midpoint between two points?

[russell84]

hey guys if i have 2 pts stored in lisp

$P1 and $P2

how do i get the midpoint of those pts??

 

i have the below lisp that i'm trying to edit write to suite us..was originally written by a guy here but i want to show the details between the 2 points.

 

I want to show a line between the two points and on that line i want to show the slope, distance and direction by use of a arrow.

 

Would someone please be able to help me with the info part. I have got the line and cross to work so far.

 

You will see what i mean.

 

Thank you

 

(defun C:EXTRA ()
(setq oldlay (getvar "clayer"))

; #################  Gather Info  #################
;
(initget 1)
(setq $P1 (getpoint      "\nSTARTING POINT:  "))
(initget 1)
(setq $L1 (getreal       " - - LEVEL: "       ))
(setq $P1 (reverse (cdr (reverse $P1)))) ; remove Z coordinate
(if $GR
  (progn
     (setq $OGR $GR $GR nil)
     (setq $GR (getreal (strcat "\nGradient % <" (rtos $OGR 2) ">: " )))
     (if (= $GR nil)(setq $GR $OGR))
  );progn
  (progn
     (setq $GR nil)
     (setq $GR (getreal       "\nGradient % <1>: " ))
     (if (= $GR nil)(setq $GR 1.0))
  );progn
);if
(initget 1)
(setq $P2 (getpoint  $P1 "\nProjected Point: "))
;
; #################  Calculation  #################
;
(while $P2
(setq $D1-2 (distance $P1 $P2))

(if (= units 1000.0)
  (setq $DIFF (/ (* $D1-2 (/ $GR 100.0)) 1000.0))
  (setq $DIFF (* $D1-2 (/ $GR 100.0)))
)
(setq $LUP (+ $l1 $DIFF))
(princ (strcat "\n.. START PT RL = " (rtos $L1 2 3) "m"))
(princ (strcat " ..SLOPE BETWEEN PTS = " (rtos $GR 2 3) "%"))
(princ (strcat "\n.. DIST BETWEEN PTS = " (rtos $D1-2 2 3) "m"))
(princ (strcat ".. HEIGHT DIFF = " (rtos $DIFF 2 3) "m"))
(princ (strcat "\n.. EXTRAPOLATED RL IS = " (rtos $LUP 2 3) "m"))


(setq INSRL (getstring "\nINSERT RL CROSS? Y/N <N>: "))
(if (/= INSRL "")(setq INSRL (strcase (substr INSRL 1 1))))
(if (= INSRL "Y")
(PROGN
(SETVAR "ATTDIA" 0)
(SETVAR "INSUNITS" 0)
(setq insscl (* 1 (getvar "dimscale")))
(COMMAND "-LAYER" "M" "RLCROSS" "C" 2 "" "")
(COMMAND "-insert" "RLCROSS" "_S" insscl $P2 "0" (rtos $LUP 2 3))
(command "-layer" "M" "VP" "C" "6" "VP" "P" "N" "VP" "" "line" $P1 $P2 "")
(setvar "clayer" oldlay)
(SETVAR "ATTDIA" 1)

)
)

(setq $P2 (getpoint  $P1 "\nProjected Point: "))
);while
(princ)
); defun EXTRA

 

You will also need the attached DWG of the rl to be within your acad search path.

 

Thnak guys

RLCROSS.dwg

[alanjt]

setq a new point with this sub:

;(mid3dpt pt1 pt2)
(defun mid3dpt (pt1 pt2 /)
 (setvar
   "lastpoint"
   (mapcar '+
           pt1
           (mapcar '/ (mapcar '- pt2 pt1) '(2.0 2.0 2.0))
   )
 )
 "@" ;;;; will display "@" after midpoint is calced, remove this line to display coordinates of calced midpoint
)

(setq $p_mid (mid3dpt $p1 #p2))

[CAB]

Another method:

;; Returns the middle of two points
(defun mid-pt (p1 p2)
 (polar p1 (angle p1 p2) (/ (distance p1 p2) 2.) )
)

[russell84]

nice couple of methods guy.

 

thanks for your help.

 

one quick one

 

how do you get an offset point fom the mid point if i wanted to insert some text say 2.5 x dimscale offset from the midpoint

[VovKa]

And another another method

(defun GetMidPoint
	      (p1 p2)
 (mapcar (function (lambda (e1 e2) (/ (+ e1 e2) 2.))) p1 p2)
)

[Lee Mac]

how do you get an offset point fom the mid point if i wanted to insert some text say 2.5 x dimscale offset from the midpoint

 

Try this maybe:

(defun c:txtoff (/ offs l1 l1ent p1 p2 l1ang txt txtpt txtpt1)
 (setq offs (getreal "\nSpecify Offset Distance: "))
 (while
   (/= (setq l1 (car (entsel "\nSelect Line for Text: "))) nil)
   (setq l1ent (entget l1))
   (setq p1 (cdr (assoc 10 l1ent)))
   (setq p2 (cdr (assoc 11 l1ent)))
   (setq l1ang (angle p1 p2))
   (setq txt (getstring t "\nSpecify Text: "))
   (setq txtpt
       (polar
           p1
           l1ang
           (/ (distance p1 p2) 2)
       ) ; end polar
   ) ; end setq
   (setq txtpt1
       (polar
           txtpt
           (+ l1ang (/ pi 2))
           offs
       ) ; end polar
   ) ; end setq
   (entmake    (list    '(0 . "TEXT")
               '(8 . "TEXT")
               (cons 10 txtpt1)
               (cons 40 (* 2.5 (getvar "DIMSCALE")))
               (cons 1 txt)
               (cons 50 l1ang)
               '(7 . "STANDARD")
               '(71 . 0)
               '(72 . 1)
               '(73 . 2)
               (cons 11 txtpt1)
           ) ; end list
   ) ; end entmake    
 ) ; end while
 (princ)
) ; end program

[Soumen]

There are say, 50 points with diferrent x,y in my screen.

First step : I want to indicate the points from which mid points will be measured.

Second step: I need to define a search radius; a circle can be imagined from those selected points in step 1

Third: within that circle i need to idntify other points with x,y and created mid points from that selected points for each pair

These mid points can be joined by a closed polygon.

 

Can anyone help please?