circle_wave.shader

#ifdef GL_ES
precision mediump float;
#endif

uniform vec2 u_resolution;
uniform vec2 u_mouse;
uniform float u_time;

float random (in vec2 st) {
    return fract(sin(dot(st.xy, vec2(12.9898,78.233)))* 43758.5453123);
}

float circle(in vec2 _st, in float _radius, in float _border){
    vec2 dist = _st-vec2(0.5);
    return 1.-smoothstep(_radius-(_radius*_border),
                         _radius+(_radius*_border),
                         dot(dist,dist)*4.0);
}

void main(){
    float min_radius = 0.2;
    
    vec2 st = gl_FragCoord.xy/u_resolution.xy;
    st*=16.;
    vec2 ipos = floor(st);
    vec2 fpos = fract(st);

    float wave = abs(cos(u_time + floor(ipos.x) + floor(ipos.y)));
    vec3 color = vec3(circle(fpos,0.9 * (random(ipos) * (1. - min_radius) + min_radius) * wave, 0.2));

    //gl_FragColor = vec4( color, random(ipos) * abs(cos(u_time * (ipos.x) / 4.))* abs(-cos(.21 + u_time / 4. * (ipos.y))) );
    gl_FragColor = vec4( color, 1.0 );
}