/** 直线与圆相交。圆半径和直线的相交点 */
public static Vector3 IntersectionPoint(Vector3 point, Vector3 hit, float radius, Vector3 lineFrom, Vector3 lineTo)
{
float c = radius;
float a = HMath.distance(point, lineFrom, lineTo);
float b = Mathf.Sqrt(c * c - a * a);
return(hit + (lineTo - lineFrom).normalized * b);
}