I found this thinking that someday I would need it. So now I share it with you in case you too need it. After all without it, how else can you easily make a spiral in AutoCAD?
This routine is from 1985 and shows that old AutoLISP routines still work after a 26 years.
Here’s how it works:
- SPIRAL <enter> to start
- Specify center point of the spiral
- Specify # of rotations
- Specify the spacing between the rotations
- Specify how many polyline segments in each rotation (the more segments, the rounder the polyline will appear)
; This is a programming example. ; ; 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" or the following: ; (cspiral <# rotations> <base point> <growth per rotation> ; <points per circle>). ; (defun cspiral (ntimes bpoint cfac lppass / ang dist tp ainc dinc circle bs cs) (setq cs (getvar "cmdecho")) ; save old cmdecho and blipmode (setq bs (getvar "blipmode")) (setvar "blipmode" 0) ; turn blipmode off (setvar "cmdecho" 0) ; turn cmdecho off (setq circle (* 3.141596235 2)) (setq ainc (/ circle lppass)) (setq dinc (/ cfac lppass)) (setq ang 0.0) (setq dist 0.0) (command "pline" bpoint) ; start spiral from base point and... (repeat ntimes (repeat lppass (setq tp (polar bpoint (setq ang (+ ang ainc)) (setq dist (+ dist dinc)))) (command tp) ; continue to the next point... ) ) (command) ; until done. (setvar "blipmode" bs) ; restore saved blipmode (setvar "cmdecho" cs) ; restore saved cmdecho nil ) ; ; Interactive spiral generation ; (defun C:SPIRAL ( / nt bp cf lp) (initget 1) ; bp must not be null (setq bp (getpoint "\nCenter point: ")) (initget 7) ; nt must not be zero, neg, or null (setq nt (getint "\nNumber of rotations: ")) (initget 3) ; cf must not be zero, or null (setq cf (getdist "\nGrowth per rotation: ")) (initget 6) ; lp must not be zero or neg (setq lp (getint "\nPoints per rotation <30>: ")) (cond ((null lp) (setq lp 30))) (cspiral nt bp cf lp) )