resources/particles/swirl.json

{
   "MaxCount": 4096,
   "Duration": 1,
   "Rate": 400,
   "Drawable": {
      "Type": "SkCircleDrawable",
      "Radius": 2
   },
   "Code": [
      "// float rand; Every read returns a random float [0 .. 1)",
      "layout(ctype=float) in uniform float dt;",
      "layout(ctype=float) in uniform float effectAge;",
      "",
      "struct Particle {",
      "  float  age;",
      "  float  lifetime;",
      "  float2 pos;",
      "  float2 dir;",
      "  float  scale;",
      "  float2 vel;",
      "  float  spin;",
      "  float4 color;",
      "  float  frame;",
      "};",
      "",
      "void spawn(inout Particle p) {",
      "  p.lifetime = 1 + 2 * rand;",
      "  p.pos.x = rand * 50;",
      "  float a = radians(-10 + 20 * rand);",
      "  float s = 50 + 10 * rand;",
      "  p.vel.x = sin(a) * s;",
      "  p.vel.y = -cos(a) * s;",
      "}",
      "",
      "void update(inout Particle p) {",
      "  p.vel.x += wind(p.age) * dt;",
      "  p.scale = 3 - (1.5 * p.age);",
      "  p.color = color(p.age);",
      "}",
      ""
   ],
   "Bindings": [
      {
         "Type": "SkCurveBinding",
         "Name": "wind",
         "Curve": {
            "XValues": [],
            "Segments": [
               {
                  "Type": "Cubic",
                  "Ranged": false,
                  "Bidirectional": true,
                  "A0": 180,
                  "B0": -90,
                  "C0": -120,
                  "D0": -200
               }
            ]
         }
      },
      {
         "Type": "SkColorCurveBinding",
         "Name": "color",
         "Curve": {
            "XValues": [],
            "Segments": [
               {
                  "Type": "Linear",
                  "Ranged": true,
                  "A0": [ 1, 0, 0, 1 ],
                  "D0": [ 1, 0.735294, 0, 1 ],
                  "A1": [ 1, 0.588235, 0, 1 ],
                  "D1": [ 0.941177, 1, 0, 1 ]
               }
            ]
         }
      }
   ]
}