Create 3D polyline parallel to another.

[bjohncarmichael]

Good afternoon all,  I have a road layout drawing made up of 3D polylines created from surveyed points.

Is it possible to create a parallel 3D polyline offset by a set amount in X-Y and by a different amount in Z value ?.

Or am I asking for too much !!!

Many thanks in advance, John.

[Pointdump]

Hi John,
You can offset and then MOVE 0,0,x.xx.
In Civil 3D you can use Stepped Offset.
Dave

[bjohncarmichael]

Thanks Dave but offset doesn't seem to work in 3D and I forgot to mention that the 3D polylines I want to create parallel are not straight !.

Unfortunately Civil 3D is above my pay scale !!.

[Pointdump]

John,
What was I thinking? Sorry, of course you're right, offset doesn't work with 3D.
From the end point of your 3D Poly, create a point, offset horizontally and vertically, then copy the 3D Poly snapping end to node. The FROM Command might come in handy.
Dave

[bjohncarmichael]

Thanks Dave, that will work on the straight lines but on curves it needs something more like an 3D version of offset !!

[Pointdump]

John,
OK, I see. Concentric 3D arcs would be needed. That would be tough.
So is this a roadway centerline that you're wanting to offset to create edges of travelway? Can you post your drawing?
Dave

[bjohncarmichael]

Hi Dave,

Thanks for your time on this. Unfortunately I cannot post the drawing as it belongs to my client and I believe there may be some copyright issues.

What I am trying to achieve is : we survey the line where the kerb (I believe its called a Curb on your side of the pond ?) meets the highway surface. What I want to do is create a 3D polyline of the top and back of kerb (curb!). So Z+110mm and offset to left of line by 150mm. I have several miles of these to create and I don't think its do-able without a lot of work.

[O_Eckmann · Accepted solution]

Hi,

You could try with this LISP  (fast written from functions found on web)

Process:

- extract 3D vertex

- convert to 2D vertex

- draw 2D polyline

- offset 2D polyline

- extract 2D vertex

- check same number of 2D vertex after offset as number of vertex of original 3D poly

- update 2D vertex to 3D vertex with X & Y from 2D and Z from 3D + vertical offset

- make 3D poly from 3D vertex

No test for offset value, or result of offset. Should work in most case but not every.

Olivier

[bjohncarmichael]

Thank you very much Oliver, that works brilliantly, you are a genius !.

Thanks again.  John.

[bjohncarmichael]

Can I just add, that in my line of work the Lisp you provided me with is one of the most useful time saving tools I have come across (I am easy to please !).

Thank you once again.