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############################################################################
#
# File: orbits.icn
#
# Subject: Procedures to produce traces of orbits
#
# Author: Ralph E. Griswold
#
# Date: May 2, 2001
#
############################################################################
#
# This file is in the public domain.
#
############################################################################
#
# These procedures produce traces of orbits. See
#
# Geometric and Artistic Graphics; Design Generation with
# Microcomputers, Jean-Paul Delahaye, Macmillan, 1987, pp. 65-73.
#
# The arguments specify the starting positions, the extent of the
# drawing, the number of segments, and various parameters that
# control the orbit.
#
############################################################################
#
# Links: gobject
#
############################################################################
link gobject
procedure orbit1(x, y, extent, n, t1, t2, k1, k2, radius1, sscale,
xfact, yfact)
local incr1, incr2, real_n, angle1, angle2, i, radius2, loff
radius1 *:= extent #scaling
loff := 0.5 * extent
sscale *:= extent
real_n := real(n)
incr1 := 2 * &pi * t1 / n
incr2 := 2 * &pi * t2 / n
angle1 := angle2 := 0
every i := 1 to n do {
radius2 := sscale * (1 - i / real_n)
angle1 +:= incr1
angle2 +:= incr2
suspend Point(x + xfact * (loff + radius1 * cos(k1 * angle1) +
radius2 * cos(angle2)),
y + yfact * (loff + radius1 * sin(k2 * angle1) +
radius2 * sin(angle2)))
}
end
procedure orbit2(x, y, extent, n, t1, t2, k1, k2, radius1, sscale,
xfact, yfact, roff, rfact, rratio, div)
local incr1, incr2, rangle, angle1, angle2, i, radius2, loff
rangle := 2 * &pi / div * rratio
radius1 *:= extent #scaling
loff := 0.5 * extent
sscale *:= extent
incr1 := 2 * &pi * t1 / n
incr2 := 2 * &pi * t2 / n
angle1 := angle2 := 0
every i := 1 to n do {
radius2 := sscale * (roff + rfact * cos(i * rangle))
angle1 +:= incr1
angle2 +:= incr2
suspend Point(x + xfact * (loff + radius1 * cos(k1 * angle1) +
radius2 * cos(angle2)),
y + yfact * (loff + radius1 * sin(k2 * angle1) +
radius2 * sin(angle2)))
}
end
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