Forward Visibility Lisp - DXF issue

[CivilTechSource]

Hi I found this Forward Visibility Lips online but it was drawing the forward vis line slightly wrong so I have modified it now. It works okay, but when I was debugging it at the end of the routine it would through an error message (See image). The lisp however does complete everything as required apart from setting Layer 0 at the end. I am looking to address that error.

(vl-load-com)
(defun C:CTS-ForwardVis ()
	;Set the Layer for the New Polylines
  (if (not (tblsearch "LAYER" "CTS-Forward Visibility")) 
    (command "-LAYER" "_M" "CTS-Forward Visibility" "_C" "True" "255,100,0" "CTS-Forward Visibility" "" ""))
  (command "clayer" "" "CTS-Forward Visibility" "")
  
  ; Predefined variables
  (setq ForwardVisDistance 15.0)    ; Default forward visibility distance
  (setq inc 2.0)        ; Default increment/resolution
  
  ; Prompt user to accept/change defaults
  (initget "Yes No")
  (if (= (getkword (strcat "\nUse default settings? [Yes/No] <Yes>: ")) "No")
    (progn
      (setq ForwardVisDistance (getdist (strcat "\nEnter default visibility distance <" (rtos ForwardVisDistance 2 2) ">: ")))
      (setq inc (getdist (strcat "\nEnter default increment/resolution <" (rtos inc 2 2) ">: ")))
    )
  )
  
  (princ (strcat"\nSelect Polyline:"))
	(while
		(not
			(setq js
				(ssget "_+.:E:S" 
					(list
						(cons 0 "*POLYLINE,ARC,SPLINE")
						(cons 67 (if (eq (getvar "CVPORT") 2) 0 1))
						(cons 410 (if (eq (getvar "CVPORT") 2) "Model" (getvar "CTAB")))
						(cons -4 "<NOT")
							(cons -4 "&") (cons 70 112)
						(cons -4 "NOT>")
					)
				)
			)
		)
	)
  
  ;----- Assign the Selected Polyline to a VLA-Object and get its Length and other properties
	(setq
		SelPline (vlax-ename->vla-object (ssname js 0))
		SelPline_Length (vlax-curve-getDistAtParam SelPline (vlax-curve-getEndParam SelPline))
    Counter 0.0
    SPoint nil
    EPoint nil
  )
  
  ;----- Check Forward Visi Distance and Increment against the Length of the Selected Polyline
  (while (>= ForwardVisDistance SelPline_Length)
    (if (>= ForwardVisDistance SelPline_Length) (princ "\nDistance execeded length of Selected Polyline"))
  )
  (while (>= inc SelPline_Length)
    (if (>= inc SelPline_Length) (princ "\nDistance execeded length of Selected Polyline"))
  )
  
  ;----- Function to create Forward Visibility Polylines
	(while (< Counter SelPline_Length)
		(setq EPoint (vlax-curve-getPointAtDist SelPline (+ Counter ForwardVisDistance)))
    (setq SPoint (vlax-curve-getPointAtDist SelPline Counter))
    (entmake
      (append
        '(
          (0 . "LWPOLYLINE")
          (100 . "AcDbEntity")
          (67 . 0)
          (410 . "Model")
          (8 . "CTS-Forward Visibility")
          (62 . 256)
          (6 . "ByLayer")
          (370 . -2)
          (100 . "AcDbPolyline")
          (90 . 2)
        )
        (list (cons 10 SPoint))
        (list (cons 10 EPoint))
        '((210 0.0 0.0 1.0))
      )
    )
   
    (setq SPoint (vlax-curve-getPointAtDist SelPline (+ Counter inc)))
    (setq Counter (+ Counter inc))
	)
    (command "clayer" "" "0" "")
)

 

Thank you!!

[Steven P]

Sounds like on the last run through the while loop SPoint is having an error... if you look at (setq SPoint (vlax-curve-getPointAtDist SelPline (+ Counter inc))) - do you need this line since at the start of the next loop you are setting SPoint again and before it is used.

[GLAVCVS]

Hi

Like @Stevenp, I can't verify exactly what this is about either: I'm not in front of a PC. But it looks like the last SPoint is 'nil' because '(+ Counter ForwardVisDistance)' is a number greater than the length of 'selPline'.

There are a few lines of code that are unnecessary, but they don't prevent your routine from working, so just try changing
(while (< Counter SelPline_Length)
to

(while (and (setq EPoint (vlax-curve-getPointAtDist SelPline (+ Counter ForwardVisDistance))) (setq SPoint (vlax-curve-getPointAtDist SelPline Counter)))

 

It looks like you used AI to do this, but you should still be able to remove the excess code after making these changes.

 

[BIGAL]

Ignoring the code for the moment, "Civil Site Design" has check site lines and it checks against the terrain model and the vertical alignment, not just a 2D answer. Looks at the drivers eye height and target height which is part of the check for us here in AUS.