topic Re: Why does joining arcs and polylines creates splines? in AutoCAD LT Forum

AutoCAD LT 2021 - Why does joining arcs and polylines creates splines?

Anonymous — Wed, 26 Oct 2022 08:52:04 GMT

I'm working in AutoCAD LT 2021. All the lines are on the same 2D plane, 0 Z coordinate, and were imported from the same Rhino dwg export.

Bizarrely if i draw a line/polyline and an arc in AC LT the join command creates a polyline. Its only with imported (as in the attached door outline) which join into splines. Is this an import/export setting? Is there a function to regulate this?

Thanks

[ The subject line of this post has been edited to include the product name by @handjonathan ]

Re: Why does joining arcs and polylines creates splines?

cadffm — Mon, 10 May 2021 11:54:17 GMT

Hi,

your arcs created in a another coordinate system (select an arc and see the last properties "Normal X,Y,Z" in your ^properties palette (CTRL+1) or use command: LIST

You will see the normal is not 1

in this case join creates splines.

Sorry, i don't know a simple way to change this in LT, except redrawing

Re: Why does joining arcs and polylines creates splines?

pendean — Mon, 10 May 2021 12:44:08 GMT

See one of hundreds of similar posts https://forums.autodesk.com/t5/autocad-forum/join-makes-splines-instead-of-polylines/td-p/6438577

If you have access to full AutoCAD you can try this https://forums.autodesk.com/t5/autocad-forum/joining-polylines-converts-to-spline/m-p/5986241#M109173

If not, in LT try something like this on your objects BEFORE you join them https://forums.autodesk.com/t5/autocad-lt-forum/joining-arcs-and-lines-creates-splines/m-p/6431934#M141041

HTH

Re: Why does joining arcs and polylines creates splines?

steven-g — Mon, 10 May 2021 15:04:46 GMT

Your arc's are upside down (the normals that @cadffm mentions) to fix it you need to change the ucs to 'front' then rotate the arcs 180° around the centre of the front line. Then change the ucs back to world. Then a polyline will be created with join.

Does Rhino perhaps use clockwise arcs?

Re: Why does joining arcs and polylines creates splines?

Anonymous — Mon, 17 May 2021 11:04:03 GMT

Thank you all for the info. I'm looking into how rhino exports them as this seems to been the source of the problem.

Re: Why does joining arcs and polylines creates splines?

Robert.SmythXB2PJ — Tue, 25 Oct 2022 22:05:30 GMT

If it is a 3D part that you are working with then isolate the part and go to the front face view, create a flat shot with hidden lines off.

explode the result and use the join command to create a 2D polyline.

Re: AutoCAD LT 2021 - Why does joining arcs and polylines creates splines?

simonquinn — Sun, 05 Apr 2026 18:52:22 GMT

i have the same problem! no idea when arcs on the same 2d plane turn to splines in the 3d space. i can literally copy and paste the same arcs and lines on a 2d space and join them with no problem