#
# Demonstrate construction and use of a separate palette
# Ethan A Merritt - May 2020
#
# Method 1:
# The first method works in 5.2 but requires "lc rgb variable"
# rather than the more natural "fillcolor rgb variable".
# "set pm3d interpolate" breaks the color mapping of this method
#
# This creates a palette equivalent to
# set palette defined (0 "dark-blue", 1 "white")
#
array blues[256]
do for [i=1:256] {
blues[i] = int( (0x7f + (i-1)/(255.) * 0xffff80) );
}
#
# This is the equivalent of
# set cbrange [-1:1]
blues_min = -1
blues_max = 1
#
# This function maps z onto a palette color
#
blues(z) = (z <= blues_min) ? blues[1] \
: (z >= blues_max) ? blues[256] \
: blues[ floor(255. * (z-blues_min)/(blues_max-blues_min)) + 1]
foo(x,y) = sin(x*y)
set samples 41
set isosamples 41
unset colorbox
set cbrange [-1:1]
set xrange [0:5]
set yrange [0:5]
set title "Use hand-constructed 'blues' palette via rgb variable"
splot '++' using 1:2:(foo($1,$2)):(blues(foo($1,$2))) with pm3d lc rgb variable \
title "pm3d using 1:2:3:4 with pm3d lc rgb variable"
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#
# Method 2 (new in version 6)
# "set pm3d interpolate" works now
# "set pm3d lighting" also works
set title "Version 6 offers a new keyword to access this palette"
set palette defined (0 "dark-blue", 1 "white")
set colormap new bluemap
splot '++' using 1:2:(foo($1,$2)) with pm3d fc palette bluemap\
title "pm3d using 1:2:3 with pm3d fc palette bluemap"
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set title "Named colormaps allow pm3d interpolation and lighting" set pm3d interpolate 2,2 set pm3d lighting replot |
#
# Demonstrate use of multiple palettes in the same plot
#
set title "pm3d coloring using two named colormap palettes"
set palette defined (0 "turquoise", 1 "dark-green")
set colormap new water
set palette defined (0 "yellow", 1 "red") negative
set colormap new flame
set pm3d implicit
set pm3d depthorder
set pm3d lighting
set auto
unset border
unset key
set object 1 rect from screen 0, 0, 0 to screen 1, 1, 0 behind
set object 1 rect fc rgb "gray" fillstyle solid 1.0 border -1
set view equal xyz
set view 290, 11, 2.2, 1.2
set isosamples 100, 40
unset tics
set parametric
set dummy u,v
set urange [ -pi : pi ]
set vrange [ -pi : pi ]
# construct colorboxes for the two named palettes
set pixmap 1 colormap water at screen 0.92, 0.3 size screen 0.03, 0.4 back
set pixmap 2 colormap flame at screen 0.2, 0.04 size screen 0.4, 0.03 back
set obj 11 rect from screen 0.92, 0.3 rto screen 0.03, 0.4 fs empty back
set obj 12 rect from screen 0.2, 0.04 rto screen 0.4, 0.03 fs empty back
splot cos(u)+.5*cos(u)*cos(v),sin(u)+.5*sin(u)*cos(v),.5*sin(v) fc palette flame, \
1+cos(u)+.5*cos(u)*cos(v),.5*sin(v),sin(u)+.5*sin(u)*cos(v) fc palette water
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reset |