text: const fxaa = `
  #define FXAA_SPAN_MAX 8.0
  #define FXAA_REDUCE_MUL   (1.0/FXAA_SPAN_MAX)
  #define FXAA_REDUCE_MIN   (1.0/128.0)
  #define FXAA_SUBPIX_SHIFT (1.0/4.0)
  vec3 fxaa(sampler2D tex, vec2 uv) {
  
    vec2 rcpFrame = 1. / resolution;
    vec4 aauv = vec4( uv, uv - (rcpFrame * (0.5 + FXAA_SUBPIX_SHIFT)));
  
    vec3 rgbNW = texture2D(tex, aauv.zw ).xyz;
    vec3 rgbNE = texture2D(tex, aauv.zw + vec2(1,0)*rcpFrame.xy ).xyz;
    vec3 rgbSW = texture2D(tex, aauv.zw + vec2(0,1)*rcpFrame.xy ).xyz;
    vec3 rgbSE = texture2D(tex, aauv.zw + vec2(1,1)*rcpFrame.xy ).xyz;
    vec3 rgbM  = texture2D(tex, aauv.xy ).xyz;
    vec3 luma = vec3(0.299, 0.587, 0.114);
    float lumaNW = dot(rgbNW, luma);
    float lumaNE = dot(rgbNE, luma);
    float lumaSW = dot(rgbSW, luma);
    float lumaSE = dot(rgbSE, luma);
    float lumaM  = dot(rgbM,  luma);
    float lumaMin = min(lumaM, min(min(lumaNW, lumaNE), min(lumaSW, lumaSE)));
    float lumaMax = max(lumaM, max(max(lumaNW, lumaNE), max(lumaSW, lumaSE)));
    vec2 dir;
    dir.x = -((lumaNW + lumaNE) - (lumaSW + lumaSE));
    dir.y =  ((lumaNW + lumaSW) - (lumaNE + lumaSE));
    float dirReduce = max(
        (lumaNW + lumaNE + lumaSW + lumaSE) * (0.25 * FXAA_REDUCE_MUL),
        FXAA_REDUCE_MIN);
    float rcpDirMin = 1.0/(min(abs(dir.x), abs(dir.y)) + dirReduce);
    dir = min(vec2( FXAA_SPAN_MAX,  FXAA_SPAN_MAX),
          max(vec2(-FXAA_SPAN_MAX, -FXAA_SPAN_MAX),
          dir * rcpDirMin)) * rcpFrame.xy;
    vec3 rgbA = (1.0/2.0) * (
        texture2D(tex, aauv.xy + dir * (1.0/3.0 - 0.5) ).xyz +
        texture2D(tex, aauv.xy + dir * (2.0/3.0 - 0.5) ).xyz);
    vec3 rgbB = rgbA * (1.0/2.0) + (1.0/4.0) * (
        texture2D(tex, aauv.xy + dir * (0.0/3.0 - 0.5) ).xyz +
        texture2D(tex, aauv.xy + dir * (3.0/3.0 - 0.5) ).xyz);
    float lumaB = dot(rgbB, luma);
    if((lumaB < lumaMin) || (lumaB > lumaMax)) return rgbA;
    return rgbB;
  }
  `;
  
  export default fxaa;
  