# Create bisector plane of two intersecting surfaces (solved)

**URL:** <https://discourse.mcneel.com/t/create-bisector-plane-of-two-intersecting-surfaces-solved/129907>\
**Category:** Rhino Developer\
**Tags:** mac, python\
**Created:** [September 8, 2021, 2:44pm UTC](https://discourse.mcneel.com/t/create-bisector-plane-of-two-intersecting-surfaces-solved/129907 "2021-09-08T14:44:40Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![leonardruven](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/leonardruven/32/652016_2.png) [@leonardruven](https://discourse.mcneel.com/u/leonardruven)\
**Post date:** [September 8, 2021, 2:44pm UTC](https://discourse.mcneel.com/t/create-bisector-plane-of-two-intersecting-surfaces-solved/129907/1 "2021-09-08T14:44:40Z")

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Hi Forum,

I am quite new to scripting and working on a little python script to find the bisector surface of two intersecting surfaces.

I have a polysurface with triangle faces. Each edge has an intersection. The direction of all faces is the same. That means no one is flipped.

I want to create a surface which is in the bisector of the two neighbors. Like the red surface in the following screenshot (modeled in Rhino)

 ![image](https://global.discourse-cdn.com/mcneel/uploads/default/original/4X/6/f/4/6f4327fa2fad0053cf7c7e5cdbcfbf23bc7bd854.png)

I made a python script but I think I make a mistake creating the right vector for the bisector surface.

[BisectorPlane.py](https://discourse.mcneel.com/uploads/short-url/p6VnmZVlJ14XdWrOfmE0gfMycRm.py) (1.9 KB)

 ![image](https://global.discourse-cdn.com/mcneel/uploads/default/original/4X/8/7/a/87ab2f3173dbd5f3df0b5e4d36f52db791700a85.png)

Maybe one of you have an intelligent idea how to solve this problem?

In the Rhino file are some surfaces to test different angles of intersections.  
[BisectorPlaneDemo.3dm](https://discourse.mcneel.com/uploads/short-url/eS1r2O5YImZoWvR9axue87Xa71j.3dm) (3.6 MB)

Thanks a lot !

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**Author:** ![Willem](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/willem/32/554347_2.png) [@Willem](https://discourse.mcneel.com/u/Willem)\
**Post date:** [September 9, 2021, 10:46am UTC](https://discourse.mcneel.com/t/create-bisector-plane-of-two-intersecting-surfaces-solved/129907/2 "2021-09-09T10:46:35Z")

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Hi Leonard,

I did a quick rewrite of your script to give the reult you are after in this setup.  
Note the comments in the code for additions feedback.

[BisectorPlane\_wd.py](https://discourse.mcneel.com/uploads/short-url/rRQ207qfkTq3Lovs0e7WtpEl6tJ.py) (1.8 KB)

 ![image](https://global.discourse-cdn.com/mcneel/uploads/default/original/4X/7/9/6/79683ae31b10381002b63d82e44d10cfbf28c078.png)

Does this help?

\_willem

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**Author:** ![leonardruven](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/leonardruven/32/652016_2.png) [@leonardruven](https://discourse.mcneel.com/u/leonardruven)\
**Post date:** [September 10, 2021, 7:26pm UTC](https://discourse.mcneel.com/t/create-bisector-plane-of-two-intersecting-surfaces-solved/129907/3 "2021-09-10T19:26:02Z")

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Thank Willem for your help !

I tried with some examples and it works perfect.

Highly appreciate your quick fix !

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**Author:** ![PaleBlueDot](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/palebluedot/32/758849_2.png) [@PaleBlueDot](https://discourse.mcneel.com/u/PaleBlueDot)\
**Post date:** [January 2, 2026, 7:23pm UTC](https://discourse.mcneel.com/t/create-bisector-plane-of-two-intersecting-surfaces-solved/129907/4 "2026-01-02T19:23:17Z")

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[xyz.py](https://discourse.mcneel.com/uploads/short-url/3GJklOwk94lzsdz4qu94Fzde740.py) (4.2 KB)

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**Author:** ![Tom\_P](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/tom_p/32/766520_2.png) [@Tom\_P](https://discourse.mcneel.com/u/Tom_P)\
**Post date:** [January 2, 2026, 11:45pm UTC](https://discourse.mcneel.com/t/create-bisector-plane-of-two-intersecting-surfaces-solved/129907/5 "2026-01-02T23:45:05Z")

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as this old topic popped up again i added (solved) to the title

> [@leonardruven](#):
>
> Highly appreciate your quick fix !