# Color specific mesh elements

**URL:** https://discourse.vtk.org/t/color-specific-mesh-elements/1447
**Category:** Support
**Created:** [July 30, 2019, 11:17am UTC](https://discourse.vtk.org/t/color-specific-mesh-elements/1447 "2019-07-30T11:17:52Z")
**Posts on this page:** 4
**Page:** 1

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### Author: ![anon64829896](https://discourse.vtk.org/letter_avatar_proxy/v4/letter/a/91b2a8/32.png) [@anon64829896](https://discourse.vtk.org/u/anon64829896)
#### Post date: [July 30, 2019, 11:17am UTC](https://discourse.vtk.org/t/color-specific-mesh-elements/1447/1 "2019-07-30T11:17:52Z")

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Hi!  
I want to plot my STL-Model (or general 3D object) using VTK. For this, I used the STLReader.  
My next step is to give some facets of the model different colors, so e.g.:  
Face 1-10 shall be red  
Face 11 - 20 shall be blue.

Since I am relatively new to VTK and the intellisense of my IDE is not giving me further interesting options, it’s hard for me to achieve this task.  
I read a lot about color lookup tables and scalararrays which are applied to the mapper but somehow, all I’ve done so far does not work.  
I am using Python for VTK.

Can somebody help me here?

Best regards  
Benny

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### Author: ![lorensen](https://discourse.vtk.org/user_avatar/discourse.vtk.org/lorensen/32/20_2.png) [@lorensen](https://discourse.vtk.org/u/lorensen)
#### Post date: [July 30, 2019, 2:55pm UTC](https://discourse.vtk.org/t/color-specific-mesh-elements/1447/2 "2019-07-30T14:55:39Z")

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Benny,

These examples from the [VTK Examples Project](https://lorensen.github.io/VTKExamples/site/.). may help. They coth color individual cells.

1. [ColorCells](https://lorensen.github.io/VTKExamples/site/Cxx/PolyData/ColorCells/)
2. [ColorCellsWithRGB](https://lorensen.github.io/VTKExamples/site/Cxx/PolyData/ColorCellsWithRGB/)

Enjoy VTK,

Bill

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### Author: ![marcomusy](https://discourse.vtk.org/user_avatar/discourse.vtk.org/marcomusy/32/95_2.png) [@marcomusy](https://discourse.vtk.org/u/marcomusy)
#### Post date: [July 31, 2019, 11:56pm UTC](https://discourse.vtk.org/t/color-specific-mesh-elements/1447/3 "2019-07-31T23:56:29Z")

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With vtkplotter helper module:

```python
from vtkplotter import *

s = load(datadir+'shuttle.stl')

cols, als = [], []
for i in range(s.NCells()):
    cols.append(i) # i-th color
    als.append(i/s.NCells()) #opacity

s.colorCellsByArray(cols, als).lw(1).show()

```

![Screenshot%20from%202019-08-01%2001-42-12](https://discourse.vtk.org/uploads/default/original/1X/2e27b6346a18e3fd6c749f75307e06b95fe33f85.png)

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<div class="post-metadata">

### Author: ![anon64829896](https://discourse.vtk.org/letter_avatar_proxy/v4/letter/a/91b2a8/32.png) [@anon64829896](https://discourse.vtk.org/u/anon64829896)
#### Post date: [August 7, 2019, 11:11am UTC](https://discourse.vtk.org/t/color-specific-mesh-elements/1447/4 "2019-08-07T11:11:36Z")

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Thanks for your answers, I solved the problem using following exemplary code:

> reader = vtkOFFReader()  
> reader.SetFileName(meshfile)
> 
> vtkpolydata = reader.GetPolyData()  
> scalarArray = numpy\_support.numpy\_to\_vtk(scalararray)
> 
> vtkpolydata.GetCellData().SetScalars(scalarArray)
> 
> lut = vtk.vtkLookupTable()  
> lut.SetNumberOfTableValues(len(labels.Categories))  
> lut.SetTableRange(0,len(labels.Categories)-1)  
> lut.SetHueRange(0.2,0.667);  
> lut.Build()