Sorry for my english.
I use gridgraph. What i want is when player clicked on a point which isn't on the map, the character will move towards that point and stop at the edge of the map. So i use the following method to send a linecast.
bool isBlocked = graph.Linecast((Vector3)start, (Vector3)toEnd, null, out hit);
and use the hit's position.
i expected that hit would return the edge of the map, but instead, it gives me the center.
It will work if there is an unwalkable area at the edge.