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#
# Debugging / test code for Delaunay triangulation, χ-shapes,
# and generation of concave hulls.
#
if (!strstrt(GPVAL_COMPILE_OPTIONS, "+CHI_SHAPES")) {
print "This copy of gnuplot does not support concave hulls"
exit # return to caller
}
set title "Concave hulls" offset 0,-2 font ":Bold"
if (!exists("N")) { N = 17 }
set sample N*10
set print $DATA
do for [i=1:N] {
print rand(0), rand(0)
print rand(0) + 0.3, rand(0) + 0.5
print rand(0) + 0.6, rand(0) - 0.5
print rand(0) + 1.2, rand(0)
}
unset print
set xrange [-.5 : 2.5]
set yrange [-.5 : 2.0]
set isotropic
set key invert
set tics 0.5 nomirror rangelimited
set border 3
plot $DATA using 1:2 convexhull with lines lw 2 lt 4 title "convex", \
$DATA using 1:2 concavehull with lines lc "blue" title "concave", \
$DATA using 1:2 with points pt 7 ps 2 lc bgnd notitle, \
$DATA using 1:2:(sprintf("%d",int($0))) with labels font ",9" notitle, \
keyentry title sprintf("chi_length = %.2f",GPVAL_CHI_LENGTH) noenhanced
pause -1 "<cr> to continue"
set style fill transparent solid 0.25 noborder
plot $DATA using 1:2 concavehull expand .05 smooth path with filledcurve fc "dark-green" \
title "expand .05 smooth concave", \
$DATA using 1:2 concavehull with lines lc "blue" title "concave", \
$DATA using 1:2 convexhull with lines lw 1 lt 4 title "convex", \
$DATA using 1:2 with points pt 7 ps 0.5 lc "black" notitle, \
keyentry title sprintf("chi_length = %.2f",GPVAL_CHI_LENGTH) noenhanced
pause -1 "<cr> to continue"
#
# This uses [undocumented?] filter "delaunay" to convert the original set
# of points into a polygon representation of the Delaunay triangulation.
# This will fail if the debugging code is not present or not enabled.
#
if (N < 50) {
set style fill transparent solid 0.25 border
plot $DATA using 1:2 delaunay with polygons fs empty lw 0.5 title "Delaunay triangulation", \
$DATA using 1:2 concavehull with filledcurve fc "dark-green" lw 2 title "concavehull", \
$DATA using 1:2 with points pt 7 ps 0.5 lc "black" notitle, \
keyentry title sprintf("chi_length = %.2f",GPVAL_CHI_LENGTH) noenhanced
pause -1 "<cr> to continue"
}
reset
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