# The problem of render a vtk file

**URL:** https://discourse.vtk.org/t/the-problem-of-render-a-vtk-file/12183
**Category:** Support
**Created:** [August 23, 2023, 5:54am UTC](https://discourse.vtk.org/t/the-problem-of-render-a-vtk-file/12183 "2023-08-23T05:54:31Z")
**Posts on this page:** 3
**Page:** 1

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### Author: ![supersteven](https://discourse.vtk.org/user_avatar/discourse.vtk.org/supersteven/32/5986_2.png) [@supersteven](https://discourse.vtk.org/u/supersteven)
#### Post date: [August 23, 2023, 5:54am UTC](https://discourse.vtk.org/t/the-problem-of-render-a-vtk-file/12183/1 "2023-08-23T05:54:31Z")

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Here is a rendering of a vtk file as in attackment.  
Why some area is black?

 ![image](https://discourse.vtk.org/uploads/default/original/2X/e/eb802e2f02221ee514a1fc0396c36d732df27dac.jpeg)

[vessel2.vtk](https://discourse.vtk.org/uploads/short-url/wI6yrG5Y0uswft72WRVwaw10rzq.vtk) (2.6 MB)

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### Author: ![danlipsa](https://discourse.vtk.org/user_avatar/discourse.vtk.org/danlipsa/32/390_2.png) [@danlipsa](https://discourse.vtk.org/u/danlipsa)
#### Post date: [August 23, 2023, 2:47pm UTC](https://discourse.vtk.org/t/the-problem-of-render-a-vtk-file/12183/2 "2023-08-23T14:47:05Z")

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Your normals are pointing inwards for certain surfaces. You can use GenerateSurfaceNormals to generate new correct normals (pointing outward).

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<div class="post-metadata">

### Author: ![supersteven](https://discourse.vtk.org/user_avatar/discourse.vtk.org/supersteven/32/5986_2.png) [@supersteven](https://discourse.vtk.org/u/supersteven)
#### Post date: [August 24, 2023, 2:00am UTC](https://discourse.vtk.org/t/the-problem-of-render-a-vtk-file/12183/3 "2023-08-24T02:00:36Z")

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> [@danlipsa](#):
>
> GenerateSurfaceNormals

Thanks, you are right 👍