uniform sampler2D uTexNoise;

float noise( vec3 x )
{
  vec3 i = floor(x);
  vec3 f = fract(x);
  f = f*f*(3.0-2.0*f);
  vec2 uv = (i.xy+vec2(37.0,17.0)*i.z) + f.xy;
  vec2 rg = texture( uTexNoise, (uv+0.5)/256.0).yx;
  return mix( rg.x, rg.y, f.z );
}

const mat3 m = mat3( 0.00,  0.80,  0.60,
                    -0.80,  0.36, -0.48,
                    -0.60, -0.48,  0.64 );

float fractalNoise( vec3 x )
{
  vec3 q = 8.0*x;
  float f;
  f  = 0.5000*noise( q ); q = m*q*2.01;
  f += 0.2500*noise( q ); q = m*q*2.02;
  f += 0.1250*noise( q ); q = m*q*2.03;
  f += 0.0625*noise( q ); q = m*q*2.01;
  return f;
}