Topic: VLA-INTERSECTWITH Question

[Peter Guappa]

To find the intersection of a polyline and a virtual line (not in dwg), I "entmake" a temporary line , get the intersection with vla-intersectwith and "entdel" the temporary line.

Are there other/better options to do this? Because when the user presses the escape-button before the routine terminates, these temporary lines remain in the dwg.

[Lee Mac]

Are there other/better options to do this?

You could use the inters function with each segment of the polyline, however, this would only work with straight-segmented polylines.

A quick example of such a function might be:

Code - Auto/Visual Lisp: [Select]

1. (defun _polyinters ( en p1 p2 / vl )
2.     (setq en (entget en)
3.           vl (mapcar 'cdr (vl-remove-if-not '(lambda ( x ) (= 10 (car x))) en))
4.     )
5.     (vl-remove-if 'null
6.         (mapcar '(lambda ( p3 p4 ) (inters p1 p2 p3 p4))
7.             vl
8.             (if (= 1 (logand 1 (cdr (assoc 70 en))))
9.                 (append (cdr vl) (list (car vl)))
10.                 (cdr vl)
11.             )
12.         )
13.     )
14. )

Code - Auto/Visual Lisp: [Select]

1. (_polyinters <LWPolyline-entity> <point1> <point2>)

Because when the user presses the escape-button before the routine terminates, these temporary lines remain in the dwg.

You could easily incorporate an error handler (a redefined *error* function) to erase the temporary lines should the user press Esc. I have written a short tutorial on this topic here.

[Peter Guappa]

So, the best thing I can do is entmake the line in a layer with a unique name like "9A9A9A9A9A9A9A9A9A9A9A9A9A9A9A9A9A"

and in the *error* do a ssget "x" on that layer, erase the selectionset and purge the layer?

[Lee Mac]

So, the best thing I can do is entmake the line in a layer with a unique name like "9A9A9A9A9A9A9A9A9A9A9A9A9A9A9A9A9A"

and in the *error* do a ssget "x" on that layer, erase the selectionset and purge the layer?

No, just entdel the entity name in the *error* function, if it exists and is unerased.

[Peter Guappa]

That would be easier   
I should get some sleep....

[CAB]

A word of Caution, if the item has been deleted the entdel will restore it to the drawing.

Consider (vlax-erased-p obj)

[Lee Mac]

A word of Caution, if the item has been deleted the entdel will restore it to the drawing.

Consider (vlax-erased-p obj)

Or (entget <entity>) for enames.