topic Re: Generate a 3D solid pipe in AutoCAD Forum

Generate a 3D solid pipe

rsalastopografia — Thu, 26 Jun 2025 02:41:50 GMT

Hello everyone,

I am working on a civil project where I had to stake out and then survey the installation of buried 12-inch HDPE pipes in the field.

The 3DPolyline I have represents the top of the pipe (the crown).

What I want to do is generate a 3D solid (pipe) based on this 3DPolyline, where:
- The top of the solid aligns with the 3Dpolyline.
- The pipe diameter is a user input, for example: 0.315 meters.
- The solid is modeled downward from the crown to the bottom of the pipe.

I tried using AutoLISP routines with vla-AddCylinder, sweep, loft, and even extruding regions along a path. However, all of these assume that the path is the centerline of the pipe, which is not my case.

Questions:
- Has anyone faced a similar modeling situation (surveyed pipe from top line)?
- Is there a reliable way to create a solid 3D pipe based on a polyline that is not the centerline?
- Can this be done in AutoLISP? Or should I use .NET or another method?

Any suggestions or sample code would be greatly appreciated.

Thanks in advance for your time and insights.

Vista levantamiento

It is required to generate this solid model starting from the crown down.

Re: Generate a 3D solid pipe

j.palmeL29YX — Thu, 26 Jun 2025 08:11:08 GMT

@rsalastopografia wrote:

What I want to do is generate a 3D solid (pipe) based on this 3DPolyline, where:
- The top of the solid aligns with the 3Dpolyline.

Is this what you're looking for? (As example I changed the color of one f the 3DPolylines to red and used that for a sweeping).

Re: Generate a 3D solid pipe

autoid374ceb4990 — Thu, 26 Jun 2025 13:47:00 GMT

Looks like @rsalastopografia has the solution, but does your LISP routine work except for the elevation? If so why not just move the result vertically by the proper amount?

Re: Generate a 3D solid pipe

rsalastopografia — Thu, 26 Jun 2025 15:51:36 GMT

Jürgen Palme, That's exactly what I was looking for. How did you do it? Could you please explain how you managed to generate the pipe solid from the 3D poly down? Did you use AutoCAD tools, Lisp, or some other programming language?

Re: Generate a 3D solid pipe

j.palmeL29YX — Thu, 26 Jun 2025 15:35:55 GMT

@autoid374ceb4990 wrote:

... why not just move the result vertically by the proper amount?

IMO (if I understand the intention of the OP right) the top of a moved pipe no longer follows exactly the 3DPolyline.

Re: Generate a 3D solid pipe

rsalastopografia — Thu, 26 Jun 2025 15:53:37 GMT

Jürgen Palme Could you please tell me how you managed to generate the pipe from the 3D poly, using the upper part of the pipe as a reference? It's exactly what I was looking for. It's a bit complicated because it has vertical elbows, and in this case, moving the 3D poly to the center of the pipe doesn't work. Looking forward to your comment. Best regards.

Re: Generate a 3D solid pipe

rsalastopografia — Thu, 26 Jun 2025 16:52:38 GMT

That's exactly what I was looking for. How did you do it? Could you please explain how you managed to generate the pipe solid from the 3D poly down? Did you use AutoCAD tools, Lisp, or some other programming language?

Re: Generate a 3D solid pipe

j.palmeL29YX — Thu, 26 Jun 2025 17:22:15 GMT

Sorry for the delay, I was busy with other project.

Hope you can follow the steps in this video:

(view in My Videos)

Re: Generate a 3D solid pipe

imadHabash — Thu, 26 Jun 2025 17:26:26 GMT

Hi,

As much as i understand your need and depending on @j.palmeL29YX first suggestion... draw circles that represent your pipe then convert them to region. Use Subtract command to get the right shape for your pipe .Now by Extrude command ( Path ) you will get the final good result that you asked for. Click on below image to see what i mean.

Re: Generate a 3D solid pipe

rsalastopografia — Thu, 26 Jun 2025 17:48:43 GMT

Simply brilliant. I thought I'd used Lisp, but I see they're common AutoCAD commands. Thanks for sharing those AutoCAD tips.

Re: Generate a 3D solid pipe

rsalastopografia — Thu, 26 Jun 2025 17:52:01 GMT

Your method for generating pipes from 3D Poly is very interesting. Thank you for sharing these tips.

Re: Generate a 3D solid pipe

j.palmeL29YX — Fri, 27 Jun 2025 04:22:21 GMT

@imadHabash wrote:

... Now by Extrude command ( Path ) you will get the final good result that you asked for.

Extrude (Path) is a nice idea, but in this example it doesn't give us the expected (needed) result.

(view in My Videos)

Re: Generate a 3D solid pipe

Washingtonn — Fri, 27 Jun 2025 15:16:08 GMT

Be careful at vertical offsets/risers/drops - at those locations, a polyline is coincident to the center of the pipe.