mandelbrot_glsl.rb

require 'ray'

ImageWidth  = 640
ImageHeight = 480

image = Ray::Image.new [ImageWidth, ImageHeight]

Ray::ImageTarget.new image do |target|
  target.shader.compile(:frag => StringIO.new(<<eof))
#version 130

uniform sampler2D in_Texture;

const int max_it = 50;
const float width  = #{ImageWidth.to_f};
const float height = #{ImageHeight.to_f};

in  vec4 var_Color;
out vec4 out_FragColor;

vec2 mandelbrot_pos() {
 return vec2(((gl_FragCoord.x) / width) * 2.7 - 2.1,
             ((gl_FragCoord.y) / height) * 2.4 - 1.2);
}

vec2 complex_square(vec2 complex) {
  return vec2(complex.x * complex.x - complex.y * complex.y,
              complex.x * complex.y + complex.x * complex.y);
}

vec4 inverse(vec4 color) {
  return vec4(vec3(1,1,1) - color.rgb, 1.0);
}

void main() {
  vec2 c = mandelbrot_pos();
  vec2 z = vec2(0, 0);

  int i = 0;

  for (i = 0; i < max_it; i++) {
    z = complex_square(z) + c;
    if (dot(z, z) > 4.0) break;
  }

  out_FragColor = i == max_it ? var_Color : inverse(var_Color);
}
eof

  target.draw Ray::Polygon.rectangle([0, 0, ImageWidth, ImageHeight],
                                     Ray::Color.black)
  target.update
end

Ray.game "Mandelbrot", :size => image.size do
  register { add_hook :quit, method(:exit!) }

  scene :mandelbrot do
    @sprite = sprite(image)

    render do |win|
      win.draw @sprite
    end
  end

  scenes << :mandelbrot
end