export const fragmentSource = `
  precision highp float;
  uniform sampler2D uTexture;
  uniform float uStepH;
  uniform float uNoise;
  uniform float uSeed;
  varying vec2 vTexCoord;
  float rand(vec2 co, float seed, float vScale) {
    return fract(sin(dot(co.xy * vScale ,vec2(12.9898 , 78.233))) * 43758.5453 * (seed + 0.01) / 2.0);
  }
  void main() {
    vec4 color = texture2D(uTexture, vTexCoord);
    color.rgb += (0.5 - rand(vTexCoord, uSeed, 0.1 / uStepH)) * uNoise;
    gl_FragColor = color;
  }
`;