Thread: AutoLisp - Draw polyline between middle of inserted points

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AutoLisp - Draw polyline between middle of inserted points

Hello everyone,

I'm having problems modifying/ creatig a lisp that does:
- draw pline
- p1 = first point = mid of (p1.1,p1.2)
- p2 = second point = mid of (p2.1,p2.2)
- p3 = third pint = mid of (p3.1,p3.2)
- and so on

What I have at the moment is:

Code:
```(defun c:pl-mid    ()
(setq p1-1 (getpoint "\n Insert p1-1:"))
(setq p1-2 (getpoint "\n insert p1-2:"))
(setq p2-1 (getpoint "\n insert p2-1:"))
(setq p2-2 (getpoint "\n insert p2-2:"))
(setq    px1-1 (car p1-1)
px1-2 (car p1-2)
px2-1 (car p2-1)
px2-2 (car p2-2)
)
(setq p1x-mid (/ (+ px1-1 px1-2) 2))
(setq p1y-mid (/ (+ py1-1 py1-2) 2))
(setq p2x-mid (/ (+ px2-1 px2-2) 2))
(setq p2y-mid (/ (+ py2-1 py2-2) 2))
(command "pline"
(list p1x-mid p1y-mid 0.0)
(list p2x-mid p2y-mid 0.0)
""
)
)```
What I don't manage to figure out is how to implement a continuous imput of points from wich to compute the middle distance as the next point of the polyline.
Thanks in advance for any imput.

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Re: AutoLisp - Draw polyline between middle of inserted points

Originally Posted by robertdq885441
Hello everyone,

What I don't manage to figure out is how to implement a continuous imput of points from wich to compute the middle distance as the next point of the polyline.
Thanks in advance for any imput.
Middle of the last pline created? Not sure if this is your intent:

Code:
```(defun c:pl-mid	(/ _mid p1-1 p1-2 p2-1 p2-2 mp1 mp2)
(defun _mid (1p 2p)
(mapcar (function (lambda (a b) (* (+ a b) 0.5))) 1p 2p)
)
(if (setq p1-1 (getpoint "\n Insert p1-1:"))
(while (and
(setq p1-2 (getpoint p1-1 "\n insert p1-2:"))
(setq p2-1 (getpoint p1-2 "\n insert p2-1:"))
(setq p2-2 (getpoint p2-1 "\n insert p2-2:"))
)
(command "pline"
"_non"
(setq mp1 (_mid p1-1 p1-2))
"_non"
(setq mp2 (_mid p2-1 p2-2))
""
)
(setq p1-1 (_mid mp1 mp2))
)
)
(princ)
)```

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Re: AutoLisp - Draw polyline between middle of inserted points

Code:
```(defun c:pl-mid ( / p1 p2 mp mpl clf )
(setq p1 (getpoint "\nPick 1st reference point: "))
(while (and
(if (null p1)
(progn
(initget 128)
(setq p1 (getpoint "\nPick 1st reference point (enter to exit - \"C\" (close)): "))
)
t
)
(if (not (or (eq p1 "C") (eq p1 "c")))
(progn
(setq p2 (getpoint "\nPick 2nd reference point (enter to exit): "))
(if (and p1 p2) (setq mp (mapcar '/ (mapcar '+ p1 p2) '(2. 2. 2.))))
(if (and p1 p2) (setq mpl (cons mp mpl)))
(setq p1 nil)
(if p2 t nil)
)
(progn
(setq mpl (cons p1 mpl))
nil
)
)
(if (and (not (or (eq (car mpl) "C") (eq (car mpl) "c"))) (> (length mpl) 1)) (progn (grdraw (car mpl) (cadr mpl) 1 1) t) t)
)
)
(if (or (eq (car mpl) "C") (eq (car mpl) "c")) (setq mpl (cdr mpl) clf t))
(entmake (append '((0 . "LWPOLYLINE") (100 . "AcDbEntity") (100 . "AcDbPolyline"))
(list (cons 90 (length mpl)))
(if clf '((70 . 1)) '((70 . 0)))
(list (cons 38 (caddr (trans (car mpl) 1 (trans '(0.0 0.0 1.0) 1 0 t)))))
(mapcar '(lambda (x) (cons 10 (trans x 1 (trans '(0.0 0.0 1.0) 1 0 t)))) (reverse mpl))
(list (cons 210 (trans '(0.0 0.0 1.0) 1 0 t)))
)
)
(command "_.regen")
(princ)
)```

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Re: AutoLisp - Draw polyline between middle of inserted points

marko_ribar thank you, it's exactly what I was looking for. It seems so complicated for such a "simple thing" in my opinion
I tryied to modify the code pbejse posted into something like:
Code:
```(defun c:pl-mid ()
(defun _mid (p1 p2)
(mapcar (function (lambda (a b) (* (/ a b) 2))) 1p 2p)
(setq p1-1 (getpoint "\n insert p1-1:"))
(setq p1-2 (getpoint "\n insert p1-2:")))
(command "pline"
(setq mp (_mid p1-1 p1-2))
""
)
(princ)
)```
but with no luck. i know I need a "while" loop somewere but I can't figure it out. (you do learn something new everyday )

pbejse thanks to you i had to look into what mapcar and lambda mean and do.

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Re: AutoLisp - Draw polyline between middle of inserted points

Originally Posted by robertdq885441
but with no luck. i know I need a "while" loop somewere but I can't figure it out. (you do learn something new everyday )

pbejse thanks to you i had to look into what mapcar and lambda mean and do.
You are welcome, but i'm still not sure of your intent

This?

Code:
```(defun c:pl-mid	( / _mid p1-1 p1-2 mp)
(defun _mid (1p 2p)
(mapcar (function (lambda (a b) (* (+ a b) 0.5))) 1p 2p)
)
(if (and (setq p1-1 (getpoint "\n insert p1-1:"))
(setq p1-2 (getpoint p1-1 "\n insert p1-2:"))
(setq mp (_mid p1-1 p1-2))
)
(while
(and (setq p2-1 (getpoint mp "\n insert p2-1:"))
(setq p2-2 (getpoint p2-1 "\n insert p2-2:"))
)
(command "pline" "_non" mp "_non" (setq mp (_mid p2-1 p2-2)) "")
)
)
(princ)
)```
or

Code:
```(defun c:pl-mid2 ( / _mid p1-1 p1-2 mp)
(defun _mid (1p 2p)
(mapcar (function (lambda (a b) (* (+ a b) 0.5))) 1p 2p)
)
(if (and (setq p1-1 (getpoint "\n insert p1-1:"))
(setq p1-2 (getpoint p1-1 "\n insert p1-2:"))
(setq mp (_mid p1-1 p1-2))
)
(progn
(command "_Pline" mp)
(while (> (getvar "CMDACTIVE") 0)
(if (and (setq p2-1 (getpoint mp "\n insert p2-1:"))
(setq p2-2 (getpoint p2-1 "\n insert p2-2:"))
)
(command (setq mp (_mid p2-1 p2-2)))
(command "")
)
)
)
)
(princ)
)```
Makes me wonder why not just use _m2p osnap when selecting the two other points and do away with the lisp code?

Curios is all

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Re: AutoLisp - Draw polyline between middle of inserted points

So my problem is that I have some topographic surveys of some roads with points taken only for the edge of the road. I need to draw a polyline that will represent the center line of the road. Each vertex of this polyline will be situated at the mid distance between the edge of the road. I have attached an example.

The problem with the last 2 versions you posted is that I end with a lot of polylines instead of one

I tried to take you're code line by line hoping it will give me a starting point but with no luck. I didn't knew what "_non" does, I remember reading about it somewhere but I forgot were and I have so little time at the moment .

P.S. Next time I'l try to be more explicit and post when not under the effect of

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Re: AutoLisp - Draw polyline between middle of inserted points

Originally Posted by robertdq885441

The problem with the last 2 versions you posted is that I end with a lot of polylines instead of one
The second code will only generate one polyline (defun c:pl-mid2 ()

Anyhoo, can't open the file though stuck in 2009 and i'm using my netbook where DwgTrueView is not installed. can you save the file to a lower version so i can have a look now rather than later?

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Re: AutoLisp - Draw polyline between middle of inserted points

Sure, I saved it in 2004 format.

I didn't saw that the command for the second routine was pl-mid2. This one work's great thank you.

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Re: AutoLisp - Draw polyline between middle of inserted points

Originally Posted by robertdq885441
Sure, I saved it in 2004 format.

I didn't saw that the command for the second routine was pl-mid2. This one work's great thank you.
Glad you had it sorted robertdq885441, play around with the code to include setting the preferred layer at the start of the routine and setting it back after the program is done

HINT: (Setvar/Getvar)
Also try to include an *error* sub for completeness

Cheers <--- save me a mug next time you step out for more

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