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# Plot a 3D function
require 'gifplot'
include Math
# Here is the function to plot
def func(x,y)
return 5*cos(2*sqrt(x*x+y*y))*exp(-0.3*sqrt(x*x+y*y))
end
# Here are some plotting parameters
XMIN = -5.0
XMAX = 5.0
YMIN = -5.0
YMAX = 5.0
ZMIN = -5.0
ZMAX = 5.0
# Grid resolution
NXPOINTS = 60
NYPOINTS = 60
cmap = Gifplot::ColorMap.new("cmap")
frame = Gifplot::FrameBuffer.new(500,500)
frame.clear(Gifplot::BLACK)
P3 = Gifplot::Plot3D.new(frame,XMIN,YMIN,ZMIN,XMAX,YMAX,ZMAX)
P3.lookat(2*[XMAX-XMIN,YMAX-YMIN,ZMAX-ZMIN].max)
P3.autoperspective(40)
P3.rotu(60)
P3.rotr(30)
P3.rotd(10)
def drawsolid()
P3.clear(Gifplot::BLACK)
P3.start()
dx = 1.0*(XMAX-XMIN)/NXPOINTS
dy = 1.0*(YMAX-YMIN)/NYPOINTS
cscale = 240.0/(ZMAX-ZMIN)
x = XMIN
for i in 0...NXPOINTS
y = YMIN
for j in 0...NYPOINTS
z1 = func(x,y)
z2 = func(x+dx,y)
z3 = func(x+dx,y+dy)
z4 = func(x,y+dy)
c1 = cscale*(z1-ZMIN)
c2 = cscale*(z2-ZMIN)
c3 = cscale*(z3-ZMIN)
c4 = cscale*(z4-ZMIN)
c = (c1+c2+c3+c4)/4
c = 0 if (c < 0)
c = 239 if c > 239
P3.solidquad(x,y,z1,x+dx,y,z2,x+dx,y+dy,z3,x,y+dy,z4,c+16)
y = y + dy
end
x = x + dx
end
end
puts "Making a nice 3D plot..."
drawsolid()
frame.writeGIF(cmap,"image.gif")
puts "Wrote image.gif"
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