precision mediump float;

uniform vec2 u_resolution;
uniform float u_time;
uniform vec2 u_mouse;

varying vec2 vUv;

const float PI = 3.1415926;
const float TAU = 6.2831853;

uvec3 k = uvec3(0x456789abu, 0x6789ab45u, 0x89ab4567u);
uvec3 u = uvec3(1, 2, 3);
const uint UINT_MAX = 0xffffffffu;

uint uhash11(uint n){
  n ^= (n << u.x);
  n ^= (n >> u.x);
  n *= k.x;
  n ^= (n << u.x);
  return n * k.x;
}

uvec2 uhash22(uvec2 n){
  n ^= (n.yx << u.xy);
  n ^= (n.yx >> u.xy);
  n *= k.xy;
  n ^= (n.yx << u.xy);
  return n * k.xy;
}

uvec3 uhash33(uvec3 n){
  n ^= (n.yzx << u);
  n ^= (n.yzx >> u);
  n *= k;
  n ^= (n.yzx << u);
  return n * k;
}

float hash11(float p){
  uint n = floatBitsToUint(p);
  return float(uhash11(n)) / float(UINT_MAX);
}

float hash21(vec2 p){
  uvec2 n = floatBitsToUint(p);
  return float(uhash22(n).x) / float(UINT_MAX);
}

float hash31(vec3 p){
  uvec3 n = floatBitsToUint(p);
  return float(uhash33(n).x) / float(UINT_MAX);
}

vec2 hash22(vec2 p){
  uvec2 n = floatBitsToUint(p);
  return vec2(uhash22(n)) / vec2(UINT_MAX);
}

vec3 hash33(vec3 p){
  uvec3 n = floatBitsToUint(p);
  return vec3(uhash33(n)) / vec3(UINT_MAX);
}

vec2 rot2(vec2 p, float t) {
  return vec2(cos(t) * p.x - sin(t) * p.y, sin(t) * p.x + cos(t) * p.y);
}

vec3 rotX(vec3 p, float t) {
  return vec3(p.x, rot2(p.yz, t));
}

vec3 rotY(vec3 p, float t) {
  return vec3(p.y, rot2(p.zx, t)).zxy;
}

vec3 rotZ(vec3 p, float t) {
  return vec3(rot2(p.xy, t), p.z);
}

vec3 euler(vec3 p, vec3 t){
  return rotZ(rotY(rotX(p, t.x), t.y), t.z);
}

//start pnoise
float gtable2(vec2 lattice, vec2 p){
  uvec2 n = floatBitsToUint(lattice);
  uint ind = uhash22(n).x >> 29;
  float u = 0.92387953 * (ind < 4u ? p.x : p.y);  //0.92387953 = cos(pi/8)
  float v = 0.38268343 * (ind < 4u ? p.y : p.x);  //0.38268343 = sin(pi/8)
  return ((ind & 1u) == 0u ? u : -u) + ((ind & 2u) == 0u? v : -v);
}

float pnoise21(vec2 p){
  vec2 n = floor(p);
  vec2 f = fract(p);
  float[4] v;
  for (int j = 0; j < 2; j ++){
    for (int i = 0; i < 2; i++){
      v[i+2*j] = gtable2(n + vec2(i, j), f - vec2(i, j));
    }
  }
  f = f * f * f * (10.0 - 15.0 * f + 6.0 * f * f);
  return 0.5 * mix(mix(v[0], v[1], f[0]), mix(v[2], v[3], f[0]), f[1]) + 0.5;
}

float gtable3(vec3 lattice, vec3 p){
  uvec3 n = floatBitsToUint(lattice);
  uint ind = uhash33(n).x >> 28;
  float u = ind < 8u ? p.x : p.y;
  float v = ind < 4u ? p.y : ind == 12u || ind == 14u ? p.x : p.z;
  return ((ind & 1u) == 0u? u: -u) + ((ind & 2u) == 0u? v : -v);
}

float pnoise31(vec3 p){
  vec3 n = floor(p);
  vec3 f = fract(p);
  float[8] v;
  for (int k = 0; k < 2; k++ ){
    for (int j = 0; j < 2; j++ ){
      for (int i = 0; i < 2; i++){
        v[i+2*j+4*k] = gtable3(n + vec3(i, j, k), f - vec3(i, j, k)) * 0.70710678;
      }
    }
  }
  f = f * f * f * (10.0 - 15.0 * f + 6.0 * f * f);
  float[2] w;
  for (int i = 0; i < 2; i++){
    w[i] = mix(mix(v[4*i], v[4*i+1], f[0]), mix(v[4*i+2], v[4*i+3], f[0]), f[1]);
  }
  return 0.5 * mix(w[0], w[1], f[2]) + 0.5;
}
//end pnoise

float sphereSDF(vec3 p) {
  return length(p) - 1.0;
}

float sceneSDF(vec3 p) {
  return sphereSDF(p);
}

vec3 gradSDF(vec3 p) {
  float eps = 0.001;
  return normalize(vec3(
    sceneSDF(p + vec3(eps, 0.0, 0.0)) - sceneSDF(p - vec3(eps, 0.0, 0.0)),
    sceneSDF(p + vec3(0.0, eps, 0.0)) - sceneSDF(p - vec3(0.0, eps, 0.0)),
    sceneSDF(p + vec3(0.0, 0.0, eps)) - sceneSDF(p - vec3(0.0, 0.0, eps))
  ));
}

void main() {
  vec2 pos = (2.0 * gl_FragCoord.xy - u_resolution.xy) / min(u_resolution.x, u_resolution.y);

  float t = u_time * 0.3;

  vec3 cPos = rotY(vec3(0.0, 0.0, 2.0), t);
  vec3 cDir = rotY(vec3(0.0, 0.0, -1.0), t);
  vec3 cUp = rotY(vec3(0.0, 1.0, 0.0), t);
  vec3 cSide = cross(cDir, cUp);

  float targetDepth = 1.0;
  vec3 lDir = rotY(vec3(1.0), t);

  vec3 ray = cSide * pos.x + cUp * pos.y + cDir * targetDepth;
  vec3 rPos = ray + cPos;
  ray = normalize(ray);

  gl_FragColor.rgb = vec3(0.0);

  for (int i = 0; i < 50; i++) {
    if (sceneSDF(rPos) > 0.001) {
      rPos += sceneSDF(rPos) * ray;
    } else {
      float amb = 0.1;
      float diff = 0.9 * max(dot(normalize(lDir), gradSDF(rPos)), 0.0);
      float text = pnoise31(10.0 * rPos);
      gl_FragColor.rgb = (diff + amb) * vec3(text);
      break;
    }
  }

  gl_FragColor.a = 1.0;
}