[GLSL] Fractal Brownian Motion

 

https://thebookofshaders.com/13/

The Book of Shaders

 

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float amplitude = 1.;
float frequency = 1.;
y = sin(x * frequency);
float t = 0.01*(-u_time*130.0);
y += sin(x*frequency*2.1 + t)*4.5;
y += sin(x*frequency*1.72 + t*1.121)*4.0;
y += sin(x*frequency*2.221 + t*0.437)*5.0;
y += sin(x*frequency*3.1122+ t*4.269)*2.5;
y *= amplitude*0.06;

#ifdef GL_ES
precision mediump float;
#endif

uniform vec2 u_resolution;
uniform float u_time;

vec2 random(vec2 st){
    float x = fract(sin(dot(st, vec2(75.8,48.6)))*1e5);
    float y = fract(cos(dot(st, vec2(28.13,39.49)))*1e5);
    
    return vec2(x, y) *2. -1.;
}

float noise(vec2 st){
    vec2 i = floor(st);
    vec2 f = fract(st);
    
    f = f*f*f*(f*(f*6.-15.)+10.);
    
    vec2 v1 = i;
    vec2 v2 = i + vec2(1., 0.);
    vec2 v3 = i + vec2(0., 1.);
    vec2 v4 = i + vec2(1., 1.);
    
    vec2 r1 = random(v1);
    vec2 r2 = random(v2);
    vec2 r3 = random(v3);
    vec2 r4 = random(v4);
    
    float d1 = dot(r1, st-v1);
    float d2 = dot(r2, st-v2);
    float d3 = dot(r3, st-v3);
    float d4 = dot(r4, st-v4);
    
    float bot = mix(d1, d2, f.x);
    float top = mix(d3, d4, f.x);
    float ret = mix(bot, top, f.y);
    
    return ret*0.5+0.5;
}

float fbm(vec2 st){
    float value = 0.0;
    float amp = 0.5;
    float frq = 0.0;
    
    const int octave = 6;
    
    for (int i=0; i<octave; i++){
        value += amp * noise(st);
        amp *= 0.5;
        st *= 2.0;
    }
    
    return value;
}

void main(){
	vec2 coord = gl_FragCoord.xy/u_resolution;
    coord.x *= u_resolution.x/u_resolution.y;
    
    vec3 col = vec3(fbm(coord*6.000));
    gl_FragColor = vec4(col, 1.0); 
}