# Surface of high-order DG function includes internal surfaces

**URL:** https://discourse.paraview.org/t/surface-of-high-order-dg-function-includes-internal-surfaces/12573
**Category:** ParaView Support
**Created:** [July 24, 2023, 2:40pm UTC](https://discourse.paraview.org/t/surface-of-high-order-dg-function-includes-internal-surfaces/12573 "2023-07-24T14:40:46Z")
**Posts on this page:** 1
**Page:** 1

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### Author: ![Massimiliano\_Leoni](https://discourse.paraview.org/user_avatar/discourse.paraview.org/massimiliano_leoni/32/376_2.png) [@Massimiliano\_Leoni](https://discourse.paraview.org/u/Massimiliano_Leoni)
#### Post date: [July 24, 2023, 2:40pm UTC](https://discourse.paraview.org/t/surface-of-high-order-dg-function-includes-internal-surfaces/12573/1 "2023-07-24T14:40:46Z")

</div>

I have been saving some functions as discontinuous linear or quadratic functions and while postprocessing I realised that the mesh “surfaces” include the facets, aka the boundaries between cells.  
For example in the screenshot below

 ![internalSurfaces](https://discourse.paraview.org/uploads/default/original/2X/b/bf8d309c05654e77c32a3181c586e2120ef556de.jpeg)

you can see that the `ExtractSurface` filter, on the right, keeps the boundaries between cells.

This makes it very hard to visualise data sometimes, is there a way to fix this? Should I file a bug report?

Example data:  
[uL.zip](https://discourse.paraview.org/uploads/short-url/48ST5CRnI8aalTtCRGul078lMiR.zip) (9.2 KB)

This topic is similar to [Opacity for high order function](https://discourse.paraview.org/t/opacity-for-high-order-function/10499) with the exception that I don’t have this problem with continuous functions, only with discontinuous functions.