Topic: Help with intersection

[velasquez]

I have a list with two points that intersect one polyline, how to find the point of intersection?
I can not work with vla-intersectwith because I only have one entity.

[CAB]

Create a temporary entity.

[velasquez]

I have a list with two points that intersect one polyline, how to find the point of intersection?
I can not work with vla-intersectwith because I only have one entity.

Hello Cab,
This is my problem that happens in a while.
I want to avoid the creation of many temporary entities.
Thanks

[T.Willey]

You can step through the vertices of the polyline, and use the built in Lisp function 'inters' with the four points ( two from the polyline, per segment, and the two you show as yellow in your image ) you have.

[Kerry]

Or you could do something like this :

Code - Auto/Visual Lisp: [Select]

1. (defun c:doit (/ catchit intersectionpoint obj1 p1 p2 templine)
2.    ;; Codehimbelonga kdub 2015/07/16
3.    ;; Proof of concept code
4.  
5.    (if (and
6.           (setq p1 (getpoint "Select First Point"))
7.           (setq p2 (getpoint p1 "Select Second Point"))
8.  
9.           (setq obj1 (entsel))
10.           (setq obj1 (car obj1))
11.  
12.           (setq tempLine
13.                   (vla-addline
14.                      (kdub:activespace)
15.                      (vlax-3d-point p1)
16.                      (vlax-3d-point p2)
17.                   )
18.           )
19.        )
20.       (setq catchit (vl-catch-all-apply
21.                        'vla-intersectwith
22.                        (list tempLine
23.                              (vlax-ename->vla-object obj1)
24.                              acextendboth
25.                        )
26.                     )
27.       )
28.    )
29.    (if tempLine
30.       (vla-delete tempLine)
31.    )
32.    (if (and catchit (not (vl-catch-all-error-p catchit)))
33.       (alert (vl-princ-to-string
34.                 (setq IntersectionPoint (kdub:lisp-value catchit))
35.              )
36.       )
37.       (alert "Oooops")
38.    )
39.  
40.  
41.    (princ)
42. )
43.  

LIBRARY STUFF

Code - Auto/Visual Lisp: [Select]

1. ;; (setq *:acapp nil *:activedoc nil *:modelspace nil *:paperspace nil)
2. ;;;; IAcadApplication Object
3. (or *:acapp (setq *:acapp (vlax-get-acad-object)))
4.  
5. ;;;; IAcadDocument Object
6. (or *:activedoc
7.     (setq *:activedoc (vla-get-activedocument *:acapp))
8. )
9.  
10. ;;;; IAcadModelSpace Object
11. (or *:modelspace
12.     (setq *:modelspace (vla-get-modelspace *:activedoc))
13. )
14.  
15. ;;;; IAcadPaperSpace Object
16. (or *:paperspace
17.     (setq *:paperspace (vla-get-paperspace *:activedoc))
18. )
19.  
20. ;;--------------------------------------------------------------
21. ;;--------------------------------------------------------------
22. (defun kdub:activespace ()
23.    (if (= acmodelspace (vla-get-activespace *:activedoc))
24.       *:modelspace
25.       (if (= :vlax-true (vla-get-mspace *:activedoc))
26.          *:modelspace
27.          (vla-get-paperspace *:activedoc)
28.       )
29.    )
30. )
31. ;;--------------------------------------------------------------
32. ;;; lisp-value : Author : Vladimir Nesterovsky 2002
33. (defun kdub:lisp-value (val)
34.    (cond
35.       ((= (type val) 'variant) (kdub:lisp-value (variant-value val)))
36.       ((= (type val) 'safearray)
37.        (mapcar 'kdub:lisp-value (safearray-value val))
38.       )
39.       (t val)
40.    )
41. )
42. ;;--------------------------------------------------------------
43.  

[roy_043]

@ Kerry: Can you explain this:

Code - Auto/Visual Lisp: [Select]

1. ;;;; IAcadApplication Object
2. (or *:acapp (vlax-get-acad-object))

Shouldn't there be a setq somewhere?

[Kerry]

@ Kerry: Can you explain this:

Code - Auto/Visual Lisp: [Select]

1. ;;;; IAcadApplication Object
2. (or *:acapp (vlax-get-acad-object))

Shouldn't there be a setq somewhere?

Yes there should.
I usually do the assignment  to a protected variable ... mucked up the edit for here.

Will fix shortly ...
Thanks for the sharp eye.

[Lee Mac]

You can step through the vertices of the polyline, and use the built in Lisp function 'inters' with the four points ( two from the polyline, per segment, and the two you show as yellow in your image ) you have.

1+

Here's an example:
http://www.theswamp.org/index.php?topic=43630.msg489026#msg489026

[velasquez]

You can step through the vertices of the polyline, and use the built in Lisp function 'inters' with the four points ( two from the polyline, per segment, and the two you show as yellow in your image ) you have.

Hello and thank you Lee,
I do not have a straight polyline the points that I have not intersect.
I need to work with (inters p1 p2 p3p4 nil) to extend.
I'll try the suggestion of T.Willey to go through the vertices of the polyline looking for the intersection.
Do you have any suggestion?...

[velasquez]

Code: [Select]

[quote author=Kerry link=topic=49763.msg549263#msg549263 date=1437025132]
Or you could do something like this :

Thank you Kerry,
But I can not create a temporary line.

   

[Kerry]

You can not
or you will not ?

[velasquez]

You can not
or you will not ?

Hello Kerry,
I do not informed well, I should not interrupt the work of a function to create a temporary entity and then delete it, as it may happen thousands of times. I already have a polyline selected in beginning the work of a function.

[Kerry]

You can not
or you will not ?

Hello Kerry,
I do not informed well, I should not interrupt the work of a function to create a temporary entity and then delete it, as it may happen thousands of times. I already have a polyline selected in beginning the work of a function.

You don't need to interrupt anything or do anything manually.

Have you tried the code or looked at how it works ??

The line is drawn and erased when finished by the program ... I doubt you will actually ever see it.

The code is just proof of concept to demonstrate the functionality. I doesn't matter if you select the points and line or if they are provided programmatically ; the methodology still works.

For production code I'd produce a standalone function that takes the pline object and the 2 points as parameters and returns either the intersection point of nil, as applicable. This way it can be called from either an interactive or programmatic situation.

Regards,
 

[velasquez]

You can not
or you will not ?

Hello Kerry,
I do not informed well, I should not interrupt the work of a function to create a temporary entity and then delete it, as it may happen thousands of times. I already have a polyline selected in beginning the work of a function.

You don't need to interrupt anything or do anything manually.

Have you tried the code or looked at how it works ??

The line is drawn and erased when finished by the program ... I doubt you will actually ever see it.

The code is just proof of concept to demonstrate the functionality. I doesn't matter if you select the points and line or if they are provided programmatically ; the methodology still works.

For production code I'd produce a standalone function that takes the pline object and the 2 points as parameters and returns either the intersection point of nil, as applicable. This way it can be called from either an interactive or programmatic situation.

Regards,
 

Many thanks Kerry,
Your code works perfectly.

[mianbaoche]

   (defun c:tt()
   (princ "\nPlease select LWPOLYLINE")(setq en (car(entsel)))
   (princ "\nPlease selectLINE")(setq e1(entget (car(entsel))))
  (foreach a (_polyinters en (cdr (assoc 10 e1)) (cdr (assoc 11 e1)))  (entmakex (list (cons 0 "CIRCLE")(cons 10 a)(cons 40 40))))
 (princ) )

(defun _polyinters ( en p1 p2 / vl l ang)
    (setq en (entget en)
          vl (mapcar 'cdr (vl-remove-if-not '(lambda ( x ) (= 10 (car x))) en))
          l (distance (apply 'mapcar (cons 'min vl)) (apply 'mapcar (cons 'max vl)))
     ang (angle p1 p2)
     )
    (vl-remove-if 'null
        (mapcar '(lambda ( p3 p4 ) (inters (polar p1 ang l) (polar p2 (+ ang pi) l) p3 p4))
            vl
            (if (= 1 (logand 1 (cdr (assoc 70 en))))
                (append (cdr vl) (list (car vl)))
                (cdr vl)
            )
        )
    )
)