engine 延长线到面的交点算法

IConstructMultipoint constructMultipoint = new MultipointClass();
看到这个函数 但是segment1和segment2这两个参数如何赋值呢？
ConstructIntersection(ISegment segment1, esriSegmentExtension extension1, ISegment segment2, esriSegmentExtension extension2, out object params1, out object params2, out object isTangentPoint);