Circle Mixed With Noise

circle1.c

float quantize(float x, int levels) {
    return select(
        floor(0.5 + x * levels) / levels,
        x, levels < 2);
}

shader circle1(
    point Point = P,
    point Center = 0.0,
    float Radius = 1.5,
    float Blur = 0.05,
    float NoiseWeight = 0.25,
    float Roughness = 2.5,
    color Outside = 0.0,
    color Inside = 1.0,
    int Quantize = 0,
    
    output color Color = 0.8,
    output float Fac = 0.5) {

    vector diff = Center - Point;
    float lenSq = dot(diff, diff);
    float eval = 0.25 * Radius * Radius - lenSq;

    point ptNorm = Roughness * normalize(Point);
    float nVal = noise("usimplex", ptNorm);
    float mxVal = mix(eval, nVal, NoiseWeight);

    float halfBlur = 0.5 * clamp(Blur, 0.0, 1.0);
    Fac = smoothstep(-halfBlur, halfBlur, mxVal);
    Fac = quantize(Fac, Quantize - 1);

    Color = lRgbTosRgb(mix(
        sRgbTolRgb(Outside),
        sRgbTolRgb(Inside),
        Fac));
}