# How to get normal vectors on slices?

**URL:** https://discourse.vtk.org/t/how-to-get-normal-vectors-on-slices/4011
**Category:** Support
**Created:** [August 18, 2020, 11:21am UTC](https://discourse.vtk.org/t/how-to-get-normal-vectors-on-slices/4011 "2020-08-18T11:21:10Z")
**Posts on this page:** 1
**Page:** 1

<div class="post-metadata">

### Author: ![Yusuf\_Demiroglu](https://discourse.vtk.org/user_avatar/discourse.vtk.org/yusuf_demiroglu/32/2190_2.png) [@Yusuf\_Demiroglu](https://discourse.vtk.org/u/Yusuf_Demiroglu)
#### Post date: [August 18, 2020, 11:21am UTC](https://discourse.vtk.org/t/how-to-get-normal-vectors-on-slices/4011/1 "2020-08-18T11:21:10Z")

</div>

Hi everyone,

I am trying to find forces on a slice that taken over a surface and the total closed area in this slice. I got some scalar quantities over the surface. I need normal vectors to be multiplied to get forces.

I can obtain normal vectors on surface and I can obtain these scalar variables on the slice. However, I couldn’t get normal vectors on the slice. I think an interpolation is needed.

My question is that is there any command I can use to interpolate these surface normal vectors to the slice. If there is no such a command, can you suggest any way to do that?

I am using vtk library in python and I used cutter command to obtain a slice. Thank you for your answers.