thebookofshaders/10/matrix.frag

// Author @patriciogv - 2015
// Title: Matrix

#ifdef GL_ES
precision mediump float;
#endif

// Copyright (c) Patricio Gonzalez Vivo, 2015 - http://patriciogonzalezvivo.com/
// I am the sole copyright owner of this Work.
//
// You cannot host, display, distribute or share this Work in any form,
// including physical and digital. You cannot use this Work in any
// commercial or non-commercial product, website or project. You cannot
// sell this Work and you cannot mint an NFTs of it.
// I share this Work for educational purposes, and you can link to it,
// through an URL, proper attribution and unmodified screenshot, as part
// of your educational material. If these conditions are too restrictive
// please contact me and we'll definitely work it out.

uniform vec2 u_resolution;
uniform float u_time;

float random(in float x){ return fract(sin(x)*43758.5453); }
float random(in vec2 st){ return fract(sin(dot(st.xy ,vec2(12.9898,78.233))) * 43758.5453); }

float randomChar(vec2 outer,vec2 inner){
    float grid = 5.;
    vec2 margin = vec2(.2,.05);
    vec2 borders = step(margin,inner)*step(margin,1.-inner);
    vec2 ipos = floor(inner*grid);
    vec2 fpos = fract(inner*grid);
    return step(.5,random(outer*64.+ipos)) * borders.x * borders.y * step(0.01,fpos.x) * step(0.01,fpos.y);
}

void main(){
    vec2 st = gl_FragCoord.st/u_resolution.xy;
    st.y *= u_resolution.y/u_resolution.x;
    vec3 color = vec3(0.0);

    float rows = 1.0;
    // rows = 3.0;
    // rows = 12.0;
    // rows = 24.0;
    vec2 ipos = floor(st*rows);
    vec2 fpos = fract(st*rows);

    ipos += vec2(0.,floor(u_time*20.*random(ipos.x+1.)));

    float pct = 1.0;
    pct *= randomChar(ipos,fpos);
    // pct *= random(ipos);

    color = vec3(pct);

    gl_FragColor = vec4( color , 1.0);
}