[GLSL] Value Noise

 

https://thebookofshaders.com/11/

The Book of Shaders

 

Vec2-float noise.

#ifdef GL_ES
precision mediump float;
#endif

uniform vec2 u_resolution;

float random(vec2 st){
    float c = fract(sin(dot(st*25., vec2(17.34,50.13)))*84239.523);
    return c;
}

float noise(vec2 st){
    vec2 i = floor(st);
    vec2 f = fract(st);
    
    vec2 v1 = i;
    vec2 v2 = i + vec2(1., 0.);
    vec2 v3 = i + vec2(0., 1.);
    vec2 v4 = i + vec2(1., 1.);
    
    float r1 = random(v1);
    float r2 = random(v2);
    float r3 = random(v3);
    float r4 = random(v4);
    
    f = smoothstep(0., 1., f);
    float bot = mix(r1, r2, f.x);
    float top = mix(r3, r4, f.x);
    float ret = mix(bot, top, f.y);
    
    return ret;
}

void main(){
	vec2 coord = gl_FragCoord.xy/u_resolution;
    coord.x *= u_resolution.x/u_resolution.y;
    coord *= 10.;
	
    vec3 col = vec3(noise(coord));

    gl_FragColor = vec4(col, 1.0); 
}