00001
00002 c
00003 c Copyright (c) 1986,1987,1988,1989,1990,1991,1992,1993,
00004 c by Steve McMillan, Drexel University, Philadelphia, PA.
00005 c
00006 c All rights reserved.
00007 c
00008 c Redistribution and use in source and binary forms are permitted
00009 c provided that the above copyright notice and this paragraph are
00010 c duplicated in all such forms and that any documentation,
00011 c advertising materials, and other materials related to such
00012 c distribution and use acknowledge that the software was developed
00013 c by the author named above.
00014 c
00015 c THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
00016 c IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
00017 c WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
00018 c
00019 c
00020 c
00021 c--- subroutine: spiral
00022 c
00023 c--- draws logarithmic spirals
00024 c r radius of spiral in inches
00025 c a number of spirals per inch
00026 c t angle of starting curve (degrees cc from x-axis)
00027 c i direction of spiral (+1 = ccl, -1 = cl)
00028 c x,y location of center
00029 c
00030 subroutine spiral (r,a,t,i,x,y)
00031 save
00032 pi=3.1415926
00033 c
00034 c1=.02*pi
00035 c2=2.*pi*a
00036 c3=2.*pi*t/360.
00037 call plot(x,y,3)
00038 c
00039 do 10 j=1,100*a*r
00040 th=c1*j
00041 ra=th/c2
00042 th=c3+i*th
00043 x1=x+ra*cos(th)
00044 y1=y+ra*sin(th)
00045 call plot(x1,y1,2)
00046 10 continue
00047 end
