AutoCAD - 2D polylines > 3D polylines

2D polylines > 3D polylines

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Printed Date: 11.Jun.2026 at 15:54

Topic: 2D polylines > 3D polylines

Posted By: AlistairB
Subject: 2D polylines > 3D polylines
Date Posted: 15.Mar.2010 at 20:18

I have been given a bunch of underground tunnel outlines as 2D polylines and a recent survey that lists 3D survey points at regular intervals down these tunnels. I need to recreate 3D tunnel outlines from the 2D outlines and the 3D survey points.

Can anyone suggest an efficient way to achieve this goal.

thanks
Alistair

Replies:

Posted By: Vladimir Michl
Date Posted: 15.Mar.2010 at 21:13

You can use the 2D3DPOLY Lisp tool available on the Download page to convert 2D polylines to 3D polylines (change the object type). But if mean using the profiles to create a 3D solid from the sequential profiles, use the [CMD]LOFT[/CMD] command.

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Vladimir Michl (moderator)
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Posted By: AlistairB
Date Posted: 15.Mar.2010 at 22:09

Thanks Vladimir. 2D>3D lisp routine works great. thanks. It's a good first step. Basically I have 2D linework that represents 3D tunnel outlines. These lines show the walls of the tunnels in great detail, digitized from old paper maps. All the lines are at 0m elevation. I want to maintain the detail of the tunnel walls in x and y, but add a z value to each point derived from the new 3D survey of the tunnel floor so that the tunnels are in correct 3D space. Any further suggestions would be much appreciated.

Posted By: CarlB
Date Posted: 15.Mar.2010 at 22:11

***edit - I posted this before I saw your last entry**

Depends what kind of 3d tunnel outline-

3dpolylines at each of 4 corners or some interval,

3dmesh of tunnel walls

3dsolid, tunnel could be the solid or a tunnel through a solid

If tunnel has a constant cross-section, could define a single 3dpolyline along some path and use this for the LOFT command, as a variation of Vladimir's suggestion.

**UPDATE**

A thought, maybe you can do some manipulatipons in Excel to create points for a 3d polyline.

say put polyline x-y data (vertices) in excel. In a separate column keep running length.

In a separate table have surveyors data, running length versus elevation. Then in a column alongside the x-y data, do a Vlookup of survey table based on running length to get an elevation. Finally a column that concatenantes x,y, & z. With this You can use this column of data to paste in AutoCAD when running the "3dpolyline" command to draw the 3dpoly.

**Edit #2**

And if that is just not feasible, i'd suggest creating (having someone create) a lisp routine. user would select a 2d polyline & the survey points; routine would create a 3dplyline. for each 2dpoly vertex the routine would use the neares survey point to determine the z value for the 3dpoly.

you can email me with a drawing file that includes a typical 2dpoly & a few survey points.

c a b AT e e i t e a m DOT c o m

Posted By: AlistairB
Date Posted: 16.Mar.2010 at 01:40

Thanks Carl. I had considered generating the 3D points in excel, but it seemed a lot of work and I was hoping for a push button solution (ha). I did try a solution by connecting the survey points with a 3D poly, dividing this 3D poly using a simple line as a block, oriented perpendicular poly, then redigitizing the tunnel outline by snapping to the apparent intersection of these closely spaced blocks with the existing 2D polyline. It too is a lot of work and results in a degradation of the original x,y data. I'll try out the excel method as well to see if that turns out faster or better.

cheers

Alistair