/*{ "DESCRIPTION":"generated", "CATEGORIES":["generative"], "INPUTS":[
  { "NAME":"speed", "TYPE":"float", "MIN":0.0, "MAX":4.0, "DEFAULT":1.0 },
  { "NAME":"spin", "TYPE":"float", "MIN":0.0, "MAX":2.0, "DEFAULT":1.0 },
  { "NAME":"zoom", "TYPE":"float", "MIN":0.1, "MAX":3.0, "DEFAULT":1.0 },
  { "NAME":"lens", "TYPE":"float", "MIN":0.1, "MAX":1.5, "DEFAULT":0.9 },
  { "NAME":"tube", "TYPE":"float", "MIN":0.01, "MAX":0.3, "DEFAULT":0.08 },
  { "NAME":"hue", "TYPE":"float", "MIN":0.0, "MAX":1.0, "DEFAULT":0.0 },
  { "NAME":"glow", "TYPE":"float", "MIN":0.0, "MAX":3.0, "DEFAULT":1.0 }
]}*/
#define PI  3.14159265359
#define TAU 6.28318530718
#define NV  24

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){
  vec3 p1 = 0.5 + 0.5 * cos(TAU * (t + vec3(0.0, 0.33, 0.66)));
  vec3 p2 = 0.5 + 0.5 * cos(TAU * (t + vec3(0.55, 0.40, 0.18)));
  return mix(p1, p2, 0.5);
}

vec4 vert24(int k){
  int pp = k / 4;
  int ss = k - pp * 4;
  float s0 = mod(float(ss), 2.0) * 2.0 - 1.0;
  float s1 = floor(float(ss) / 2.0) * 2.0 - 1.0;
  if (pp == 0) return vec4(s0, s1, 0.0, 0.0);
  if (pp == 1) return vec4(s0, 0.0, s1, 0.0);
  if (pp == 2) return vec4(s0, 0.0, 0.0, s1);
  if (pp == 3) return vec4(0.0, s0, s1, 0.0);
  if (pp == 4) return vec4(0.0, s0, 0.0, s1);
  return vec4(0.0, 0.0, s0, s1);
}

float segDist(vec3 ro, vec3 rd, vec3 A, vec3 B, out float tray, out float edgeParam){
  vec3 d2 = B - A;
  vec3 r  = ro - A;
  float e = dot(d2, d2);
  float f = dot(d2, r);
  float b = dot(rd, d2);
  float c = dot(rd, r);
  float den = e - b * b;
  float s = (den > 1e-5) ? (b * f - c * e) / den : 0.0;
  s = max(s, 0.0);
  float u = clamp((b * s + f) / e, 0.0, 1.0);
  s = max(dot(A + d2 * u - ro, rd), 0.0);
  tray = s;
  edgeParam = u;
  vec3 pr = ro + rd * s;
  vec3 ps = A + d2 * u;
  return length(pr - ps);
}

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

  float ph = fract(TIME * speed / PERIOD);
  float th = TAU * ph;
  mat2 Rroll = rot(0.4 * spin * sin(th));

  vec4 base[NV];
  vec3 proj[NV];
  float rotw[NV];
  for (int k = 0; k < NV; k++){
    vec4 v = vert24(k);
    base[k] = v;
    v.xz = rot(0.62) * v.xz;
    v.yw = rot(1.13) * v.yw;
    v.xy = rot(th) * v.xy;
    v.zw = rot(th) * v.zw;
    v.xy = Rroll * v.xy;
    rotw[k] = v.w;
    proj[k] = v.xyz / (2.6 - v.w);
  }

  float R = 1.4 * zoom;
  float a  = th;
  float a2 = th + 0.32;
  vec3 ro   = vec3(R * (sin(a)  + 0.35 * sin(3.0 * a)),  0.65 * sin(2.0 * a),
                   R * (cos(a)  + 0.35 * cos(2.0 * a)));
  vec3 look = vec3(R * (sin(a2) + 0.35 * sin(3.0 * a2)), 0.65 * sin(2.0 * a2),
                   R * (cos(a2) + 0.35 * cos(2.0 * a2)));
  vec3 fwd = normalize(mix(normalize(look - ro), normalize(-ro), 0.45));
  vec3 rgt = normalize(cross(vec3(0.0, 1.0, 0.0), fwd));
  vec3 upv = cross(fwd, rgt);

  float rr = length(uv);
  float theta = rr * lens * PI;
  vec2 dir2 = rr > 1.0e-5 ? uv / rr : vec2(0.0, 1.0);
  vec3 rd = normalize(cos(theta) * fwd + sin(theta) * (dir2.x * rgt + dir2.y * upv));

  float w0 = tube * tube;
  vec3 col = vec3(0.0);
  for (int i = 0; i < NV; i++){
    for (int j = 0; j < NV; j++){
      if (j <= i) continue;
      vec4 dv = base[i] - base[j];
      if (abs(dot(dv, dv) - 2.0) > 0.05) continue;
      float tray, edgeParam;
      float d = segDist(ro, rd, proj[i], proj[j], tray, edgeParam);
      float g = w0 / (d * d + w0);
      g = g * g;
      float dots = 0.5 + 0.5 * cos(TAU * edgeParam * 6.0);
      g *= 0.4 + 0.6 * dots;
      float fog = exp(-0.22 * max(tray - 2.0, 0.0));
      float wMid = 0.5 * (rotw[i] + rotw[j]);
      col += pal(hue + wMid * 0.15 + th * 0.02) * g * fog * glow;
    }
  }

  col += vec3(0.02, 0.01, 0.03) * (1.0 - rr * 0.3);

  col = pow(col, vec3(0.7));
  gl_FragColor = vec4(col, 1.0);
}