Get starting point of a polyline

[Radu Iordache]

Hello, can someone help with a simple lisp to get the coordinates of the start point of a lwpolyline in the form Y,X (north,east) and store them in a variable? Thanks a lot!

[Tharwat]

You can use the vlax-curve-getstartpoint or the first DXF 10 if you entget the entity.

[BIGAL]

Following on from Tharwat suggestion.

 

(setq ent (entsel "\nPick a pline ")) ; pick pline
(setq entg (entget (car ent)))  ; get entity values
(setq pt (cdr (assoc 10 entg))) ; get 1st point

or 

(setq obj (vlax-ename->vla-object (car  (entsel "\nPick a pline ")))) ; pick pline
(setq start (vlax-curve-getstartPoint obj)) ; get 1st point

 

[Tharwat]

It is not necessarily / required  to convert an entity to vla-object when using it with any of vlax-curve* functions.

[ronjonp]

On 3/11/2023 at 7:13 AM, Tharwat said:

It is not necessarily / required  to convert an entity to vla-object when using it with any of vlax-curve* functions.

Converting to vla-object then using  curve functions is also quite a bit slower.

(setq e (car (entsel)))
(setq o (vlax-ename->vla-object e))
(benchmark '((vlax-curve-getStartPoint e)(vlax-curve-getStartPoint o)))
;;;<Entity name: 1e9f2363150> 
;;;#<VLA-OBJECT IAcadLWPolyline 000001e9df9c2dc8> Benchmarking ..................Elapsed milliseconds / relative speed for 32768 iteration(s):
;;;
;;;    (vlax-curve-getStartPoint E).....1781 / 1.71 <fastest>
;;;    (vlax-curve-getStartPoint O).....3047 / 1.00 <slowest>
;;;
;;;---- Benchmark Utility: In memory of Michael Puckett ----
;;; 
;;;; 3 forms loaded from #<editor "<Untitled-0> loading...">

 

[Steven P]

Depends on the function of course, if you are processing a lot of lines then program speed can be an issue, only a few lines and the slowest thing is the user and their mouse.

 

I'd go first off with what I know works, and then speed it up if necessary

[mhupp]

11 hours ago, ronjonp said:

Converting to vla-object then using  curve functions is also quite a bit slower.

 

Even tho the documentation says vlax-curve-getstartPoint works with vla-objects  you can feed it entity names as well. i think this works with all vlax-curve functions.

 

-edit

Tharwat-ed

 

(setq SPT (vlax-curve-getstartPoint (car  (entsel "\nPick a pline ")))) ; get 1st point
(vl-cmdf "_.Circle" "_non" SPT "0.25")

 

Edited March 16, 2023 by mhupp