Lisp to draw spline, get P1 & P2 coordinates

[Arepo]

I was wondering if someone could help me with a lisp to draw a spline and get the coordinates of the first two points of the spline. I need them to insert a block in the first point of the spline and to define the angle between the points.

I started with the lisp below but I can't make it work properly, the command prompts are different from the prompts for the standard AutoCAD spline, it promts for and . I have to hit ENTER a few times to exit the program.

I am using AutoCAD 2011.

Thank you.

 

 

(defun c: DrawSpline ()
  (command "._spline")
  (while (> (getvar "cmdactive") 0)
  (command pause)
)

Edited June 22, 2012 by Arepo

[Lee Mac]

Consider the following code:

 

(defun c:DrawSpline ( / a e p )
   (setq e (entlast))
   (initcommandversion)
   (command "._spline")
   (while (< 0 (getvar 'cmdactive))
       (command pause)
   )
   (if (not (eq e (setq e (entlast))))
       (progn
           (setq p (vlax-curve-getstartpoint e)
                 a (angle '(0.0 0.0 0.0) (vlax-curve-getfirstderiv e (vlax-curve-getstartparam e)))
           )
       )
   )
   (princ)
)
(vl-load-com) (princ)

 

In the above example, variable 'p' is the start point of the Spline, variable 'a' is the angle of the tangent at the start point.

 

I would also suggest you read the Code Posting Guidlines regarding formatting code in your posts.

[Tharwat]

Maybe ....

 

(defun c:Test (/ p1 p2)
 (if (and (setq p1 (getpoint "\n First point :"))
          (setq p2 (getpoint "\n Second point :" p1))
     )
   (command "_.spline" "_non" p1 "_non" p2)
   (while (> (getvar 'cmdactive) 0)
     (command pause)
   )
 )
 (princ)
)

[SLW210]

Arepo,

 

Please read the CODE POSTING GUIDELINES and edit your posts.

[Lee Mac]

Thank you, Lee Mac. Works perfectly (no idea how you avoided those annoying prompts though ) I used

(/ (* a 180) PI)

to calculate the insertion angle for the block.

 

You're very welcome Arepo

 

The prompts are altered by the use of the initcommandversion function, which initialises a command to a specific (or the latest) version.

[aloy]

Hi Tharwat,

Is it possibe to extend your code to draw three seperate lines: p1 p2, p3 p4 and another line from intersection of these two lines to a fifth point, while allowing for zoom window before getting the points and zoom previous each time after getting the point?. There is a Road Design application for this.

Regards,

Aloy

[Tharwat]

Hi Tharwat,

Is it possibe to extend your code to draw three seperate lines: p1 p2, p3 p4 and another line from intersection of these two lines to a fifth point, while allowing for zoom window before getting the points and zoom previous each time after getting the point?. There is a Road Design application for this.

Regards,

Aloy

 

How the code to draw three separate lines and another line from intersection on these tow lines ???

 

Can you explain your goal in more details please ?

 

You want normal lines of spline ?

[Lee Mac]

???

 

(defun c:test ( / ip p1 p2 p3 p4 p5 )
   (if
       (and
           (setq p1 (getpoint "\n1st Point: "))
           (setq p2 (getpoint "\n2nd Point: " p1))
           (setq p3 (getpoint "\n3rd Point: "))
           (setq p4 (getpoint "\n4th Point: " p3))
       )
       (if (setq ip (inters p1 p2 p3 p4 nil))
           (if (setq p5 (getpoint "\n5th Point: " ip))
               (mapcar
                   (function
                       (lambda ( a b )
                           (entmake
                               (list
                                  '(0 . "LINE")
                                   (cons 10 (trans a 1 0))
                                   (cons 11 (trans b 1 0))
                               )
                           )
                       )
                   )
                   (list p1 p3 ip)
                   (list p2 p4 p5)
               )
           )
           (princ "\nLines are Parallel.")
       )
   )
   (princ)
)

[aloy]

LeeMac,

Thank you very much. The code works to get the three lines. Actually the third line is on the bisector of angle between the first two lines. However I need to zoom in on the areas covering the five points before giving them on command and need to zoom out also each time after giving the point.

Tharwat,

My aim is to give these points on a corridoor survey drawing loaded in AutoCAD and calculate the optimum radius of the circular curve, the optimum length of transition curve (which is a spiral or clothoid) to suit the super elevation within limits and driving comfort depending on the type of road to the design speed, by iteration, all according to the design standards of the country where the road project is to be implemented.

Regards,

Aloy

Edited June 24, 2012 by aloy