;;;   Designed and implemented by Kelvin R. Throop in January 1985
;;;
;;;   This program constructs a spiral. It can be loaded and called 
;;;   by typing either "spiral", "3dspiral" or the following:
;;;   (cspiral <# Umdrehungen> <Basispunkt> <Horizontaler Zuwachs pro Umdrehung>
;;;            <Punkte pro Umdrehung> <Start Radius> 
;;;            <Vertikaler Zuwachs pro Umdrehung>).
;;;
;;; --------------------------------------------------------------------------;

(defun myerror (s)                    ; If an error (such as CTRL-C) occurs
                                      ; while this command is active...
  (if (/= s "Function cancelled")
    (princ (strcat "\nError: " s))
  )
  (setvar "cmdecho" ocmd)             ; Restore saved modes
  (setvar "blipmode" oblp)
  (setq *error* olderr)               ; Restore old *error* handler
  (princ)
)


(defun cspiral (ntimes bpoint hfac lppass strad vfac / ang dist tp ainc dhinc dvinc circle dv)
   (setvar "blipmode" 0)               ; turn blipmode off
  (setvar "cmdecho" 0)                ; turn cmdecho off
  (setq circle (* pi 2))
  (setq ainc (/ circle lppass))
  (setq dhinc (/ hfac lppass))
  (if vfac (setq dvinc (/ vfac lppass)))
  (setq ang 0.0)
  (if vfac
    (setq dist strad dv 0.0)
    (setq dist 0.0)
  )
  (if vfac 
    (command "_3dpoly")                ; start spiral ...
    (command "_pline" bpoint)         ; start spiral from base point and...
  )
  (repeat ntimes 
    (repeat lppass 
      (setq tp (polar bpoint (setq ang (+ ang ainc))
                      (setq dist (+ dist dhinc))
               )
      )
      (setq dv (+ dv dvinc))
      (if vfac (setq tp (list (car tp) (cadr tp) (+ dv (caddr tp)))))
      (command tp)                    ; continue to the next point...
    )
  ) 
  (command "")                        ; until done.
  (princ)
) 

;;;
;;;       Interactive spiral generation
;;;

(defun C:SPIRAL (/ olderr ocmd oblp nt bp cf lp) 
  ;;;;(setq olderr  *error*
  ;;;;      *error* myerror)
  (setq ocmd (getvar "cmdecho"))
  (setq oblp (getvar "blipmode"))
  (setvar "cmdecho" 0)
  (initget 1)                         ; bp must not be null
  (setq bp (getpoint "\nMittelpunkt: "))
  (initget 7)                         ; nt must not be zero, neg, or null
  (setq nt (getint "\nAnzahl der Umdrehungen: "))
  (initget 3)                         ; cf must not be zero, or null
  (setq cf (getdist "\nZuwachs pro umdrehung: "))
  (initget 6)                         ; lp must not be zero or neg
  (setq lp (getint "\nPunkte oro Umdrehung <30>: "))
  (cond ((null lp) (setq lp 30))) 
  (cspiral nt bp cf lp nil nil)
  (setvar "cmdecho" ocmd)
  (setvar "blipmode" oblp)
  (setq *error* olderr)               ; Restore old *error* handler
  (princ)

) 

;;;
;;;       Interactive spiral generation
;;;

(defun C:3DSPIRAL (/ olderr ocmd oblp nt bp hg vg sr lp) 
  ;;;;(setq olderr  *error*
  ;;;;      *error* myerror)
  (setq ocmd (getvar "cmdecho"))
  (setq oblp (getvar "blipmode"))
  (setvar "cmdecho" 0)
  (initget 1)                         ; bp must not be null
  (setq bp (getpoint "\nMittelpunkt: "))
  (initget 7)                         ; nt must not be zero, neg, or null
  (setq nt (getint "\nAnzahl der Umdrehungen: "))
  (initget 7)                         ; sr must not be zero, neg, or null
  (setq sr (getdist bp "\nStart Radius: "))
  (initget 1)                         ; cf must not be zero, or null
  (setq hg (getdist "\nHoriz Zuwachs pro Umdrehung: "))
  (initget 3)                         ; cf must not be zero, or null
  (setq vg (getdist "\nVert Zuwachs pro Umdrehung: "))
  (initget 6)                         ; lp must not be zero or neg
  (setq lp (getint "\nPunkte pro Umdrehung <30>: "))
  (cond ((null lp) (setq lp 30))) 
  (cspiral nt bp hg lp sr vg)
  (setvar "cmdecho" ocmd)
  (setvar "blipmode" oblp)
  (setq *error* olderr)               ; Restore old *error* handler
  (princ)

) 

;;; --------------------------------------------------------------------------;
(princ "\n\tC:3DSPIRAL loaded. ")
(princ)