I can see in the last TIP N° 14154 : How to add directional arrows to 3D polyline linetype and to spline?what I suppose to be 3D polylines with arcs but I'm not able to do this.Is it possible because I can  see nothing on the internet ?

3D Polylines cannot contain arc segments.  Help for the command is very explicit about that:
AutoCAD 2025 Help | 3DPOLY (Command) | AutodeskKent Cooper2024-06-25 13:38:27

Yes Kent I know that it's normally not possible but from what I see in the image of the TIP N£ 14154 ...Could it come from an other software or is there any other solution like a CADForum application.I would be very interested to get the way to do it for example for the 3D closed polyline that I use to navigate around 3 D solids when using the ANIPATH command.
philippe JOSEPH2024-06-25 17:11:01

You should be able to construct the 3D path in pieces, changing the UCS as appropriate to each portion, and if the ends of the pieces meet accurately, JOIN them together in a Spline.  Whether there's anything out there to automate any of the steps, I don't know.

You cannot fillet 3D polylines using internal AutoCAD tools but you can do that e.g. with the 3Dfillet utility - see Download.

Hello Vladimir and Kent, I have tested various 2D polylines with arcs to be joined with PEDIT and it doesn't work. I will try the 3Dfillet utility if I find it.I have found it, tested it and it works on the 3D polyline that I use in the ANIPATH command.I hope that it will improve the fluidity of my videos.
philippe JOSEPH2024-06-26 10:32:51

[QUOTE=philippe JOSEPH].... I have tested various 2D polylines with arcs to be joined with PEDIT and it doesn't work. ....[/QUOTE]If they are not co-planar, join them together with the JOIN command, not with PEDIT.  The result will be a Spline.  I imagine the 3D fillet utility you refer to is just an automating of the same thing, changing the object type of 3D Polylines that you apply it to.

Hello Kent and Vladimir, at first I was happy that the 3Dfillet utility was working but it worked only one time for a "radius" and no more on the rest of the 3D polyline, then I realized when trying to place a radius dimension that it wasn't a radius but a lot of little lines.Then I did a test by exploding my 3D polyline and manually filleting R:4000 each and every corner and it worked fine even if 3D without having to set an UCS individually for each fillet.Then I did the command JOIN on the assembly of lines and arcs but it didn't work as : non coplanar I suppose.Eventually see may AutoCAD file : DISCOVER THE ANIPATH COMMAND to see what is the use of my 3D polyline.