How to get the the coordinates of blocks ?

[yxl030]

If the base point of  block is not in the block，how to get the coordinates of it?
As other people will use these diagrams, I can't change the base point.

I wrote a lisp, but there are sometimes it's  correct and sometimes it's not.

 

(defun c:test()
 (setq BasePoint (list -34.80394906 16.72215194)) ;;the Offset coordinates from 0,0 
 (print "select the block1")        ;; this is correct
 (setq ss (ssget '((0 . "INSERT"))))
 (repeat (setq i (sslength ss))
 (setq px (cdr (assoc 10 (entget (ssname ss (setq i (1- i)))))))
 (setq blkAng (cdr (assoc 50 (entget (ssname ss i)))))
 (setq sx (cdr (assoc 41 (entget (ssname ss i)))))
 (setq sy (cdr (assoc 42 (entget (ssname ss i)))))
   (print sx) (print sy)
 (setq p0 (blkCo px blkAng BasePoint sx sy))
 (command "line" p0 '(0 0) "")
 )                                     

 (setq BasePoint (list  -628.69148552 795.40681600))
    (print "select the block2")         ;; this is not  
 (setq ss (ssget '((0 . "INSERT"))))
 (repeat (setq i (sslength ss))
 (setq px (cdr (assoc 10 (entget (ssname ss (setq i (1- i)))))))
 (setq blkAng (cdr (assoc 50 (entget (ssname ss i)))))
 (setq sx (cdr (assoc 41 (entget (ssname ss i)))))
 (setq sy (cdr (assoc 42 (entget (ssname ss i)))))
   (print sx) (print sy)
 (setq p0 (blkCo px blkAng BasePoint sx sy))
 (command "line" p0 '(0 0) "")
 )
 )

(defun blkCo(blkInsert blkAng BasePoint sx sy / p0 px py )
 (setq px (* (car BasePoint) sx))
 (setq py (* (cadr BasePoint) sy))
 (setq p0x (- (car blkInsert) (- (* (cos blkAng) px) (* (sin blkAng) py))))
 (setq p0y (- (cadr blkInsert) (+ (* (cos blkAng) py) (* (sin blkAng) px))))
 (setq p0 (list p0x p0y))
 )

 

And Is there a better way to do this?

Drawing1.dwg

[michael256]

to set the block base point to 0,0 I would just open the block in the editor then select all, start move command, then select what you want the new base point to be and type 0,0. 

[zwonko]

Maybe this will be help for You:

http://www.lee-mac.com/changeblockinsertion.html

[yxl030]

michael256, zwonko, thank you for your reply, Modifying blocks will affect other people.
lee-mac 's lisp is great. I use it a lot

[michael256]

Sorry I obviously didn't read the question properly before replying 

[lrm]

I'm not sure exactly what you want to do but nentsel may be of help.

 

(defun c:test2 ()
  (princ "\nSelect the block")
  (setq blkdata (nentsel))
  (setq Tmatrix (nth 2 blkdata))
  (setq blk_pt (nth 3 Tmatrix))
  (command "_point" blk_pt)
  (princ "\nBase point = ")
  (princ blk_pt)
  (setq ang (/ (* 180.0 (angle '(0 0 0) (nth 0 Tmatrix))) pi))
  (princ "\nAngle = ")
  (princ ang)
  (setq xscale (distance '(0 0 0) (nth 0 Tmatrix)))
  (setq yscale (distance '(0 0 0) (nth 1 Tmatrix)))
  (princ "\nX scale = ")
  (princ xscale)
  (princ "\nY scale = ")
  (princ yscale)
  (princ)
)

 

[yxl030]

lrm,Thank you.
Sorry for my late response. I later learned that the units of a block also affect position conversion