NormalRand

    float nrSpare;
    bool nrSpareReady = false;

    public float NormalRand(float mean, float deviation) {
        if (nrSpareReady) {
            nrSpareReady = false;
            return nrSpare * deviation + mean;
        }
        else {
            float u, v, s;
            while (true) {
                u = Math.Rand(0.0f, 1.0f) * 2.0f - 1.0f;
                v = Math.Rand(0.0f, 1.0f) * 2.0f - 1.0f;
                s = u * u + v * v;
                if (0.0f < s and s < 1.0f)
                    break;
            }
            float mul = Math.Sqrt(-2.0f * RFHumpUtils.Log(s) / s);
            nrSpare = v * mul;
            nrSpareReady = true;
            return mean + deviation * u * mul;
        }
    }