#version 430
layout(local_size_x = 1, local_size_y = 1) in;

uniform float seconds = 0;
layout(rgba8) uniform readonly image2D noise_texture;
layout(rgba8) uniform writeonly image2D output_image;

float sample_noise(in vec2 p) {
  vec4 noise = imageLoad(noise_texture, ivec2(p * imageSize(noise_texture)));
  return noise.x;
}

float gen_pattern(in vec2 p, out vec3 coloring_factor, out vec3 coloring_factor2) {
  float s1 = sample_noise(p + sample_noise(p) * vec2(0.5, 0.1));
  float s2 = sample_noise(p + sample_noise(p) * vec2(0.8, 0.4));
  float s3 = sample_noise(p + sample_noise(p));
  coloring_factor = vec3(s1, s2, 0.8);
  coloring_factor2 = vec3(s2, 0.2, s3);
  return sample_noise(p + s2 * s1 * s3);
}

void main() {
  vec2 resolution = vec2(imageSize(output_image).xy);
  float aspect_ratio = resolution.y / resolution.x;
  vec2 uv = gl_GlobalInvocationID.xy * vec2(1.0, aspect_ratio) / resolution;

  vec3 coloring_factor;
  vec3 coloring_factor2;
  float v = gen_pattern(uv, coloring_factor, coloring_factor2);
  vec3 color = mix(coloring_factor, coloring_factor2, v);

  imageStore(output_image, ivec2(gl_GlobalInvocationID.xy), vec4(color, 1));
}