CCEffect %{
  editor:
    hide: true
  techniques:
  - passes:
    - vert: grid-vs:vert
      frag: grid-fs:frag
      priority: max - 11
      rasterizerState:
        cullMode: none
      depthStencilState:
        depthTest: true
        depthWrite: false
      blendState:
        targets:
        - blend: true
          blendSrc: src_alpha
          blendDst: one_minus_src_alpha
          blendDstAlpha: one_minus_src_alpha
}%

/**
 * a_texCoord.x:
 * 1                                     1
 * +-------------------------------------+
 * |                                     |
 * +-------------------------------------+
 * 0                                     0
 *
 * a_texCoord.y = 0 for lines along Z axis
 * a_texCoord.y = 1 for lines along X axis
 */
CCProgram grid-vs %{
  precision mediump float;
  #include <builtin/uniforms/cc-global>

  in vec2 a_texCoord;
  in vec3 a_position;
  out vec2 uv;
  out vec3 pos_w;

  vec4 vert () {
    uv = a_texCoord;
    pos_w = a_position;
    vec2 forward = vec2(cc_matView[0][2], cc_matView[2][2]);

    // widen the line wrt. camera-plane distance
    float dist = abs(cc_cameraPos.y);
    vec2 scale = vec2(1.0 - a_texCoord.y, a_texCoord.y);
    pos_w.xz += scale * vec2((a_texCoord.x * 2.0 - 1.0) * dist * 0.002);

    vec4 pos = cc_matViewProj * vec4(pos_w, 1.0);
	  pos.z += 0.00011; // nudge on depth to avoid z-fighting at origin
    return pos;
  }
}%

CCProgram grid-fs %{
  precision mediump float;
  #include <builtin/uniforms/cc-global>
  #include <legacy/output>

  in vec2 uv;
  in vec3 pos_w;

  vec4 frag () {
    // alpha wrt. UVs
    float alpha = sqrt(0.5 - abs(uv.x - 0.5));
    // fade out at grazing angles
    float scale = abs(normalize(cc_cameraPos.xyz - pos_w).y);
    if (scale < 0.5) alpha *= max(0.3, scale / 0.5);
    return CCFragOutput(vec4(0.5, 0.5, 0.5, alpha));
  }
}%