// Copyright (c) 2017-2020 Xiamen Yaji Software Co., Ltd.
CCEffect %{
  editor:
    hide: true
  techniques:
  - name: transparent
    passes:
    - vert: terrain-brush-vs:vert
      frag: terrain-brush-fs:frag
      depthStencilState:
        depthTest: true
        depthWrite: false
      blendState:
        targets:
        - blend: true
          blendSrc: src_alpha
          blendDst: one_minus_src_alpha
          blendDstAlpha: one_minus_src_alpha
      properties:
        BrushPos:         { value: [0, 0, 0, 1] }
        BrushParams:      { value: [2.5, 2.5, 0, 0] }
        BrushDepthOffset: { value: 0.05 }
}%

CCProgram terrain-brush-vs %{
  precision mediump float;
  #include <builtin/uniforms/cc-global>
  #include <builtin/uniforms/cc-local>

  in vec3 a_position;

  out vec4 wposition;

  uniform Constant {
    float BrushDepthOffset;
  };

  vec4 vert () {
    vec3 worldPos;
    worldPos.x = cc_matWorld[3][0] + a_position.x;
    worldPos.y = cc_matWorld[3][1] + a_position.y;
    worldPos.z = cc_matWorld[3][2] + a_position.z;
    worldPos.y += BrushDepthOffset; // depth increment for terrain brushes

    vec4 pos = vec4(worldPos, 1);
    pos = cc_matViewProj * pos;

    wposition = vec4(worldPos, 1);

    return pos;
  }
}%

CCProgram terrain-brush-fs %{
  precision mediump float;
  #include <legacy/output>

  in vec4 wposition;

  uniform TexCoords {
    vec4 BrushPos;
    vec4 BrushParams;
  };

  vec4 frag () {
    float Radius = BrushParams.x;
    float Falloff = BrushParams.y;
    float Distance = length(wposition.xz - BrushPos.xz);

    float k = 0.0;
    #if LINEAR
      if (Distance <= Radius) {
        k = 1.0;
      }
      else if (Distance > Radius + Falloff) {
        k = 0.0;
      }
      else {
        k = max(0.0, 1.0 - (Distance - Radius) / Falloff);
      }
    #elif SMOOTH
      if (Distance <= Radius) {
        k = 1.0;
      }
      else if (Distance > Radius + Falloff) {
        k = 0.0;
      }
      else {
        float y = (Distance - Radius) / Falloff;
        k = sqrt(1.0 - y * y);
      }
    #elif SPHERICAL
      if (Distance <= Radius) {
        k = 1.0;
      }
      else if (Distance > Radius + Falloff) {
        k = 0.0;
      }
      else {
        k = max(0.0, 1.0 - (Distance - Radius) / Falloff);
      }

      k = k*k*(3.0 - 2.0 * k);
    #elif TIP
      if (Distance <= Radius) {
        k = 1.0;
      }
      else if (Distance > Radius + Falloff) {
        k = 0.0;
      }
      else {
        float y = (Falloff + Radius - Distance) / Falloff;

        k = 1.0 - sqrt(1.0 - y * y);
      }
    #endif

    vec4 color = vec4(0.0, 0.0, 0.0, 1.0);
    color.rgb = vec3(100, 100, 135) / 255.0;
    color.a = 0.85 * k;

    return CCFragOutput(color);
  }
}%