/*{
  "DESCRIPTION": "Nacre Bulb: the power-8 Mandelbulb raymarched as a slowly turning alien artifact carved from opal — bulbous lobes and deep folds sheathed in oil-slick thin-film iridescence that shifts pink, green and gold across the fractal detail. Rotates once for a seamless 16s loop. Real-time.",
  "CREDIT": "glslop agent (Claude)",
  "CATEGORIES": ["mandelbulb", "fractal", "3d", "raymarch", "neon"],
  "INPUTS": [
    { "NAME": "speed",  "TYPE": "float", "DEFAULT": 1.0,  "MIN": 0.0, "MAX": 3.0 },
    { "NAME": "glow",   "TYPE": "float", "DEFAULT": 1.0,  "MIN": 0.3, "MAX": 3.0 },
    { "NAME": "hue",    "TYPE": "float", "DEFAULT": 0.0,  "MIN": 0.0, "MAX": 1.0 },
    { "NAME": "power",  "TYPE": "float", "DEFAULT": 8.0,  "MIN": 3.0, "MAX": 10.0 },
    { "NAME": "zoom",   "TYPE": "float", "DEFAULT": 1.0,  "MIN": 0.6, "MAX": 1.8 }
  ]
}*/

#define PI  3.14159265359
#define TAU 6.28318530718
#define ITER 8

const float PERIOD = 16.0;

mat2 rot(float a){ float c = cos(a), s = sin(a); return mat2(c, -s, s, c); }
vec3 pal(float t){ return 0.5 + 0.5 * cos(TAU * (t + vec3(0.0, 0.33, 0.66))); }

float gTrap;

float de(vec3 p){
  vec3 z = p;
  float dr = 1.0;
  float r = 0.0;
  float trap = 1e9;
  for (int i = 0; i < ITER; i++){
    r = length(z);
    if (r > 2.0) break;
    float theta = acos(clamp(z.z / r, -1.0, 1.0));
    float phi = atan(z.y, z.x);
    float zr = pow(r, power);
    dr = pow(r, power - 1.0) * power * dr + 1.0;
    theta *= power;
    phi *= power;
    z = zr * vec3(sin(theta) * cos(phi), sin(theta) * sin(phi), cos(theta)) + p;
    trap = min(trap, dot(z, z));
  }
  gTrap = trap;
  return 0.5 * log(r) * r / dr;
}

vec3 calcNormal(vec3 p){
  vec2 e = vec2(1.0, -1.0) * 0.0008;
  return normalize(e.xyy * de(p + e.xyy) + e.yyx * de(p + e.yyx)
                 + e.yxy * de(p + e.yxy) + e.xxx * de(p + e.xxx));
}

void main(){
  vec2 uv = (gl_FragCoord.xy - 0.5 * RENDERSIZE.xy) / RENDERSIZE.y;

  float ph = fract(TIME * speed / PERIOD);
  float th = TAU * ph;

  vec3 ro = vec3(0.0, 0.0, 3.4 / zoom);
  vec3 ww = normalize(-ro);
  vec3 uu = normalize(cross(vec3(0.0, 1.0, 0.0), ww));
  vec3 vv = cross(ww, uu);
  vec3 rd = normalize(uv.x * uu + uv.y * vv + 1.3 * ww);

  // rotate the ray into the bulb's frame -> bulb turns one full revolution (seamless)
  mat2 ry = rot(th);
  mat2 rx = rot(0.5 + 0.25 * sin(th));
  ro.xz = ry * ro.xz; rd.xz = ry * rd.xz;
  ro.yz = rx * ro.yz; rd.yz = rx * rd.yz;

  float t = 0.0;
  float trap = 1e9;
  bool hit = false;
  for (int i = 0; i < 130; i++){
    vec3 p = ro + rd * t;
    float d = de(p);
    if (d < 0.0004 * t){ hit = true; trap = gTrap; break; }
    t += d * 0.85;
    if (t > 6.0) break;
  }

  vec3 col = vec3(0.0);
  if (hit){
    vec3 p = ro + rd * t;
    vec3 n = calcNormal(p);
    vec3 lig = normalize(vec3(0.7, 0.8, 0.4));
    float dif = clamp(dot(n, lig), 0.0, 1.0);
    float fres = pow(1.0 - clamp(dot(n, -rd), 0.0, 1.0), 4.0);
    float ao = 1.0 / (1.0 + t * 0.3);

    float tr = sqrt(trap);
    // molten metal: deep copper in the folds -> bright gold on the lobes
    vec3 metal = mix(vec3(0.70, 0.26, 0.07), vec3(1.0, 0.82, 0.42), smoothstep(0.0, 0.55, tr));
    vec3 accent = mix(vec3(0.2, 0.75, 1.0), pal(hue + 0.55), hue);   // cyan recess glow (hue retints)

    col  = metal * (0.30 + 1.1 * dif) * ao;                // lit molten body
    col += vec3(0.22, 0.10, 0.06) * ao;                    // warm ambient (not grey)
    col += accent * smoothstep(1.1, 0.0, tr) * 2.2 * glow; // glowing recesses (wider, brighter)
    // thin-film iridescence sheen -> oil-on-bronze colour shimmer
    vec3 irid = pal(hue + ph + 1.6 * fres + 0.35 * n.y + 0.2 * tr);
    col = mix(col, col * irid * 1.8 + irid * 0.25, 0.5);
    col += mix(metal, vec3(1.0), 0.6) * fres * 2.2 * glow; // hot rim
    col += vec3(1.0, 0.95, 0.85) * pow(dif, 14.0) * 1.1;   // sharp specular
    col *= exp(-0.1 * max(t - 2.4, 0.0));                  // depth fog
  } else {
    // subtle backdrop glow so it doesn't float in flat black
    col = pal(hue + 0.6) * 0.03 * (1.0 - length(uv) * 0.6);
  }

  col = col / (1.0 + col);
  col = pow(col, vec3(0.85));
  col *= 1.0 - 0.16 * dot(uv, uv);
  gl_FragColor = vec4(col, 1.0);
}