# Direction toward the inside boundary of a surface?

**URL:** <https://forum.dynamobim.com/t/direction-toward-the-inside-boundary-of-a-surface/18342>\
**Category:** Geometry\
**Created:** [January 19, 2018, 9:15pm UTC](https://forum.dynamobim.com/t/direction-toward-the-inside-boundary-of-a-surface/18342 "2018-01-19T21:15:28Z")\
**Posts on this page:** 6\
**Page:** 1

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**Author:** ![glenncai](https://avatars.discourse-cdn.com/v4/letter/g/dc4da7/32.png) [@glenncai](https://forum.dynamobim.com/u/glenncai)\
**Post date:** [January 19, 2018, 9:15pm UTC](https://forum.dynamobim.com/t/direction-toward-the-inside-boundary-of-a-surface/18342/1 "2018-01-19T21:15:28Z")

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Is there any node that allows me to always get the direction toward the inside boundary of a surface or a close loop? Thanks

 ![offset direction](https://us1.discourse-cdn.com/flex022/uploads/dynamobim/original/3X/f/6/f6fb3147bd70e38c4e4675db7f5793b3798dd929.JPG)

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**Author:** ![Tomasz](https://sea2.discourse-cdn.com/flex022/user_avatar/forum.dynamobim.com/tomasz/32/66785_2.png) [@Tomasz](https://forum.dynamobim.com/u/Tomasz)\
**Post date:** [January 20, 2018, 12:53am UTC](https://forum.dynamobim.com/t/direction-toward-the-inside-boundary-of-a-surface/18342/2 "2018-01-20T00:53:24Z")

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Offsetting closed PolyCurve with negative value should move lines inside the shape.  
 ![Capture3](https://us1.discourse-cdn.com/flex022/uploads/dynamobim/original/3X/7/8/781d956b92917bad5ed651230ee12a2f665dffb3.png)  
If this somehow fails - you can offset face perimeter in both directions and take the smaller one.

 ![Capture5](https://us1.discourse-cdn.com/flex022/uploads/dynamobim/original/3X/b/2/b23373db0ca582591004da0ff27aa845924af97a.png)

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**Author:** ![glenncai](https://avatars.discourse-cdn.com/v4/letter/g/dc4da7/32.png) [@glenncai](https://forum.dynamobim.com/u/glenncai)\
**Post date:** [January 23, 2018, 1:49am UTC](https://forum.dynamobim.com/t/direction-toward-the-inside-boundary-of-a-surface/18342/3 "2018-01-23T01:49:42Z")

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Thanks for your reply Tomasz  
Yes, input a negative number works, but it only work when offset the close loop. but what about just offset the edge I picked?

 ![edge offset select edge](https://us1.discourse-cdn.com/flex022/uploads/dynamobim/original/3X/b/7/b75e60b4a106d15702c5f3b18aa64a3047fd5e8e.JPG)  
 ![EDGE OFFSET RESULT](https://us1.discourse-cdn.com/flex022/uploads/dynamobim/original/3X/a/3/a3b3f36559e778cb6f60f889d1fc7fd9ff6aa452.JPG)

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**Author:** ![Dimitar\_Venkov](https://sea2.discourse-cdn.com/flex022/user_avatar/forum.dynamobim.com/dimitar_venkov/32/2068_2.png) [@Dimitar\_Venkov](https://forum.dynamobim.com/u/Dimitar_Venkov)\
**Post date:** [January 23, 2018, 8:42am UTC](https://forum.dynamobim.com/t/direction-toward-the-inside-boundary-of-a-surface/18342/4 "2018-01-23T08:42:21Z")

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Offsetting lines tends to be very inconsistent. The below example is not very straight-forward but the Geometry.Translate node seems to be she surest way:

 ![image](https://us1.discourse-cdn.com/flex022/uploads/dynamobim/original/3X/0/c/0c6d56268021d4df805da7081aaf00e2b266b7b7.png)

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**Author:** ![Tomasz](https://sea2.discourse-cdn.com/flex022/user_avatar/forum.dynamobim.com/tomasz/32/66785_2.png) [@Tomasz](https://forum.dynamobim.com/u/Tomasz)\
**Post date:** [January 23, 2018, 1:17pm UTC](https://forum.dynamobim.com/t/direction-toward-the-inside-boundary-of-a-surface/18342/5 "2018-01-23T13:17:52Z")

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Something like this?

 ![Capture](https://us1.discourse-cdn.com/flex022/uploads/dynamobim/original/3X/3/2/32c83ce8892ea8701fcba9cd7fcde076d5c83cd5.png)  
 ![Project1](https://us1.discourse-cdn.com/flex022/uploads/dynamobim/original/3X/5/d/5dc18fcb34f0b7d1cc04847e684a8104bde026d0.jpg)

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<div class="post-metadata">

**Author:** ![glenncai](https://avatars.discourse-cdn.com/v4/letter/g/dc4da7/32.png) [@glenncai](https://forum.dynamobim.com/u/glenncai)\
**Post date:** [January 23, 2018, 6:11pm UTC](https://forum.dynamobim.com/t/direction-toward-the-inside-boundary-of-a-surface/18342/6 "2018-01-23T18:11:27Z")

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This is Awesome 👍