shader-useful-function

fragment.glsl

uniform vec2 u_resolution;

// 接受一个二维向量，返回一个伪随机值
float rand(const vec2 seed) {
  float t = dot(vec2(12.9898, 78.233), seed);
  return fract(sin(t) * (4375.85453 + t));
}

void main() {
  vec2 st = gl_FragCoord.xy / u_resolution.xy;
  float rnd = random( st );
  gl_FragColor = vec4(vec3(rnd),1.0);
}

https://thebookofshaders.com/10/