/*{
  "DESCRIPTION": "Soft rising smoke advected through a looping curl-like flow field.",
  "INPUTS": [
    { "NAME": "flowSpeed", "TYPE": "float", "DEFAULT": 1.0, "MIN": 0.0, "MAX": 2.5 },
    { "NAME": "turbulence", "TYPE": "float", "DEFAULT": 1.0, "MIN": 0.0, "MAX": 2.0 },
    { "NAME": "dissipation", "TYPE": "float", "DEFAULT": 0.985, "MIN": 0.94, "MAX": 0.999 },
    { "NAME": "emitterSize", "TYPE": "float", "DEFAULT": 0.055, "MIN": 0.015, "MAX": 0.14 },
    { "NAME": "smokeColor", "TYPE": "color", "DEFAULT": [0.36, 0.62, 1.0, 1.0] }
  ],
  "PASSES": [
    { "TARGET": "smokeBuffer", "PERSISTENT": true, "FLOAT": true },
    {}
  ]
}*/

#define TAU 6.28318530718

vec2 velocityField(vec2 uv, float t) {
  vec2 p = uv;
  p.x += 0.07 * sin(t * 0.37);
  p.y += 0.05 * cos(t * 0.29);

  float sx = sin(TAU * p.x);
  float cx = cos(TAU * p.x);
  float sy = sin(TAU * p.y);
  float cy = cos(TAU * p.y);

  vec2 v = vec2(sx * cy, -cx * sy);
  v += 0.42 * vec2(
    sin(TAU * (2.0 * p.y + 0.17 * t)),
    cos(TAU * (2.0 * p.x - 0.13 * t))
  );
  v += vec2(0.0, 1.35);
  return v;
}

void main() {
  vec2 uv = isf_FragNormCoord;

  if (PASSINDEX == 0) {
    float frameStep = min(TIMEDELTA * 60.0, 2.0);
    vec2 vel = velocityField(uv, TIME * flowSpeed) * turbulence;
    vec2 back = uv - vel * (0.0018 * frameStep * flowSpeed);
    vec2 px = 1.0 / RENDERSIZE;

    float density = IMG_NORM_PIXEL(smokeBuffer, back).r * 0.52;
    density += IMG_NORM_PIXEL(smokeBuffer, back + vec2(2.0 * px.x, 0.0)).r * 0.12;
    density += IMG_NORM_PIXEL(smokeBuffer, back - vec2(2.0 * px.x, 0.0)).r * 0.12;
    density += IMG_NORM_PIXEL(smokeBuffer, back + vec2(0.0, 2.0 * px.y)).r * 0.12;
    density += IMG_NORM_PIXEL(smokeBuffer, back - vec2(0.0, 2.0 * px.y)).r * 0.12;
    density *= pow(dissipation, frameStep);

    float emitterX = 0.5 + 0.18 * sin(TIME * 0.73) + 0.05 * sin(TIME * 1.91);
    vec2 d = uv - vec2(emitterX, 0.07);
    d.x *= RENDERSIZE.x / RENDERSIZE.y;
    float source = smoothstep(emitterSize, 0.0, length(d));
    vec2 d2 = uv - vec2(emitterX - 0.055, 0.055 + 0.012 * sin(TIME * 2.1));
    d2.x *= RENDERSIZE.x / RENDERSIZE.y;
    source += 0.65 * smoothstep(emitterSize * 0.78, 0.0, length(d2));
    source *= 0.72 + 0.28 * sin(TIME * 5.0 + uv.x * 31.0);
    density += source * 0.19 * frameStep;

    float boundary = smoothstep(0.0, 0.035, uv.x)
                   * smoothstep(0.0, 0.035, 1.0 - uv.x)
                   * smoothstep(0.0, 0.025, uv.y)
                   * smoothstep(0.0, 0.06, 1.0 - uv.y);
    density *= boundary;

    gl_FragColor = vec4(clamp(density, 0.0, 1.5), 0.0, 0.0, 1.0);
  } else {
    float density = IMG_THIS_PIXEL(smokeBuffer).r;
    vec2 p = isf_FragNormCoord * 2.0 - 1.0;
    p.x *= RENDERSIZE.x / RENDERSIZE.y;

    vec3 warm = vec3(0.72, 0.28, 0.12);
    vec3 tint = mix(warm, smokeColor.rgb, 0.72 + 0.20 * sin(density * 5.0));
    vec3 col = tint * (0.35 * sqrt(max(density, 0.0)) + 2.15 * density * density);
    col += vec3(0.05, 0.09, 0.16) * density;
    col *= 1.0 - 0.16 * dot(p, p);
    col = col / (1.0 + col);
    gl_FragColor = vec4(max(col, 0.0), 1.0);
  }
}