alongLineAngleMoveDistancePt alongLineNormalDir alongLineNormalMoveDistancePt Angle Distance Distance FromPolar GetAngle IsEqual IsLess IsNull Length moveAlongLine Negate Normalize operator* operator* operator*= operator+ operator+ operator+= operator- operator- operator-= operator/ operator/= operator= operator== Perpendicular perpendicularPointOnLine ProjectToLine Rotate Scale Set Sqr Vector2d Vector2d Vector2d Vector2d x y

IsNull() bool IsNull ( double  tolerance = 0.0 ) const 检查向量是否为零向量 检查向量是否为零向量，允许指定容差。 参数 [in] tolerance 容差 返回 如果向量的长度小于容差，返回 true；否则返回 false