1、二维情况下，计算多边形面积

 internal static float GetArea(List<Vector2> points)
{float area2 = 0;for (int numPoint = 0; numPoint < points.Count - 1; numPoint++){MyPoint point = points[numPoint];MyPoint nextPoint = points[numPoint + 1];area2 += point.x * nextPoint.y - point.y * nextPoint.x;}return area2 / 2f;
}

2、三维情况下，计算多边形面积

 internal static float GetArea3D(List<Vector3> points, Vector3 normal){Vector3 vector = Vector3.zero;for (int numPoint = 0; numPoint < points.Count - 1; numPoint++){var point = points[numPoint];var nextPoint = points[numPoint + 1];vector += Vector3.Cross(point, nextPoint);}return (1f / 2f) * Math.Abs(Vector3.Dot(vector, normal));}