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Modeling
About Archicad's design tools, element connections, modeling concepts, etc.

CIRCLE TANGENT TO THREE LINES??? CANYOU DO IT?

Not applicable
Can anybody tell me how to draw a circle tangent to three lines or other circles?
I didn't know where to post this question - to Tips and tricks or to Wishes. Or to Wishes never to be...
Every time I need to do it I switch to AutoCAD and copy it back to AC.
So, you can do it in AutoCAD guys...
23 REPLIES 23
Not applicable
Almost a decade since this thread was started, and still no Archicad update to extend the options for the circle construction tool.
Here's a video of the technique I just came up with for constructing a circle tangent to three lines. I think it's faster than some of the earlier approaches mentioned.
http://www.youtube.com/watch?v=12TegajqE4E
I hope it helps any future searchers
Barry Kelly
Moderator
I would have just bisected the 2 angles between the 3 lines and the intersection of those bisecting lines is the centre for the circle you need.
Barry.
undefined
One of the forum moderators.
Versions 6.5 to 27
i7-10700 @ 2.9Ghz, 32GB ram, GeForce RTX 2060 (6GB), Windows 10
Lenovo Thinkpad - i7-1270P 2.20 GHz, 32GB RAM, Nvidia T550, Windows 11
Not applicable
Awesome. Happy to use that, thanks Barry.
Wish you'd weighed in with that sometime in the last nine years, before I made a video
Wonder if I should delete it again? Oh well.
Barry Kelly
Moderator
That was the gist of Laszlo's second post except the 3 lines there formed a triangle.
It even works for his example with the parallel lines.

I liked the video.
It is interesting to see other solutions too.
Barry.
One of the forum moderators.
Versions 6.5 to 27
i7-10700 @ 2.9Ghz, 32GB ram, GeForce RTX 2060 (6GB), Windows 10
Lenovo Thinkpad - i7-1270P 2.20 GHz, 32GB RAM, Nvidia T550, Windows 11
Hmooslechner
Moderator
https://www.dropbox.com/s/yvjz025ril226q1/3Circles1InnerCircleConsstruction.jpg

This should show the only way i found.. its german and my english is too poor to translate it .., but it could show You the way..

Maybe a real mathematic-GDL-Guru could develop such a thiing...
AC5.5-AC27EduAut, PC-Win10, MacbookAirM1, MacbookM1Max, Win-I7+Nvidia
Hmooslechner
Moderator
three circles with drifferent radius - 1 inner circle touches each..

This schould be a little work for a real GDL-guru - not me..


Did someone work on this problem?

here the not really simple geometric methode...

https://www.dropbox.com/s/yvjz025ril226q1/3Circles1InnerCircleConsstruction.jpg

There are som other mathematical methodes from Gauss and Descartes which are higher than my mathematic level - so if someone dit it bevore, i easyly could program a graphical user interface...
AC5.5-AC27EduAut, PC-Win10, MacbookAirM1, MacbookM1Max, Win-I7+Nvidia
Ben Cohen
Advocate
Or simply choose the correct construction method and click on the three lines !!
undefined
Ben Cohen
Mac and PC
Archicad (Latest Version) aus
www.4DLibrary.com.au
Barry Kelly
Moderator
Show-off!

Funny I always assumed that was tangential to 2 lines then pick a third point.
Just goes to show reading the prompt can help - clearly says pick a third point or tangential line.

Mind you I don't think I have ever needed to use this - that is my excuse.

Barry.
One of the forum moderators.
Versions 6.5 to 27
i7-10700 @ 2.9Ghz, 32GB ram, GeForce RTX 2060 (6GB), Windows 10
Lenovo Thinkpad - i7-1270P 2.20 GHz, 32GB RAM, Nvidia T550, Windows 11
Not applicable
Oy vey. I'll get back in my box then.
Ben Cohen
Advocate
hahaha
can't say I have ever need it either.....
Ben Cohen
Mac and PC
Archicad (Latest Version) aus
www.4DLibrary.com.au