Leaderboard

@PGia Thanks for the encouragement and checking the results. I measure from the vertices instead of the lines. Those are calculated and the lines are just to connect the points. So perpendicular to the middle of segments of the centerline will always be a bit off, but if you measure from the vertices it should be centered correctly. Just like @GP_ said. I kept going in the same direction and I have made some improvements and got rid of some bugginess: The centerline should be a little more accurate now because of extra measurements (blue line) Crossing polylines get sharp corners on negative side Corner checks are done on all intersections of temporary line now (red line) More error checking so it doesn't crash on some of the example lines I left all of the 'animation' code commented out so you can give it a try ;| ; Calculate centerline between two polylines - dexus ; Function checks intersections of the offsets of two lines to create a middle/avarage line. ; https://www.cadtutor.net/forum/topic/98778-hybrid-parallel/page/6/#findComment-677246 ; Version 0.1 - Initial release 19-11-2025 ; Version 0.2 - Added corner support on negative side of crossing polylines 27-11-2025 ; Version 0.3 - Extra check using distance between vertex and closest point 28-11-2025 ; Version 0.4 - Added error handler 28-11-2025 |; (defun c:cl (/ corners ent1 ent2 loop maxlen offset offsetdistance pts s1 s2 ss start te0 te1 te2 LM:ProjectPointToLine LM:intersections _addPoints _avarageAngle _cornerOffset _doOffset _getAnglesAtParam _getLength _polyline _side _wait *error*) (defun *error* (st) (if (wcmatch (strcase st t) "*break,*cancel*,*exit*") (redraw) (progn (vl-bt) (princ (strcat "\nOops! Something went wrong: ") st) ) ) (if (not (vlax-erased-p te0)) (entdel te0)) (if (and te1 (not (vl-catch-all-error-p te1))) (mapcar 'vla-delete te1)) (if (and te2 (not (vl-catch-all-error-p te2))) (mapcar 'vla-delete te2)) (princ) ) ;| ; Draw Polyline - dexus ; Draw a polyline from a list of points, but filter out colinear points ; @Param lst list of points ; @Returns ename of polyline |; (defun _polyline (lst closed / prev pts) (while lst (cond ( (and (cdr lst) prev (or (equal (cdr lst) prev 1e-8) ; Remove duplicate points (null (inters prev (car lst) prev (cadr lst))) ; Remove collineair points ) ) ) ((setq pts (cons (cons 10 (setq prev (car lst))) pts))) ) (setq lst (cdr lst)) ) (entmakex (append (list (cons 0 "LWPOLYLINE") (cons 100 "AcDbEntity") (cons 100 "AcDbPolyline") (cons 90 (length pts)) (cons 8 (getvar 'clayer)) (cons 70 (if closed 1 0)) ) (reverse pts) ) ) ) (defun _side (pline pnt / cpt end target der) ; https://www.theswamp.org/index.php?topic=55685.msg610429#msg610429 (setq cpt (vlax-curve-getClosestPointTo pline pnt) end (vlax-curve-getEndParam pline) target (vlax-curve-getParamAtPoint pline cpt) der (if (and (equal target (fix target) 1e-8) (or (vlax-curve-isClosed pline) (and (not (equal (vlax-curve-getStartParam pline) target 1e-8)) (not (equal end target 1e-8))) ) ) (mapcar '- (polar cpt (angle '(0 0) (vlax-curve-getFirstDeriv pline (rem (+ target 1e-3) end))) 1.0) (polar cpt (angle (vlax-curve-getFirstDeriv pline (rem (+ (- target 1e-3) end) end)) '(0 0)) 1.0) ) (vlax-curve-getFirstDeriv pline target) ) ) (minusp (sin (- (angle cpt pnt) (angle '(0.0 0.0) der)))) ) ;; Intersections - Lee Mac ;; mod - [int] acextendoption enum of intersectwith method (defun LM:intersections ( ob1 ob2 mod / lst rtn ) (if (and (vlax-method-applicable-p ob1 'intersectwith) (vlax-method-applicable-p ob2 'intersectwith) (setq lst (vlax-invoke ob1 'intersectwith ob2 mod)) ) (repeat (/ (length lst) 3) (setq rtn (cons (list (car lst) (cadr lst) (caddr lst)) rtn) lst (cdddr lst)) ) ) (reverse rtn) ) (defun _getLength (ent) (- (vlax-curve-getDistAtParam ent (vlax-curve-getEndParam ent)) (vlax-curve-getDistAtParam ent (vlax-curve-getStartParam ent)) ) ) (defun _wait (msec) (not ( (lambda (start) (while (< (- (getvar 'millisecs) start) msec)) ) (getvar 'millisecs) ) ) ) (defun _addPoints (lst ent pts / len) (setq len (_getLength ent)) (setq lst (mapcar (function (lambda (pt) (list (/ (vlax-curve-getDistAtPoint ent pt) len) pt))) lst)) (setq pts (append lst pts)) ; Animation ; (setq pts (vl-sort pts (function (lambda (a b) (< (car a) (car b)))))) ; (redraw) ; ( ; (lambda (lst) ; (while (cadr lst) ; (grdraw (cadar lst) (cadadr lst) 3) ; (setq lst (cdr lst)) ; ) ; ) ; pts ; ) ; (vla-update ent) ; (_wait 40) ; End animation pts ) (defun _doOffset (offset / lst rtn) ; Global vars: pts ent1 ent2 s1 s2 te1 te2 (setq te1 nil) (setq te2 nil) (setq rtn (cond ((equal offset 0.0 1e-8) (if (setq lst (LM:intersections ent1 ent2 acExtendNone)) (setq pts (_addPoints lst ent1 pts)) ) lst ) ( (or ; Make offset (vl-catch-all-error-p (setq te1 (vl-catch-all-apply 'vlax-invoke (list ent1 'Offset (if s1 offset (- offset)))))) (vl-catch-all-error-p (setq te2 (vl-catch-all-apply 'vlax-invoke (list ent2 'Offset (if s2 offset (- offset)))))) ) (princ "\nOffset failed. ") nil ) ((setq lst (LM:intersections (car te1) (car te2) acExtendNone)) (setq pts (_addPoints lst (car te1) pts)) lst ) ) ) (if (and te1 (not (vl-catch-all-error-p te1))) (mapcar 'vla-delete te1)) (if (and te2 (not (vl-catch-all-error-p te2))) (mapcar 'vla-delete te2)) rtn ) ;| ; Project Point onto Line - Lee Mac ; @Param pt point to project ; @Param p1 first point of line ; @Param p2 second point of line ; @Returns projected point |; (defun LM:ProjectPointToLine ( pt p1 p2 / nm ) (setq nm (mapcar '- p2 p1) p1 (trans p1 0 nm) pt (trans pt 0 nm)) (trans (list (car p1) (cadr p1) (caddr pt)) nm 0) ) (defun _getAnglesAtParam (ent pa / ang1 ang2) (if (and (vlax-curve-isClosed ent) (= pa 0)) ; Special case for closed Polyline (setq ang1 (vlax-curve-getFirstDeriv ent 1e-14) ang2 (vlax-curve-getFirstDeriv ent (- (fix (vlax-curve-getEndParam ent)) 1e-14))) (setq ang1 (vlax-curve-getFirstDeriv ent (+ pa 1e-14)) ang2 (vlax-curve-getFirstDeriv ent (- pa 1e-14))) ) (if (and ang1 ang2) (list (angle '(0 0 0) ang1) (angle '(0 0 0) ang2) ) ) ) ;| ; Avarage Angle - dexus ; Get angle of a line between two angles ; @Param ang1 real - Angle in radians ; @Param ang2 real - Angle in radians ; @Returns real - Angle in radians |; (defun _avarageAngle (ang1 ang2) (if (< (rem (+ ang1 pi) (+ pi pi)) (rem (+ ang2 pi) (+ pi pi)) ) (+ (* (- ang2 ang1) 0.5) ang1) (+ (* (- ang1 ang2) 0.5) ang2) ) ) ;| ; Calculate exact offset distance on a corner - dexus ; pt1 - Point on corner ; pt2 - Point on other side ; pt3 - Center for bisector ; pt4 - Target for corner of the offset ; pt5 - Find perpendicular point for offset distance ; / ; / ; -------- pt1 pt5 ; \ / ; pt4 ; \ ; ---- pt3 ----- pt2 ----- ; ; @Param ent1 Line to check corners ; @Param ent2 Opposing line ; @Returns List of offset distances (pt1 -> pt5) to calculate |; (defun _cornerOffset (ent1 ent2 / ang1 ang2 ang3 index pt1 pt2 pt3 pt4 pt5 rtn) (setq index 0) (repeat (fix (vlax-curve-getEndParam ent1)) (and (setq pt1 (vlax-curve-getPointAtParam ent1 index)) ; Point on corner (setq ang1 (_getAnglesAtParam ent1 index)) ; Angles of pt1 (setq ang1a (_avarageAngle (car ang1) (cadr ang1))) (setq te0 (entmakex (list (cons 0 "line") (cons 10 pt1) (cons 11 (polar pt1 (- ang1a halfPi) 1))))) ; Temp line for finding the angle on the other side (foreach pt2 (LM:intersections (vlax-ename->vla-object te0) ent2 acExtendThisEntity) ; Point on other side (and (setq ang2 (_getAnglesAtParam ent2 (vlax-curve-getParamAtPoint ent2 pt2))) ; Angle of pt2 (if (equal (rem (car ang1) pi) (rem (car ang2) pi) 1e-8) ; Is parallel? (and (setq pt3 (mapcar (function (lambda (a b) (* (+ a b) 0.5))) pt1 pt2)) ; Midpoint (setq ang3 (car ang1)) ; Same angle als ang1 ) (and (setq pt3 (inters pt1 (polar pt1 (car ang1) 1) pt2 (polar pt2 (car ang2) 1) nil)) ; Find center for bisector (setq ang3 (_avarageAngle (angle pt1 pt3) (angle pt2 pt3))) ; Angle of bisector ) ) (setq pt4 (inters pt3 (polar pt3 ang3 1) pt1 (polar pt1 (+ ang1a halfPi) 1) nil)) ; Find target for corner of the offset (setq pt5 (LM:ProjectPointToLine pt4 pt1 (polar pt1 (+ (car ang1) halfPi) maxlen))) ; Find perpendicular point for offset distance (setq rtn (cons (distance pt1 pt5) rtn)) ; Return offset distance ; Animation ; (progn ; (redraw) ; (grdraw pt1 pt2 1) ; (grdraw pt4 pt5 2) ; (grdraw pt1 pt5 2) ; (vla-update ent1) ; (_wait 120) ; ) ; End Animation ) ) ) (if (not (vlax-erased-p te0)) (entdel te0)) (setq index (1+ index)) ) rtn ) (if (and (not (while (cond ((not (setq ss (ssget '((0 . "LWPOLYLINE"))))) (princ "\nNothing selected. Try again...\n") ) ((/= (sslength ss) 2) (princ "\nSelect 2 polylines! Try again...\n") ) ((and (setq ent1 (ssname ss 0)) (setq ent2 (ssname ss 1)) (setq ent1 (vlax-ename->vla-object ent1)) (setq ent2 (vlax-ename->vla-object ent2)) ) nil ; Stop loop ) ) ) ) ent1 ent2 ) (progn (setq s1 (_side ent1 (if (< ; Check closest point for edgecase with crossing lines in oposite directions (distance (vlax-curve-getStartPoint ent1) (vlax-curve-getEndPoint ent2)) (distance (vlax-curve-getEndPoint ent1) (vlax-curve-getEndPoint ent2)) ) (vlax-curve-getEndPoint ent2) (vlax-curve-getStartPoint ent2) ) ) ) (setq s2 (_side ent2 (vlax-curve-getStartPoint ent1) ) ) (if (not (numberp halfPi)) (setq halfPi (* pi 0.5))) (setq maxlen (* 1.1 (max (_getLength ent1) (_getLength ent2) ( (lambda (ent1 ent2 / step de1 div p_step dis dmax) (setq step (/ (setq de1 (vlax-curve-getDistAtParam ent1 (vlax-curve-getEndParam ent1))) 500) div step dmax 0.00) (while (< div de1) (setq p_step (vlax-curve-getPointAtDist ent1 div) dis (distance p_step (vlax-curve-getClosestPointTo ent2 p_step))) (if (> dis dmax) (setq dmax dis)) (setq div (+ div step)) ) dmax ) ent1 ent2 ) ) ) ) (mapcar ; Add half distances from closest point to every vertex (function (lambda (ent1 ent2 / index pt) (setq index 0) (repeat (fix (vlax-curve-getEndParam ent1)) (setq pt (vlax-curve-getPointAtParam ent1 index) corners (cons (* (distance pt (vlax-curve-getClosestPointTo ent2 pt)) 0.5) corners) index (1+ index)) ; Animation ; (redraw) ; (grdraw pt (vlax-curve-getClosestPointTo ent2 pt) 4) ; ( ; (lambda (mid) (grdraw mid (polar mid (+ (angle pt (vlax-curve-getClosestPointTo ent2 pt)) halfPi) (car corners)) 2)) ; (mapcar (function (lambda (a b) (* (+ a b) 0.5))) pt (vlax-curve-getClosestPointTo ent2 pt)) ; ) ; (vla-update ent1) ; (_wait 120) ; End animation ) )) (list ent1 ent2) (list ent2 ent1) ) (setq corners (vl-sort (append corners (_cornerOffset ent1 ent2) (_cornerOffset ent2 ent1)) '<) offsetdistance (/ maxlen 1024.0)) (if (LM:intersections ent1 ent2 acExtendNone) ; For crossing polylines, add negative values (setq offset (- maxlen) corners (append (mapcar '- (reverse corners)) corners)) (setq offset 0.0) ) (while (progn (while (and corners (> offset (car corners))) ; Calculated offset values to check (_doOffset (car corners)) (setq corners (cdr corners)) ) (setq loop ; Incremental check (cond ((> offset maxlen) nil) ((_doOffset offset) (setq start t)) ((not start) t) (start nil) ) ) (setq offset (+ offset offsetdistance)) loop ) ) (if pts ; Draw polyline (_polyline (mapcar 'cadr (vl-sort pts (function (lambda (a b) (< (car a) (car b)))))) (and (vlax-curve-isClosed ent1) (vlax-curve-isClosed ent2)) ) ) ) ) (redraw) (princ) ) And here is an animation of it working just because they are fun to look at :

The concept is incorrect. To be equidistant, every point on the centerline must be the same distance (perpendicular) from the two margins.