Originally Posted by

**Lee Mac**
Thank you, Lee Mac. I was using your AddLWPolylineVertexV1-0.lsp routine. Could you possibly explain your code just a bit, I've got trouble understanding it.

I started breaking down the program line by line

Code:

;;----------------=={ Add LWPolyline Vertex }==---------------;;
;; ;;
;; Adds a new vertex to an LWPolyline at a point specified ;;
;; by the user; compatible with LWPolylines at any ;;
;; orientation, with varying width and arc segments. ;;
;;------------------------------------------------------------;;
;; Author: Lee Mac, Copyright © 2012 - www.lee-mac.com ;;
;;------------------------------------------------------------;;
;; Version 1.0 - 17-12-2012 ;;
;; ;;
;; First release. ;;
;;------------------------------------------------------------;;
(defun c:apv ( / a b e h l n p r w x z )
(while ;;inf loop
(progn (setq p (getpoint "\nPick Point for New Vertex: "))
(cond
( (null p) nil) ;; 1st cond - if p not equal 0 return nil
( (null (setq e (nentselp p))) ;; 2nd cond ? The nentselp function returns a 4×4 transformation matrix. What for?
(princ "\nPoint does not lie on an LWPolyline.") ;; so if the returned matrix is empty (nil), print this
)
( (= 4 (length e)) ;; 3rd cond - ??
(princ "\nObject is Nested.") ;; what is nested object?
)
( (/= "LWPOLYLINE" (cdr (assoc 0 (entget (setq e (car e)))))) ;; 4th cond - compare. If not equal...
(princ "\nObject is not an LWPolyline.") ;; ...print this
)
)
)
)
(if (and p e ;; expression returns T if both p and e are not nil, else nil
(setq p (vlax-curve-getclosestpointto e (trans p 1 0)) ;; the UCS is rotated 90 degrees counterclockwise around the WCS Z axis?? Closest point between e and rotated list
n (vlax-curve-getparamatpoint e p) ;; still don't understand what getparamatpoint means
)
)
(if (not (equal n (fix n) 1e-8)) ;; checks if not equal - n and its truncated value with fuzz distance of 1e-8
(progn
(setq e (entget e)
h (reverse (member (assoc 39 e) (reverse e))) ;; returns list consisting of 14 lists - what for?
l (LM:LWVertices e)
z (assoc 210 e)
)
(repeat (fix n)
(setq a (cons (car l) a)
l (cdr l)
)
)
(setq x (car l)
r (- n (fix n))
w (cdr (assoc 40 x))
w (+ w (* r (- (cdr (assoc 41 x)) w)))
b (atan (cdr (assoc 42 x)))
)
(entmod
(append h
(apply 'append (reverse a))
(list
(assoc 10 x)
(assoc 40 x)
(cons 41 w)
(cons 42 (tan (* r b)))
)
(list
(cons 10 (trans p 0 (cdr z)))
(cons 40 w)
(assoc 41 x)
(cons 42 (tan (* (- 1.0 r) b)))
)
(apply 'append (cdr l))
(list z)
)
)
)
)
)
(princ)
)
;; Tangent - Lee Mac
;; Args: x - real
(defun tan ( x )
(if (not (equal 0.0 (cos x) 1e-10))
(/ (sin x) (cos x))
)
)
;; LW Vertices - Lee Mac
;; Returns a list of lists in which each sublist describes
;; the position, starting width, ending width and bulge of the
;; vertex of a supplied LWPolyline
(defun LM:LWVertices ( e )
(if (setq e (member (assoc 10 e) e))
(cons
(list
(assoc 10 e)
(assoc 40 e)
(assoc 41 e)
(assoc 42 e)
)
(LM:LWVertices (cdr e))
)
)
)
(vl-load-com) (princ)
;;------------------------------------------------------------;;
;; End of File ;;
;;------------------------------------------------------------;;

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