#
# Show placement of circles in 3D using
# - sampling
# - circle objects in axis coordinates
# - circle objects and labels in polar (cylindrical) coordinates
#
save_encoding = GPVAL_ENCODING
set encoding utf8

unset border
unset key
set angles degrees
set view 64, 302, 1.62, 1.0
set view azimuth 23.4
set view  equal xyz
set style data lines
set xzeroaxis
set yzeroaxis
set zzeroaxis
set xyplane at 0
unset tics
set xrange [ -1.1  : 1.1  ]
set yrange [ -1.1  : 1.1  ]
set zrange [ -1.1  : 1.1  ]
#
set title "Circle and polygon objects in 3D" font ",20"
set arrow from 0,0,-1.2 to 0,0,1.2 lw 2 filled
#
# Place circles as objects using Cartesian axis coordinates
#
set object 21 circle at 0,0,0  radius 1.0 fs empty border lc "black" lw 3 front
set object 22 circle at 0,0,1  radius 0.1 fs transparent solid 0.5 fc "slategray"
set object 23 circle at 0,0,-1 radius 0.1 fs transparent solid 0.5 fc "slategray"

#
# Pentagonal "base"
#
set obj 24 polygon from polar 0, 0.5, -1.2 to polar 72, 0.5, -1.2 to polar 144, 0.5, -1.2 to polar 216, 0.5, -1.2 to polar 288, 0.5, -1.2 to polar 0, 0.5, -1.2
set obj 24 fillstyle solid border border lc "black" back fc "olive"


#
# Plot symbols for Zodiac constellations in polar (actually cylindrical) coordinates
# Place a circle around the corresponding glyph
# Note: Many fonts do not provide glyphs for these symbols
#
array Zodiac[13] = ["♐", "♑", "♒", "♓", "♈", "♉", "♊", "♋", "♌", "♍", "♎", "♏", "⛎"] 
array Longitude[13] = [267., 300., 328., 352., 29., 53., 90., 118., 138., 174., 218., 241., 248.]
do for [i=1:13] {
    set label i Zodiac[i] at polar Longitude[i], 1.1, 0 center font ",15"
    set obj i circle at polar Longitude[i], 1.1, 0 radius char 1.5
    set obj i fs solid fc rgb hsv2rgb( Longitude[i]/360., 0.5, 1.0)
}

#
# plot sampled parametric circles
#
splot sample [u=0:360] '+' using (cos(u)):(0):(sin(u)) lw 2, \
             [u=0:360] '+' using (cos(u)):(sin(u)):(0) lw 2, \
             [u=0:360] '+' using (0):(cos(u)):(sin(u)) lw 2


Click here for minimal script to generate this plot