Vertices of polyline near a point

[rog1n]

Hello, I have a polyline with many vertices, I can find the closest point [red X] of this polyline with other point [blue X] with vlax-curve-getClosestPointTo as the image bellow, but how I find the two vertices [red circles] that represent the line segment of the red X?

[dlanorh]

Use

 (setq p_param (vlax-curve-getparamatpoint ent (red cross coords)))

this will return the polyline parameter at that point (each vertex is a whole number parameter)

 

Then

(setq pre_param (fix p_param)   ;the parameter of the vertex before
	  post-param (1+ pre_param) ;the vertex after
	  pre_vtx (vlax-curve-getpointatparam ent pre_param)   ;gets the coords of the vertex before
	  post_vtx (vlax-curve-getpointatparam ent post_param) ;the coords of the vertex after
)

 

Edited October 7, 2019 by dlanorh

[rog1n]

Thank you dlanorth, worked! 

[dlanorh]

No problem.

 

You could run them together, but you start to lose readability

 

 (setq p_param (vlax-curve-getparamatpoint ent closest-pt-on-pline ))


(setq pre_vtx (vlax-curve-getpointatparam ent (fix p_param))       ;gets the coords of the vertex before
      post_vtx (vlax-curve-getpointatparam ent (1+ (fix p_param))) ;the coords of the vertex after
)