# Move circle along line until it touches another circle

**URL:** <https://discourse.mcneel.com/t/move-circle-along-line-until-it-touches-another-circle/206674>\
**Category:** Rhino\
**Tags:** mac, geometry, circle\
**Created:** [July 2, 2025, 2:09pm UTC](https://discourse.mcneel.com/t/move-circle-along-line-until-it-touches-another-circle/206674 "2025-07-02T14:09:49Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![Davi\_Sales\_Barreira](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/davi_sales_barreira/32/606929_2.png) [@Davi\_Sales\_Barreira](https://discourse.mcneel.com/u/Davi_Sales_Barreira)\
**Post date:** [July 2, 2025, 2:09pm UTC](https://discourse.mcneel.com/t/move-circle-along-line-until-it-touches-another-circle/206674/1 "2025-07-02T14:09:49Z")

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I have two circles, and I want to move one of them along a certain direction until it hits the other one. Any ideas on how this could be done? Here is a picture of what I’m looking for. The circle on the top left has have its center moving along the red diagonal line.

 ![image](https://global.discourse-cdn.com/mcneel/uploads/default/original/4X/0/e/4/0e4459172caf4a69b467e7c650f9852e65d2dc90.png)

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**Author:** ![martinsiegrist](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/martinsiegrist/32/498369_2.png) [@martinsiegrist](https://discourse.mcneel.com/u/martinsiegrist)\
**Post date:** [July 2, 2025, 2:32pm UTC](https://discourse.mcneel.com/t/move-circle-along-line-until-it-touches-another-circle/206674/2 "2025-07-02T14:32:06Z")

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You can move the large circle to any point on the small circle and then draw a line from the small circle center to the large circle center. Extend the line so it ends on the large circle. Then rotate around the center of the small circle until the end of the red line lies on one of the X lines. There’s your center point.

 ![image](https://global.discourse-cdn.com/mcneel/uploads/default/original/4X/9/5/1/951e8c674219aefe444b839b030497084d105405.png)

 ![image](https://global.discourse-cdn.com/mcneel/uploads/default/original/4X/9/1/3/91398b113335a47b6140075f7cf5081b31557750.png)

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**Author:** ![martinsiegrist](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/martinsiegrist/32/498369_2.png) [@martinsiegrist](https://discourse.mcneel.com/u/martinsiegrist)\
**Post date:** [July 2, 2025, 4:06pm UTC](https://discourse.mcneel.com/t/move-circle-along-line-until-it-touches-another-circle/206674/3 "2025-07-02T16:06:59Z")

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Maybe someone at McNeel could explain how to add constraints to this sketch.

 ![image](https://global.discourse-cdn.com/mcneel/uploads/default/original/4X/f/a/3/fa3c7797f8864f23a2a0265d7920f552a768096c.png)

I have done enough Solidworks stuff to know how constraints should work but I’m sort of stuck already with a tangent arc or circle tangent to line.

[constraint-struggle.3dm](https://discourse.mcneel.com/uploads/short-url/lXg8dShQddGlUN3CJAf7dSaATrG.3dm) (78.0 KB)

PS: For those who have never seen constraints in Rhino, it’s a feature in Rhino 9 WIP

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<div class="post-metadata">

**Author:** ![martinsiegrist](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/martinsiegrist/32/498369_2.png) [@martinsiegrist](https://discourse.mcneel.com/u/martinsiegrist)\
**Post date:** [July 2, 2025, 4:10pm UTC](https://discourse.mcneel.com/t/move-circle-along-line-until-it-touches-another-circle/206674/4 "2025-07-02T16:10:25Z")

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Managed to set up some of it

 ![image](https://global.discourse-cdn.com/mcneel/uploads/default/original/4X/c/3/5/c35a1c43e41357c0e297ebc253ac278acdb4e3c0.png)