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uniform sampler2D texture1;

uniform sampler2D texture2;

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uniform sampler2D noiseTexture;

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const float threshold = 0.5;

const float range = 0.2;

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varying vec2 pos;

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void main() {

  vec4 colour1 = texture2D(texture1, pos);

  vec4 colour2 = texture2D(texture2, pos);

  float noise = texture2D(noiseTexture, pos).r;

  float t = smoothstep(threshold - range, threshold + range, noise);

  gl_FragColor = mix(colour1, colour2, t);

}

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