public HitRecord hit(Ray ray, float tmin, floattmax)
{
    float A = ray.getDirection().lengthSquared();
    Vector3f temp1 = new Vector3f(ray.getOrigin());
    temp1.sub(center);
    temp1.scale(2);

    float B = -1 * temp1.dot(ray.getDirection());
    Vector3f temp2 = new Vector3f(ray.getOrigin());
    temp2.sub(center);

    float C = temp2.lengthSquared() - (radius * radius);

    float t1 = (float)((B + Math.sqrt(((B * B) - (4.0f * A * C)))) / (2.0f * A));
    float t2 = (float)((B - Math.sqrt(((B * B) - (4.0f * A * C)))) / (2.0f * A));
    float t = -1;

    if(t1 > tmin) t = t1;

    if((t2 < t) && (t2 > tmin)) t = t2;

    if((t < tmin) || (t > tmax) || (t == Float.NaN)) return null;

    Vector3f normal = new Vector3f(ray.pointAt(t));
    normal.sub(center);

    HitRecord hit = new HitRecord();
    hit.pos = ray.pointAt(t);
    hit.t = t;
    hit.material = material;
    hit.normal = normal;
    hit.normal.normalize();
    return hit;
}