export declare const fbm = "\n  \n  float random (in vec2 st) {\n    return fract(sin(dot(st.xy,\n                        vec2(12.9898,78.233)))*\n        43758.5453123);\n  }\n\n\n  // Based on Morgan McGuire @morgan3d\n  // https://www.shadertoy.com/view/4dS3Wd\n  float noise (in vec2 st) {\n    vec2 i = floor(st);\n    vec2 f = fract(st);\n\n    // Four corners in 2D of a tile\n    float a = random(i);\n    float b = random(i + vec2(1.0, 0.0));\n    float c = random(i + vec2(0.0, 1.0));\n    float d = random(i + vec2(1.0, 1.0));\n\n    vec2 u = f * f * (3.0 - 2.0 * f);\n\n    return mix(a, b, u.x) +\n            (c - a)* u.y * (1.0 - u.x) +\n            (d - b) * u.x * u.y;\n  }\n\n  #define OCTAVES 6\n  float fbm (in vec2 st) {\n    // Initial values\n    float value = 0.0;\n    float amplitude = .5;\n    float frequency = 0.;\n    //\n    // Loop of octaves\n    for (int i = 0; i < OCTAVES; i++) {\n        value += amplitude * noise(st);\n        st *= 2.;\n        amplitude *= .5;\n    }\n    return value;\n  }\n";