# How to extract surface from polydata

**URL:** https://discourse.vtk.org/t/how-to-extract-surface-from-polydata/321
**Category:** Support
**Created:** [February 25, 2019, 11:14am UTC](https://discourse.vtk.org/t/how-to-extract-surface-from-polydata/321 "2019-02-25T11:14:54Z")
**Posts on this page:** 1
**Showing post:** 11

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### Author: ![mwestphal](https://discourse.vtk.org/user_avatar/discourse.vtk.org/mwestphal/32/19_2.png) [@mwestphal](https://discourse.vtk.org/u/mwestphal)
#### Post date: [August 5, 2019, 3:00pm UTC](https://discourse.vtk.org/t/how-to-extract-surface-from-polydata/321/11 "2019-08-05T15:00:49Z")

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@at123 : please avoid asking the same question in multiple posts.

> [@Problems using vtkContourWidget, vtkAppendPolyData, and vtkDelaunay3D](https://discourse.vtk.org/t/problems-using-vtkcontourwidget-vtkappendpolydata-and-vtkdelaunay3d/1480):
>
> Hello, I have a ImageResliceVTKWidget. I can move across a series of medical images. Say I am moving from left to right between images. To create a contour on a certain image, I use the vtkContourWidget. I click multiple points and create a closed loop. First I create a large circle, then move to the right. Then I create a smaller circle. Then move to the right. Then create a large circle again. I would like to create a volume using these contours. So I use the vtkAppendPolyData. I do someth…

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