face.rb

# frozen_string_literal: true

# https://github.com/sciapp/python-gr/blob/master/examples/face.py

require 'gr'
include Math

x = Array.new(29) { |i| -2 + i * 0.5 }
y = Array.new(29) { |i| -7 + i * 0.5 }
z = []

29.times do |i|
  29.times do |j|
    r1 = sqrt((x[j] - 5)**2 + y[i]**2)
    r2 = sqrt((x[j] + 5)**2 + y[i]**2)
    z[i * 29 + j] = (exp(cos(r1)) + exp(cos(r2)) - 0.9) * 25
  end
end

GR.setcharheight(24.0 / 500)
GR.settextalign(GR::TEXT_HALIGN_CENTER, GR::TEXT_VALIGN_TOP)
GR.textext(0.5, 0.9, 'Surface Example')
tbx, tby = GR.inqtextext(0.5, 0.9, 'Surface Example')
GR.fillarea(tbx, tby)

GR.setwindow(-2, 12, -7, 7)
GR.setspace(-80, 200, 45, 70)

GR.setcharheight(14.0 / 500)
GR.axes3d(1, 0, 20, -2, -7, -80, 2, 0, 2, -0.01)
GR.axes3d(0, 1, 0, 12, -7, -80, 0, 2, 0, 0.01)
GR.titles3d('X-Axis', 'Y-Axis', 'Z-Axis')

GR.surface(x, y, z, 3)
GR.surface(x, y, z, 1)

GR.updatews
gets