# Normal at Surface in 3D cube

**URL:** <https://community.freefem.org/t/normal-at-surface-in-3d-cube/1203>\
**Category:** General Discussion\
**Created:** [September 14, 2021, 7:38am UTC](https://community.freefem.org/t/normal-at-surface-in-3d-cube/1203 "2021-09-14T07:38:24Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![sumantkr](https://yyz2.discourse-cdn.com/flex030/user_avatar/community.freefem.org/sumantkr/32/2681_2.png) [@sumantkr](https://community.freefem.org/u/sumantkr)\
**Post date:** [September 14, 2021, 7:38am UTC](https://community.freefem.org/t/normal-at-surface-in-3d-cube/1203/1 "2021-09-14T07:38:24Z")

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Dear All  
How can I access the surface boundary of the cube and normal at that Surface?

is it ok to express normal as “N = (N.x, N.y, N.Z)” .