# How to view the boundary of a set
**URL:** https://discourse.paraview.org/t/how-to-view-the-boundary-of-a-set/1690
**Category:** ParaView Support
**Created:** [April 17, 2019, 8:42pm UTC](https://discourse.paraview.org/t/how-to-view-the-boundary-of-a-set/1690 "2019-04-17T20:42:25Z")
**Posts on this page:** 2
**Page:** 1
### Author:  [@stephen](https://discourse.paraview.org/u/stephen)
#### Post date: [April 17, 2019, 8:42pm UTC](https://discourse.paraview.org/t/how-to-view-the-boundary-of-a-set/1690/1 "2019-04-17T20:42:25Z")
I have defined a set in 3D space as a structured grid, where the value in each cell is either 0 or 1. I would like to view the boundary of this set. So I use the Contour filter. But this gives a very bumpy boundary, and I would like to smooth it out.
For example, suppose the set is a sphere. So there cell takes the value 1 if x^2+y^2+z^2 \< 9, and takes the value 0 otherwise. You would think that the a contour at the value 0.5 would give a good rendition of a sphere. But paraview will give a “lego” style rendition, because it doesn’t know that this is not what I want.
Are there any filters that can help me in this regard? I am very new to paraview, so this may be a very standard question. But I don’t even know which keywords to feed into google.
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### Author:  [@nicolas.vuaille](https://discourse.paraview.org/u/nicolas.vuaille)
#### Post date: [April 25, 2019, 2:18pm UTC](https://discourse.paraview.org/t/how-to-view-the-boundary-of-a-set/1690/2 "2019-04-25T14:18:31Z")
As you work with cell data, you extract cells and see cells as they are in a structured grid, i.e as ‘lego’.
You may want to work with point data so the extraction will extract points and recompute surface to have a smooth render.
You can easily test by using CellDataToPointData filter before extracting the boundary.