRenderer::Render() Here is the stack…

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## [BMP Reader](https://discourse.vtk.org/t/bmp-reader/2878)

<div class="topic-metadata">

**Author:** [@kalpathi](https://discourse.vtk.org/u/kalpathi)\
**Replies:** 15\
**Last updated:** [March 31, 2020, 1:23pm UTC](https://discourse.vtk.org/t/bmp-reader/2878 "2020-03-31T13:23:25Z")

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I havent used VTK in decades, so bear with me. It was a lot simpler C++ in the 90s! Or I am just too old! Trying to read a series of BMP images into a volume and isosurface it. Somehow its seg faulting. So I want to l…

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## [How to show gradient of isoSurface based on color.](https://discourse.vtk.org/t/how-to-show-gradient-of-isosurface-based-on-color/2874)

<div class="topic-metadata">

**Author:** [@ShaneKirkbride](https://discourse.vtk.org/u/ShaneKirkbride)\
**Replies:** 4\
**Last updated:** [March 31, 2020, 11:24am UTC](https://discourse.vtk.org/t/how-to-show-gradient-of-isosurface-based-on-color/2874 "2020-03-31T11:24:07Z")

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I’m trying to understand how I can render an isosurface and show it’s gradient using color. There are a few examples but it is unclear how to do this with an isosurface.

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## [Does VTK have any support to order triangles on a mesh?](https://discourse.vtk.org/t/does-vtk-have-any-support-to-order-triangles-on-a-mesh/2922)

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**Author:** [@tdchen](https://discourse.vtk.org/u/tdchen)\
**Replies:** 0\
**Last updated:** [March 31, 2020, 5:04am UTC](https://discourse.vtk.org/t/does-vtk-have-any-support-to-order-triangles-on-a-mesh/2922 "2020-03-31T05:04:02Z")

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Hi vtkers. I need to make all triangles on a mesh having the same orientation, and even more to get the border of it. Does VTK have any support to this? Thank you in advance.

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## [OpenGL state errors with QVTKOpenGLWidget and vtk8.2](https://discourse.vtk.org/t/opengl-state-errors-with-qvtkopenglwidget-and-vtk8-2/539)

<div class="topic-metadata">

**Author:** [@geoffw](https://discourse.vtk.org/u/geoffw)\
**Replies:** 10\
**Last updated:** [March 31, 2020, 1:31am UTC](https://discourse.vtk.org/t/opengl-state-errors-with-qvtkopenglwidget-and-vtk8-2/539 "2020-03-31T01:31:15Z")

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Hi, We have an application based on Qt and Vtk. It runs well on VTK8.1 However, after upgrading to VTK8.2, we experience problems when we first call vtkRenderer::Render(). This call ultimately ends up calling vtkOpenGLS…

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## [isosurface related..](https://discourse.vtk.org/t/isosurface-related/2920)

<div class="topic-metadata">

**Author:** [@kalpathi](https://discourse.vtk.org/u/kalpathi)\
**Replies:** 0\
**Last updated:** [March 30, 2020, 8:34pm UTC](https://discourse.vtk.org/t/isosurface-related/2920 "2020-03-30T20:34:22Z")

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If your data is coming from a multi-component image(say a bmp with r,gb) or volume, how do y you specify the component on which to extract the isoline/isosurface?

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## [QWidget and the vtkContextView?](https://discourse.vtk.org/t/qwidget-and-the-vtkcontextview/2907)

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**Author:** [@wulicheng](https://discourse.vtk.org/u/wulicheng)\
**Replies:** 1\
**Last updated:** [March 30, 2020, 1:48am UTC](https://discourse.vtk.org/t/qwidget-and-the-vtkcontextview/2907 "2020-03-30T01:48:48Z")

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How can i integrate the vtkContextView withe the Qt’widget like QVTKＷＩｇｅｔ?

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## [vtkMarching Squares Example - dataset..](https://discourse.vtk.org/t/vtkmarching-squares-example-dataset/2897)

<div class="topic-metadata">

**Author:** [@kalpathi](https://discourse.vtk.org/u/kalpathi)\
**Replies:** 1\
**Last updated:** [March 28, 2020, 12:45pm UTC](https://discourse.vtk.org/t/vtkmarching-squares-example-dataset/2897 "2020-03-28T12:45:45Z")

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Could someone point me to the dataset (image) that was used in the following example: https://lorensen.github.io/VTKExamples/site/Cxx/Modelling/ContourTriangulator/ Or where you find datasets for many of the examples? …

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## [Plotting a bar diagram with more than 40.000 points is very slow](https://discourse.vtk.org/t/plotting-a-bar-diagram-with-more-than-40-000-points-is-very-slow/2889)

<div class="topic-metadata">

**Author:** [@MagnaBlandit](https://discourse.vtk.org/u/MagnaBlandit)\
**Replies:** 1\
**Last updated:** [March 26, 2020, 3:31pm UTC](https://discourse.vtk.org/t/plotting-a-bar-diagram-with-more-than-40-000-points-is-very-slow/2889 "2020-03-26T15:31:43Z")

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Hello, Iam trying to plot a 1D-Signal in a vtkChartXY. I have more than 40.000 points, which works fine with vtkChart.LINE and vtkChart.POINTS, but if I try to plot with vtkChart.BAR the program slows down significantl…

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## [random orientation, and location of objects in a bounding box](https://discourse.vtk.org/t/random-orientation-and-location-of-objects-in-a-bounding-box/2839)

<div class="topic-metadata">

**Author:** [@kayarre](https://discourse.vtk.org/u/kayarre)\
**Replies:** 4\
**Last updated:** [March 26, 2020, 10:35am UTC](https://discourse.vtk.org/t/random-orientation-and-location-of-objects-in-a-bounding-box/2839 "2020-03-26T10:35:41Z")

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I have a large set of PolyData shapes and I want to randomly sample from a list of them and place them in a bounded region in space, and don’t want them to overlap. They are generally the same size and all have zero orig…

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## [Surface Data on Structured Grid](https://discourse.vtk.org/t/surface-data-on-structured-grid/2887)

<div class="topic-metadata">

**Author:** [@B.S](https://discourse.vtk.org/u/B.S)\
**Replies:** 0\
**Last updated:** [March 26, 2020, 10:32am UTC](https://discourse.vtk.org/t/surface-data-on-structured-grid/2887 "2020-03-26T10:32:39Z")

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Looking for a document that discusses surface data for structured grids in detail. Any help would be appreciated. In particular, interested in visualizing surface data on the FACES of structured grid data (e.g. VTK-Hexa…

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## [vtk python wrapper problem with compilation](https://discourse.vtk.org/t/vtk-python-wrapper-problem-with-compilation/2236)

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**Author:** [@Inna\_Daymand](https://discourse.vtk.org/u/Inna_Daymand)\
**Replies:** 29\
**Last updated:** [March 25, 2020, 11:01am UTC](https://discourse.vtk.org/t/vtk-python-wrapper-problem-with-compilation/2236 "2020-03-25T11:01:03Z")

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Hi everyone, I have a problem with compilation files for wrapping there is my cmake file CMAKE\_MINIMUM\_REQUIRED(VERSION 3.3) PROJECT(vtkExamplePython) #C++11 flags set(CMAKE\_CXX\_FLAGS “${CMAKE\_CXX\_FLAGS} -Wall -std=c…

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## [undefined symbol error due to netcdf linking](https://discourse.vtk.org/t/undefined-symbol-error-due-to-netcdf-linking/2870)

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**Author:** [@hubutui](https://discourse.vtk.org/u/hubutui)\
**Replies:** 6\
**Last updated:** [March 24, 2020, 6:41pm UTC](https://discourse.vtk.org/t/undefined-symbol-error-due-to-netcdf-linking/2870 "2020-03-24T18:41:16Z")

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Hi, I build vtk from the master branch for ArchLinux with configuration: cmake .. \\ -DBUILD\_SHARED\_LIBS=ON \\ -DBUILD\_TESTING=OFF \\ -DCMAKE\_BUILD\_TYPE=Release \\ -DCMAKE\_INSTALL\_LIBDIR=lib \\ -DCMAKE\_…

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## [Get voxel intensity](https://discourse.vtk.org/t/get-voxel-intensity/2797)

<div class="topic-metadata">

**Author:** [@flaviu2](https://discourse.vtk.org/u/flaviu2)\
**Replies:** 8\
**Last updated:** [March 23, 2020, 9:06pm UTC](https://discourse.vtk.org/t/get-voxel-intensity/2797 "2020-03-23T21:06:25Z")

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I have a VC++ app that use VTK for visualizing DICOM CBCT and SimpleITK for segmentation (I intend to do segmentation, until now, it doesn’t working :slight\_smile: ) When I click on vtkVolume, I am using vtkCellPicker …

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## [How to place vtkDistanceWidget to vtkImageReslice to save it as the slice meta image](https://discourse.vtk.org/t/how-to-place-vtkdistancewidget-to-vtkimagereslice-to-save-it-as-the-slice-meta-image/2865)

<div class="topic-metadata">

**Author:** [@kimia.af1998](https://discourse.vtk.org/u/kimia.af1998)\
**Replies:** 6\
**Last updated:** [March 23, 2020, 5:32pm UTC](https://discourse.vtk.org/t/how-to-place-vtkdistancewidget-to-vtkimagereslice-to-save-it-as-the-slice-meta-image/2865 "2020-03-23T17:32:45Z")

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Hi. I created vtkDistanceWidget to measure distance on my reslice image. and it works fine but when I scroll through slices, the distanceWidget also appears.I want to display the measure tool only for current slice not …

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## [changing the color of one sphere on a vtkContourWidget](https://discourse.vtk.org/t/changing-the-color-of-one-sphere-on-a-vtkcontourwidget/2866)

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**Author:** [@Olicr](https://discourse.vtk.org/u/Olicr)\
**Replies:** 0\
**Last updated:** [March 22, 2020, 2:25pm UTC](https://discourse.vtk.org/t/changing-the-color-of-one-sphere-on-a-vtkcontourwidget/2866 "2020-03-22T14:25:14Z")

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Hello dear people, I am trying to change a specific sphere color on a vtkContourWidget. I have been searching the web before asking you, but couldn(t find any help from there. The properties I know and that I can chan…

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## [How to convert a set of contour to surface?](https://discourse.vtk.org/t/how-to-convert-a-set-of-contour-to-surface/2859)

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**Author:** [@zhang-qiang-github](https://discourse.vtk.org/u/zhang-qiang-github)\
**Replies:** 8\
**Last updated:** [March 22, 2020, 12:33am UTC](https://discourse.vtk.org/t/how-to-convert-a-set-of-contour-to-surface/2859 "2020-03-22T00:33:48Z")

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I have a set of contour, and I want to convert the contours to surface. However, the contours are not paralleled. The created surface should be a bend tube. Is there any class in VTK can implement this function?

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## [Is this the proper way to use vtkStructuredGridAppend?](https://discourse.vtk.org/t/is-this-the-proper-way-to-use-vtkstructuredgridappend/2674)

<div class="topic-metadata">

**Author:** [@kabel](https://discourse.vtk.org/u/kabel)\
**Replies:** 3\
**Last updated:** [March 21, 2020, 5:28pm UTC](https://discourse.vtk.org/t/is-this-the-proper-way-to-use-vtkstructuredgridappend/2674 "2020-03-21T17:28:27Z")

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I seem to have an issue with vtkStructuredGridAppend. I am not sure if I am doing something wrong. I have two small structured grids. Each contains scalar data and the scalar data has the same names in both files. I want…

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## [Complex Concave Polygons](https://discourse.vtk.org/t/complex-concave-polygons/2857)

<div class="topic-metadata">

**Author:** [@Gerald](https://discourse.vtk.org/u/Gerald)\
**Replies:** 7\
**Last updated:** [March 21, 2020, 4:33pm UTC](https://discourse.vtk.org/t/complex-concave-polygons/2857 "2020-03-21T16:33:54Z")

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Hi all, I am dealing with complex concave polygons. My polygons are: concave self-touching (either point/point or point/edge, edge/edge) at least once, most of the time multiple never self-intersecting aligned on a pl…

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## [EnSight reader example (C++)](https://discourse.vtk.org/t/ensight-reader-example-c/2799)

<div class="topic-metadata">

**Author:** [@floF](https://discourse.vtk.org/u/floF)\
**Replies:** 1\
**Last updated:** [March 21, 2020, 3:31pm UTC](https://discourse.vtk.org/t/ensight-reader-example-c/2799 "2020-03-21T15:31:31Z")

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Hello, I’m trying to read EnSight Gold data using the VTK library for C++. Unfortunately I didn’t find any example for this files type, and since my global knowledge in C++ is far from being perfect, I didn’t managed s…

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## [Unstructured Gradient Filter and Marching Cubes](https://discourse.vtk.org/t/unstructured-gradient-filter-and-marching-cubes/2853)

<div class="topic-metadata">

**Author:** [@ShaneKirkbride](https://discourse.vtk.org/u/ShaneKirkbride)\
**Replies:** 2\
**Last updated:** [March 20, 2020, 5:00pm UTC](https://discourse.vtk.org/t/unstructured-gradient-filter-and-marching-cubes/2853 "2020-03-20T17:00:25Z")

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I’m trying to show the gradient of a polyData surface similiar to the marching cubes example: https://lorensen.github.io/VTKExamples/site/Cxx/Modelling/MarchingCubes/ I read in the documentation: https://vtk.org/doc/n…

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## [VTK9.0 RC1: vtkScalarBarActorInternal.h not installed](https://discourse.vtk.org/t/vtk9-0-rc1-vtkscalarbaractorinternal-h-not-installed/2855)

<div class="topic-metadata">

**Author:** [@lukas](https://discourse.vtk.org/u/lukas)\
**Replies:** 1\
**Last updated:** [March 20, 2020, 1:02pm UTC](https://discourse.vtk.org/t/vtk9-0-rc1-vtkscalarbaractorinternal-h-not-installed/2855 "2020-03-20T13:02:42Z")

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Hi all, I have a problem with the vtkScalarBarActor in RC1 of VTK9.0. I am working with VTK libraries installed with ninja install. With VTK8.2 I am able to create a subclass of vtkScalarBarActor and access the pointer…

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## [python 3.8 wheel on Mac OS X](https://discourse.vtk.org/t/python-3-8-wheel-on-mac-os-x/2850)

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**Author:** [@noam.bern](https://discourse.vtk.org/u/noam.bern)\
**Replies:** 9\
**Last updated:** [March 19, 2020, 6:18pm UTC](https://discourse.vtk.org/t/python-3-8-wheel-on-mac-os-x/2850 "2020-03-19T18:18:04Z")

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Hi - I’ve been trying to figure out how to get vtk to work with python 3.8, and in particular in making a wheel for easy installation. The basic vtk functionality works when compiling from source (using the patch from h…

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## [Texture Mapping a Tube Uniformly](https://discourse.vtk.org/t/texture-mapping-a-tube-uniformly/2854)

<div class="topic-metadata">

**Author:** [@TravStu22](https://discourse.vtk.org/u/TravStu22)\
**Replies:** 0\
**Last updated:** [March 19, 2020, 2:27pm UTC](https://discourse.vtk.org/t/texture-mapping-a-tube-uniformly/2854 "2020-03-19T14:27:51Z")

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Hi, when trying to texture map a tube, I see the first strip gets the full texture and the rest of the strips get the full texture again stretched amongst them. I would like the texture to be applied evenly along all the…

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## [File not found when running iOS examples](https://discourse.vtk.org/t/file-not-found-when-running-ios-examples/829)

<div class="topic-metadata">

**Author:** [@vsaase](https://discourse.vtk.org/u/vsaase)\
**Replies:** 1\
**Last updated:** [March 19, 2020, 2:26am UTC](https://discourse.vtk.org/t/file-not-found-when-running-ios-examples/829 "2020-03-19T02:26:15Z")

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Hi, total VTK newbie here, I am trying to run one of the iOS examples but get stuck here: #include “vtk/vtkRenderingOpenGL2ObjectFactory.h” is not found, which seems to only be used by iOS examples, and only in this li…

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## [How do I color image data by its associated cell data?](https://discourse.vtk.org/t/how-do-i-color-image-data-by-its-associated-cell-data/2840)

<div class="topic-metadata">

**Author:** [@kevins](https://discourse.vtk.org/u/kevins)\
**Replies:** 9\
**Last updated:** [March 18, 2020, 2:46pm UTC](https://discourse.vtk.org/t/how-do-i-color-image-data-by-its-associated-cell-data/2840 "2020-03-18T14:46:44Z")

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I am using a the vtkXMLImageDataReader to load in my existing vti files that have cell data. I can load in the data just fine and display the first cell data scalar available in the file. What I am having trouble with is…

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