// Copyright (c) 2017-2018 Xiamen Yaji Software Co., Ltd.

CCEffect %{
  techniques:
  - passes:
    - vert: vs
      frag: fs
      blendState:
        targets:
        - blend: true
      rasterizerState:
        cullMode: none
      properties:
        scale: { value: 20 }
        smoothness: { value: 0.1 }
        seed: { value: 12.9898 }
        time: { value: 0 }
}%


CCProgram vs %{
  precision highp float;

  #include <cc-global>
  #include <cc-local>

  in vec3 a_position;
  in vec4 a_color;
  out vec4 v_color;

  #if USE_TEXTURE
  in vec2 a_uv0;
  out vec2 v_uv0;
  #endif

  void main () {
    vec4 pos = vec4(a_position, 1);

    #if CC_USE_MODEL
    pos = cc_matViewProj * cc_matWorld * pos;
    #else
    pos = cc_matViewProj * pos;
    #endif

    #if USE_TEXTURE
    v_uv0 = a_uv0;
    #endif

    v_color = a_color;

    gl_Position = pos;
  }
}%


CCProgram fs %{
  precision highp float;
  uniform sampler2D texture;
  uniform sampler2D texture2;
  uniform Perlin {
    float scale;
    float smoothness;
    float seed;
    float time;
  };
  float progress = time;
  in mediump vec2 v_uv0;
  in vec4 v_color;

  // http://byteblacksmith.com/improvements-to-the-canonical-one-liner-glsl-rand-for-opengl-es-2-0/
  float random(vec2 co) {
    highp float a = seed;
    highp float b = 78.233;
    highp float c = 43758.5453;
    highp float dt= dot(co.xy ,vec2(a,b));
    highp float sn= mod(dt,3.14);
    return fract(sin(sn) * c);
  }

  // 2D Noise based on Morgan McGuire @morgan3d
  // https://www.shadertoy.com/view/4dS3Wd
  float noise (in vec2 st) {
    vec2 i = floor(st);
    vec2 f = fract(st);

    // Four corners in 2D of a tile
    float a = random(i);
    float b = random(i + vec2(1.0, 0.0));
    float c = random(i + vec2(0.0, 1.0));
    float d = random(i + vec2(1.0, 1.0));

    // Cubic Hermine Curve. Same as SmoothStep
    vec2 u = f*f*(3.0-2.0*f);

    // Mix 4 coorners porcentages
    return mix(a, b, u.x) +
            (c - a)* u.y * (1.0 - u.x) +
            (d - b) * u.x * u.y;
  }

  vec4 getFromColor(vec2 uv) {
    return texture(texture, uv);
  }
  vec4 getToColor(vec2 uv) {
    return texture(texture2, uv);
  }

  vec4 transition (vec2 uv) {
    vec4 from = getFromColor(uv);
    vec4 to = getToColor(uv);
    float n = noise(uv * scale);

    float p = mix(-smoothness, 1.0 + smoothness, progress);
    float lower = p - smoothness;
    float higher = p + smoothness;

    // 根据噪声值进行平滑插值
    float q = smoothstep(lower, higher, n);

    return mix(
        from,
        to,
        1.0 - q
      );
  }

  void main () {
    gl_FragColor = v_color * transition(v_uv0);
  }
}%