Topic: Correct Self Intersecting Polylines

[mailmaverick]

How to correct Self-Intersecting Polylines to not Self-Intersecting Polylines ?
I'm referring to LWPolyline (in two dimensions only).

[ribarm]

Interesting task, but I don't want to share the code...

[renkor]

Hello,

wow it`s a good task. where can we find some lisp like yours?

Best regards.

[ribarm]

Hello,

wow it`s a good task. where can we find some lisp like yours?

Best regards.

I don't know, I know that I wrote my version and it's in my library which will be available after I die...

[mailmaverick]

Hi,

Can someone please share the Code to automatically correct Self-Intersecting 2-D LWPolylines please.
Thanks a lot.

[Rod]

If you are using AutoCAD Civil or Map you can utilise the Mapclean command through lisp.
I would use the "break crossing objects" first then "dissolve psuedo nodes" on the results (that are not closed)
Sorry don't have any code for you.

[danAllen]

I usually only need this for drawing hatches in a closed boundary. I find it easiest to explode the offending pline, and use BPOLY to draw a new one. Also OVERKILL often will fix the extra vertices. Try also CAB's break all.
http://www.theswamp.org/index.php?topic=10370.msg132035#msg132035

[nekonihonjin]

Hi,

Can someone please share the Code to automatically correct Self-Intersecting 2-D LWPolylines please.
Thanks a lot.

if it's a closed pline, just hatch the inside with "pick points", the right-click in the hatch and "generate boundary"
the just erase both the hatch and the old selfintersecting line.

[dexus]

I came across this problem as well and couldn't find anyone who posted code to fix the polylines.
So I made a version myself using boundaries. It's not the quickest, but does the job (including some known flaws).

Code - Auto/Visual Lisp: [Select]

1. (defun c:fixSelfIntersecting (/ sel box app lst dis n ss x y enl rtn cmdecho nomutt clayer *error*)
2.   ; --------------------------------------------------------- ;
3.   ;  Fix Self Intersecting polylines - dexus                  ;
4.   ; --------------------------------------------------------- ;
5.   ;  Tries to split self intersecting polylines into          ;
6.   ;  seperate closed polylines.                               ;
7.   ;                                                           ;
8.   ;  Known flaws:                                             ;
9.   ;  - Doesnt work on open polylines, only closed             ;
10.   ;  - Resets width of all polyline segment to 0              ;
11.   ;  - Some very, very small regions may be skipped           ;
12.   ;  - Repeatedly prints error of valid boundary not found.   ;
13.   ; --------------------------------------------------------- ;
14.  
15.   (defun *error* (st)
16.     (if (wcmatch (strcase st t) "*break,*cancel*,*exit*")
17.       (redraw)
18.       (princ "\nError! Something went wrong.")
19.     )
20.     (if cmdecho (setvar 'cmdecho cmdecho))
21.     (if nomutt (setvar 'nomutt nomutt))
22.     (if clayer (setvar 'clayer clayer))
23.     (setvar 'modemacro "")
24.     (princ)
25.   )
26.  
27.   (if (setq ss (ssget '((0 . "LWPOLYLINE") (-4 . "&=") (70 . 1))))
28.   )))
29.     (repeat (setq n (sslength ss))
30.       (if
31.         (and
32.           (setq e (ssname ss (setq n (1- n))))
33.           (setq sel (ssadd e))
34.           (setq box (LM:ssboundingbox sel))
35.         )
36.         (progn
37.           (setq app (vlax-get-acad-object)
38.                 dis (/ (apply 'distance box) 20.0)
39.                 lst (mapcar '(lambda (a o) (mapcar o a (list dis dis))) box '(- +))
40.                 dis (* dis 1.5)
41.                 cmdecho (getvar 'cmdecho)
42.                 nomutt (getvar 'nomutt)
43.                 clayer (getvar 'clayer))
44.  
45.           (apply 'vlax-invoke
46.             (vl-list* app 'zoomwindow
47.               (mapcar '(lambda (a o) (mapcar o a (list dis dis 0.0))) box '(- +))
48.             )
49.           )
50.           (setq enl (entlast)
51.                 rtn (ssadd))
52.           (while (setq tmp (entnext enl))
53.             (setq enl tmp)
54.           )
55.  
56.           (setq x (caar lst)
57.                 y (cadar lst)
58.                 dis (/ dis 4.0))
59.  
60.           (setvar 'cmdecho 0)
61.           (setvar 'nomutt 1)
62.           (setvar 'clayer (cdr (assoc 8 (entget e))))
63.           (command "_.-boundary" "_a" "_b" "_n" sel "" "_i" "_y" "_o" "_p" "")
64.           (while (<= x (caadr lst))
65.             (while (<= y (cadadr lst))
66.               (command "_non" (list x y))
67.               (setq y (+ y dis))
68.             )
69.             (setq x (+ x dis)
70.                   y (cadar lst))
71.           )
72.           (while (< 0 (getvar 'cmdactive)) (command ""))
73.           (while (setq enl (entnext enl)) (ssadd enl rtn))
74.           (entdel e)
75.           (vla-zoomprevious app)
76.           (setvar 'cmdecho cmdecho)
77.           (setvar 'nomutt nomutt)
78.           (setvar 'clayer clayer)
79.           rtn ; This retuns the resulting polylines as a selection set in case you want to use this function inside of another function.
80.         )
81.       )
82.     )
83.   )
84.   (princ)
85. )
86.  
87. ;;----------------------------------------------------------------------;;
88. ;; Selection Set Bounding Box  -  Lee Mac                               ;;
89. ;; Returns a list of the lower-left and upper-right WCS coordinates of a;;
90. ;; rectangular frame bounding all objects in a supplied selection set.  ;;
91. ;; s - [sel] Selection set for which to return bounding box             ;;
92. ;;----------------------------------------------------------------------;;
93. (defun LM:ssboundingbox (s / a b i m n o)
94.   (repeat (setq i (sslength s))
95.     (if
96.       (and
97.         (setq o (vlax-ename->vla-object (ssname s (setq i (1- i)))))
98.         (vlax-method-applicable-p o 'getboundingbox)
99.         (not (vl-catch-all-error-p (vl-catch-all-apply 'vla-getboundingbox (list o 'a 'b))))
100.       )
101.       (setq m (cons (vlax-safearray->list a) m)
102.             n (cons (vlax-safearray->list b) n))
103.     )
104.   )
105.   (if (and m n)
106.     (mapcar '(lambda (a b) (apply 'mapcar (cons a b))) '(min max) (list m n))
107.   )
108. )
109.  
110. (princ)