polyline centre point

[Johntosh]

I'm familiar with vlax get start and get end point but what about the midpoint?

[Lee Mac]

This will retrieve the midpt:

 

(defun c:mpt (/ l1 stpt enpt midpt)
   (setq l1 (car (entsel "\nSelect Line: ")))
   (setq stpt (cdr (assoc 10 (entget l1))))
   (setq enpt (cdr (assoc 11 (entget l1))))
   (setq midpt
       (polar
           stpt
           (angle stpt enpt)
           (/ (distance stpt enpt) 2)
       ) ; end polar
   ) ; end setq
   (princ)
) ; end mpt

But doesn't use Active X methods, (I'm not too familiar with them)

[Johntosh]

Thanks Lee

 

Am I right in thinking this is only for a line and not a polyline?

[Lee Mac]

Sorry John,

Slight error in my first code - corrected

 

But yes, sorry, it is for lines only.

[Johntosh]

Thanks all the same

 

I'd like to use polar and angle as I learn more...and know I know how.

 

[lpseifert]

try this

(defun c:test (/ oldosnap crv crv-obj endpt totlen middist midpt)
(vl-load-com)
(setq oldosnap (getvar "osmode"))
(setvar "osmode" 0)
(command "ucs" "w")
(if (/= (getvar "pdmode") 3)(setvar "pdmode" 3))
(setq crv (entsel "Select curve: ")
     crv-obj (vlax-ename->vla-object (car crv))
     endpt (vlax-curve-getEndPoint crv-obj)
     totlen (vlax-curve-getDistAtPoint crv-obj endpt) 
     middist (/ totlen 2.0)
     midpt (vlax-curve-getPointAtDist crv-obj middist)
     )
(command "Point" midpt)
(command "ucs" "p")
(setvar "osmode" oldosnap)
(princ (strcat "\nA point was placed at the midpoint of the curve at " (rtos (car midpt) 2 2)"," (rtos (cadr midpt) 2 2))) 
(princ)
)

[Johntosh]

Thanks Ipseifert.

 

I'm not sure but is this for a polyline with just two points?

 

I think I can work out how to get to the 2 inner-most points however and work from there.

[devitg]

Thanks Ipseifert.

 

I'm not sure but is this for a polyline with just two points?

 

I think I can work out how to get to the 2 inner-most points however and work from there.

 

As I make a test , it work for any 2d enty , and even to a 3d poly .

 

LINE

ARC

CIRCLE

OPEN POLY

CLOSED POLY

SPLINE

3DPOLY

all enty mid point.dwg

[lpseifert]

Thanks Ipseifert.

 

I'm not sure but is this for a polyline with just two points?

 

I think I can work out how to get to the 2 inner-most points however and work from there.

It finds the length of the curve (vlax-curve which includes lines, polylines and a bunch of other entities) divides it by 2 and puts a point there. Did you try it?

[Johntosh]

Ah! Sorry, I only read it and believing that a curve only existed between two points.

 

I hadn't known fully about curves.