Noise2c.frag

#ifdef GL_ES
precision highp float;
#endif

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

// 2D Random
float random (in vec2 st) {
    return fract(sin(dot(st.xy,
                         vec2(12.9898,78.233)))
                 * 43758.5453123);
}

// 2D Noise based on Morgan McGuire @morgan3d
// https://www.shadertoy.com/view/4dS3Wd
float noise (in vec2 st) {
    vec2 i = floor(st);
    vec2 f = fract(st);

    // Four corners in 2D of a tile
    float a = random(i);
    float b = random(i + vec2(1.0, 0.0));
    float c = random(i + vec2(0.0, 1.0));
    float d = random(i + vec2(1.0, 1.0));

    // Smooth Interpolation

    // Cubic Hermine Curve.  Same as SmoothStep()
    vec2 u = f*f*(3.0-2.0*f);
    // u = smoothstep(0.,1.,f);

    // Mix 4 coorners percentages
    return mix(a, b, u.x) +
              (c - a) * u.y * (1.0 - u.x) +
              (d - b) * u.x * u.y;
}

float circle(in vec2 _st, in float _radius){
    vec2 dist = _st-vec2(0.5);
    return 1.-smoothstep(_radius-(_radius*0.01),
                         _radius+(_radius*0.01),
                         dot(dist,dist)*4.0);
}

void main() {
    vec2 st = gl_FragCoord.xy/u_resolution.xy;
    float pct = 0.0;
    vec3 color = vec3(0.0);


    // vec2 translate = vec2(cos(u_time), sin(u_time));
    // st += translate * 0.35;

    vec2 toCenter = vec2(0.5) - st;
    float angle = atan(toCenter.y, toCenter.x);
    float radius = length(toCenter) * 2.0;

    // Use the noise function
    float n = noise(st + radius + sin(u_time));
    n += .2;

     // a. The DISTANCE from the pixel to the center
    pct = distance(st, vec2(n));
    color = vec3(circle(st, pct), .7, .7)/* / angle + n */;
    gl_FragColor = vec4(color, 1.0);
}