Topic: How to find if there is a coordinate point between two points on polyline

[Coder]

Hello guys.

I am having a hard time to find if there is a coordinate point between the two points placed on a polyline and I have attached an image showing the problem in more details.

How can I get the coordinate point of a Polyline that is placed between the two points ( p1  p2 ) otherwise return nil if not found.

I hope also if the codes can find if there are more than one coordinate in some situations.

Code: [Select]

(setq poly (car (entsel "\nSelect polyline :")))
(setq p1 (vlax-curve-getpointatdist poly 0.5))
(setq p2 (vlax-curve-getpointatdist poly 1.5))

Thanks in advance.

[Lee Mac]

Here is an easy way, but is dependent on the parameterisation of the polyline:

Code - Auto/Visual Lisp: [Select]

1. (defun vertexbetween-p ( ent pt1 pt2 )
2.     (/= (fix (vlax-curve-getparamatpoint ent pt1))
3.         (fix (vlax-curve-getparamatpoint ent pt2))
4.     )
5. )

Here is another way:

Code - Auto/Visual Lisp: [Select]

1. (defun vertexbetween-p ( ent pt1 pt2 / di1 di2 tmp )
2.     (setq di1 (vlax-curve-getdistatpoint ent pt1)
3.           di2 (vlax-curve-getdistatpoint ent pt2)
4.           tmp (min di1 di2)
5.           di2 (max di1 di2)
6.           di1 tmp
7.     )
8.     (vl-some '(lambda ( x ) (< di1 (vlax-curve-getdistatpoint ent (trans (cdr x) ent 0)) di2))
9.         (vl-remove-if-not '(lambda ( x ) (= 10 (car x))) (entget ent))
10.     )
11. )

Additionally testing may be required to account for closed polylines.

Both of the above are untested.

[Coder]

Many thanks Lee , that is prefect.