text: //This file is automatically rebuilt by the Cesium build process.
  define(function() {
      'use strict';
      return "uniform sampler2D colorTexture;\n\
  uniform sampler2D colorTexture2;\n\
  uniform vec2 center;\n\
  uniform float radius;\n\
  varying vec2 v_textureCoordinates;\n\
  void main()\n\
  {\n\
  vec4 color0 = texture2D(colorTexture, v_textureCoordinates);\n\
  vec4 color1 = texture2D(colorTexture2, v_textureCoordinates);\n\
  float x = length(gl_FragCoord.xy - center) / radius;\n\
  float t = smoothstep(0.5, 0.8, x);\n\
  gl_FragColor = mix(color0 + color1, color1, t);\n\
  }\n\
  ";
  });