Adaptive shadow map sampling

SampleShadow.glsl

  uint pixel_index = uint(gl_FragCoord.x) + uint(gl_FragCoord.y) * 4096u;
  uint seed = pcg_hash(pixel_index);
  float shadow = Shadow(seed, fragWorldPos, normal, -shadingUniforms.sunDir.xyz);
  float shadow_accum = shadow;
  int succ = 0;
  for (int i = 0; i < 4; i++)
  {
    if (shadow_accum / (i + 1) > 0.0 && shadow_accum / (i + 1) < 2.0 / (shadowUniforms.pcfSamples * (i + 1)) + 0.0001)
    {
      succ++;
      seed = pcg_hash(seed ^ 12321);
      shadow = Shadow(seed, fragWorldPos, normal, -shadingUniforms.sunDir.xyz);
      shadow_accum += shadow;
      // switch (i)
      // {
      // case 0: diffuse = vec3(1, 0, 0); break;
      // case 1: diffuse = vec3(0, 1, 0); break;
      // case 2: diffuse = vec3(0, 1, 1); break;
      // case 3: diffuse = vec3(1, 1, 0); break;
      // }
    }
  }
  shadow = shadow_accum / (succ + 1);