/*{
  "DESCRIPTION": "A camera trapped inside a rotating geode cavity. Its overlapping spiral chambers are dark mineral, while a living Chladni fracture field crawls across the concave walls and opens onto an iridescent void.",
  "CREDIT": "glslop",
  "CATEGORIES": ["Raymarch", "3D", "Generative"],
  "INPUTS": [
    { "NAME": "blend", "TYPE": "float", "DEFAULT": 0.2, "MIN": 0.08, "MAX": 0.45 },
    { "NAME": "spinTurns", "TYPE": "float", "DEFAULT": 1.0, "MIN": 0.0, "MAX": 3.0 },
    { "NAME": "lookTurns", "TYPE": "float", "DEFAULT": 2.0, "MIN": 1.0, "MAX": 4.0 },
    { "NAME": "fracture", "TYPE": "float", "DEFAULT": 0.72, "MIN": 0.2, "MAX": 1.0 },
    { "NAME": "voidHue", "TYPE": "color", "DEFAULT": [0.08, 0.02, 0.14, 1.0] }
  ]
}*/

#define STEPS 110
#define GEMS 7
#define PI 3.14159265359
#define PERIOD 8.0
#define OUTER_R 1.9

vec3 rotY(vec3 p, float a){
  float c = cos(a), s = sin(a);
  return vec3(c*p.x + s*p.z, p.y, -s*p.x + c*p.z);
}

float smin(float a, float b, float k){
  float h = clamp(0.5 + 0.5*(b - a)/k, 0.0, 1.0);
  return mix(b, a, h) - k*h*(1.0 - h);
}

float sdSphere(vec3 p, vec3 c, float r){
  return length(p - c) - r;
}

float cavityField(vec3 p, float spinAngle){
  vec3 pr = rotY(p, -spinAngle);
  float d = sdSphere(pr, vec3(0.0), 0.5);
  for (int i = 0; i < GEMS; i++){
    float a = (float(i) / float(GEMS)) * 2.0 * PI;
    float rise = 0.22 * sin(a * 2.0);
    vec3 c = vec3(cos(a) * 0.85, rise, sin(a) * 0.85);
    float r = 0.46 + 0.04 * cos(a * 3.0);
    d = smin(d, sdSphere(pr, c, r), blend);
  }
  return d;
}

float map(vec3 p, float spinAngle){
  float outer = length(p) - OUTER_R;
  return max(outer, -cavityField(p, spinAngle));
}

vec3 normalAt(vec3 p, float spinAngle){
  vec2 e = vec2(0.002, 0.0);
  return normalize(vec3(
    map(p + e.xyy, spinAngle) - map(p - e.xyy, spinAngle),
    map(p + e.yxy, spinAngle) - map(p - e.yxy, spinAngle),
    map(p + e.yyx, spinAngle) - map(p - e.yyx, spinAngle)
  ));
}

vec3 filmColor(float ph){
  return 0.5 + 0.5 * cos(2.0 * PI * (fract(ph) + vec3(0.0, 0.33, 0.67)));
}

float rockGrain(vec3 p){
  float a = sin(dot(p, vec3(7.1, 11.7, 5.3)));
  float b = sin(dot(p, vec3(-4.3, 8.9, 13.1)));
  return 0.5 + 0.5 * sin(5.0 * a + 3.0 * b + p.y * 9.0);
}

float mode(vec2 p, float m, float n){
  return sin(PI * m * p.x) * sin(PI * n * p.y)
       - sin(PI * n * p.x) * sin(PI * m * p.y);
}

float fractureField(vec3 p, float spinAngle, float ph){
  // Project two Chladni mode families through the local cavity coordinates so
  // the fracture network wraps around the rotating wall instead of sitting in
  // screen space like a flat overlay.
  vec3 q = rotY(p, -spinAngle * 0.6);
  vec2 a = q.xy * 1.25 + 0.035 * vec2(sin(q.y * 7.0 + ph * 6.28), cos(q.x * 6.0 - ph * 6.28));
  vec2 b = vec2(q.z, q.y) * 1.35;
  float w = 0.5 + 0.5 * cos(2.0 * PI * ph);
  float f1 = mode(a, 3.0, 7.0);
  float f2 = mode(b, 5.0, 4.0);
  return mix(f1, f2, w);
}

void main(){
  vec2 uv = (gl_FragCoord.xy - 0.5 * RENDERSIZE.xy) / RENDERSIZE.y;
  float ph = fract(TIME / PERIOD);
  float spinAngle = 2.0 * PI * ph * spinTurns;
  float lookAngle = 0.5 * PI + 0.6 * sin(2.0 * PI * ph * lookTurns);

  vec3 ro = vec3(0.0, 0.0, 0.0);
  vec3 fwd = rotY(vec3(0.0, 0.0, 1.0), lookAngle);
  vec3 right = normalize(cross(fwd, vec3(0.0, 1.0, 0.0)));
  vec3 up = cross(right, fwd);
  vec3 rd = normalize(fwd * 1.55 + uv.x * right + uv.y * up);

  float t = 0.02;
  float hit = -1.0;
  float glowAcc = 0.0;
  for (int i = 0; i < STEPS; i++){
    vec3 p = ro + rd * t;
    float d = map(p, spinAngle);
    glowAcc += 0.01 / (1.0 + 90.0 * d * d);
    if (d < 0.001){
      hit = t;
      break;
    }
    t += d;
    if (t > 7.0) break;
  }

  vec3 col = vec3(0.008, 0.006, 0.018) + glowAcc * filmColor(ph * 2.0 + 0.4) * 0.8;

  if (hit > 0.0){
    vec3 p = ro + rd * hit;
    vec3 n = normalAt(p, spinAngle);
    float vDotN = clamp(dot(-rd, n), 0.0, 1.0);

    float grain = rockGrain(p * 2.2);
    float strata = 0.5 + 0.5 * cos(p.y * 18.0 + sin(p.x * 5.0 + p.z * 4.0));
    float filmPhase = vDotN * 2.8 + p.y * 1.8 + grain * 0.28 + ph + 0.5;
    vec3 film = filmColor(filmPhase);
    vec3 mineral = mix(vec3(0.010, 0.007, 0.024), vec3(0.065, 0.016, 0.085), grain);
    mineral *= 0.65 + 0.35 * strata;

    vec3 keyDir = normalize(vec3(-0.5, 0.8, 0.35));
    vec3 fillDir = normalize(vec3(0.65, -0.25, -0.7));
    float key = max(dot(n, keyDir), 0.0);
    float fill = max(dot(n, fillDir), 0.0);
    float fres = pow(1.0 - vDotN, 3.0);
    float glint = pow(max(dot(reflect(rd, n), keyDir), 0.0), 18.0);
    float depth = exp(-0.24 * hit);

    vec3 shaded = mineral * (0.10 + 1.75 * key + 0.48 * fill) * depth;
    shaded += film * (0.035 + 0.22 * key + 0.10 * fres);
    shaded += fres * vec3(0.16, 0.46, 0.60) + glint * vec3(0.85, 0.56, 0.22);

    float A = fractureField(p, spinAngle, ph);
    float node = 1.0 - smoothstep(0.0, 0.06, abs(A));
    float branchField = A + 0.10 * sin(p.x * 17.0 + p.y * 9.0 + ph * 6.28318);
    float branches = 1.0 - smoothstep(0.0, 0.035, abs(branchField));
    float scar = max(node, branches * 0.48) * mix(0.55, 1.0, fracture);
    float crack = smoothstep(0.10, 0.48, scar);
    float hairline = smoothstep(0.015, 0.18, scar);
    float crackEdge = clamp(hairline - crack, 0.0, 1.0);

    vec3 voidCol = voidHue.rgb * (0.35 + 0.65 * filmColor(ph * 0.7 + p.x * 0.22 - p.y * 0.31 + scar * 0.8));
    shaded = mix(shaded, voidCol * 0.22, crack * 0.82);
    shaded += filmColor(ph * 0.7 + p.x * 0.22 - p.y * 0.31) * crackEdge * 0.9;

    float fog = exp(-0.16 * hit);
    col = mix(col, shaded, fog);
  }

  col = col / (1.0 + col);
  col = pow(max(col, 0.0), vec3(0.4545));
  gl_FragColor = vec4(col, 1.0);
}