make & call subfunction with parameter / shorten line at start and end

hi all.

i wonder if anybody can tell me how I can put the following code into a sub-function, so that i can call it several times in the main function.

the idea is to pass a polyline / entity together with one parameter that defines the trimming length on both ends of the polyline. it should return the trimmed polyline.

here's the code i have:

; active object
(setq myline (entlast))
 
; trip distance
(setq trim_dist 50)

; First Break Point Sets
(setq start_point (vlax-curve-getPointAtDist myobj 0))
(setq trim_point (vlax-curve-getPointAtDist myobj trim_dist))

; First Break
(command "._break" myline "_non" (trans start_point 0 1) "_non" (trans trim_point 0 1))

(setq myline (entlast))

; Second Break Point Sets
(setq edpt (vlax-curve-getendparam myline))
(setq el_length (vlax-curve-getDistAtParam myline edpt)) ; length of element
(setq trim_point2 (vlax-curve-getPointAtDist myline (- el_length trim_dist)))
(setq end_point (vlax-curve-getPointAtDist myline el_length))

; Second Break
(command "._break" myline "_non" (trans end_point 0 1) "_non" (trans trim_point2 0 1))

; Result
(setq result_line (entlast))

I believe this is what you were looking for:

[color=magenta](defun TrimPline( myline trim_dist[/color]
[color=magenta]                / start_point trim_point edpt el_length trim_point2 end_point )[/color]
; First Break Point Sets
(setq start_point (vlax-curve-getPointAtDist [color=red]myline[/color] 0))
(setq trim_point (vlax-curve-getPointAtDist [color=red]myline[/color] trim_dist))

; First Break
(command "._break" myline "_non" (trans start_point 0 1) "_non" (trans trim_point 0 1))

; Second Break Point Sets
(setq edpt (vlax-curve-getendparam myline))
(setq el_length (vlax-curve-getDistAtParam myline edpt)) ; length of element
(setq trim_point2 (vlax-curve-getPointAtDist myline (- el_length trim_dist)))
(setq end_point (vlax-curve-getPointAtDist myline el_length))

; Second Break
(command "._break" myline "_non" (trans end_point 0 1) "_non" (trans trim_point2 0 1))

; Result
[color=red] myline[/color]
[color=magenta])[/color]

[color=magenta](while (setq ssetPline (ssget "_:S" '((0 . "LWPOLYLINE"))))[/color]
[color=magenta] (TrimPline (ssname ssetPline 0) 50.0)[/color]
[color=magenta])[/color]

Please note that I have made some other correction to your code; you need also to add some validations to don't exceed polyline's length with the trim size.

thanks Mircea,

I think this goes into the right direction.

allow me to be more concrete, in my main script, i will create a polyline (boundary) and explode it. I want to pass the exploded segments of this boundary to this subfunction to shorten all of them.

martin

I believe this is what you were looking for:

[color=magenta](defun TrimPline( myline trim_dist[/color]
[color=magenta]                / start_point trim_point edpt el_length trim_point2 end_point )[/color]
; First Break Point Sets
(setq start_point (vlax-curve-getPointAtDist [color=red]myline[/color] 0))
(setq trim_point (vlax-curve-getPointAtDist [color=red]myline[/color] trim_dist))

; First Break
(command "._break" myline "_non" (trans start_point 0 1) "_non" (trans trim_point 0 1))

; Second Break Point Sets
(setq edpt (vlax-curve-getendparam myline))
(setq el_length (vlax-curve-getDistAtParam myline edpt)) ; length of element
(setq trim_point2 (vlax-curve-getPointAtDist myline (- el_length trim_dist)))
(setq end_point (vlax-curve-getPointAtDist myline el_length))

; Second Break
(command "._break" myline "_non" (trans end_point 0 1) "_non" (trans trim_point2 0 1))

; Result
[color=red] myline[/color]
[color=magenta])[/color]

[color=magenta](while (setq ssetPline (ssget "_:S" '((0 . "LWPOLYLINE"))))[/color]
[color=magenta] (TrimPline (ssname ssetPline 0) 50.0)[/color]
[color=magenta])[/color]

Please note that I have made some other correction to your code; you need also to add some validations to don't exceed polyline's length with the trim size.

In this case call the function above like this:

(setq basePLine (entlast))
;explode the polyline and parse resulted selection set
(command "_.EXPLODE" basePLine)
(setq ssetLines (ssget "_P"))

(while (> (sslength ssetLines) 0)
(setq myline (ssname ssetLines 0))     ;process first item in selection set
([b]TrimPline[/b] myline 5)

(setq ssetLines (ssdel myline ssetLines))   ;remove processed item
)

mircea,

understood - thanks for your help!

now i can continue to work on re-connecting the trimmed segments with straight lines and re-join them into a polyline. (practically replacing chamfer to work for all linetypes...)

martin

In this case call the function above like this:

(setq basePLine (entlast))
;explode the polyline and parse resulted selection set
(command "_.EXPLODE" basePLine)
(setq ssetLines (ssget "_P"))

(while (> (sslength ssetLines) 0)
(setq myline (ssname ssetLines 0))     ;process first item in selection set
([b]TrimPline[/b] myline 5)

(setq ssetLines (ssdel myline ssetLines))   ;remove processed item
)

Not sure why you want to achive exactly; are you aware that may apply the CHAMFER command a polyline like this?

 (setvar "CHAMFERA" 5.0)
(setvar "CHAMFERB" 5.0)
(command "_.CHAMFER" "_P" (entlast))

For sure, a good programming practice will be to retain user’s chamfer distances and replace them after processing.

Regarding the appearance of non-continuous line types on polyline please check the Ltype gen option of PLINE command.

CHAMFER is not working if the polyline contains arc segments, that's why i would like to explode it and draw them via a lisp routine.