Hi!
I’m trying to use NavMeshClamp script to clamp my character to the Navmesh when using keyboard controls. It works quite well most of the time, but every once in a while it breaks down completely and prints an error message into the console on every frame.
The first case where i noticed this happens is when I open some door. This is likely because there is a NavMeshCut component on them and it modifies the graph. This error floods the console:
NullReferenceException: Object reference not set to an instance of an object
Pathfinding.NavmeshBase.Linecast (Pathfinding.NavmeshBase graph, UnityEngine.Vector3 origin, UnityEngine.Vector3 end, Pathfinding.GraphNode hint, Pathfinding.GraphHitInfo& hit, System.Collections.Generic.List`1[T] trace) (at Assets/AstarPathfindingProject/Generators/NavmeshBase.cs:1242)
Pathfinding.NavmeshBase.Linecast (UnityEngine.Vector3 origin, UnityEngine.Vector3 end, Pathfinding.GraphNode hint, Pathfinding.GraphHitInfo& hit) (at Assets/AstarPathfindingProject/Generators/NavmeshBase.cs:1057)
Pathfinding.NavmeshClamp.LateUpdate () (at Assets/AstarPathfindingProject/ExampleScenes/ExampleScripts/NavmeshClamp.cs:35)
Another case is when I teleport the character to a different graph:
IndexOutOfRangeException: Index was outside the bounds of the array.
Pathfinding.NavmeshTile.GetVertexInGraphSpace (System.Int32 index) (at Assets/AstarPathfindingProject/Generators/Utilities/NavmeshTile.cs:63)
Pathfinding.NavmeshBase.GetVertexInGraphSpace (System.Int32 index) (at Assets/AstarPathfindingProject/Generators/NavmeshBase.cs:176)
Pathfinding.TriangleMeshNode.GetVerticesInGraphSpace (Pathfinding.Int3& v0, Pathfinding.Int3& v1, Pathfinding.Int3& v2) (at Assets/AstarPathfindingProject/Generators/NodeClasses/TriangleMeshNode.cs:105)
Pathfinding.TriangleMeshNode.ClosestPointOnNodeXZInGraphSpace (UnityEngine.Vector3 p) (at Assets/AstarPathfindingProject/Generators/NodeClasses/TriangleMeshNode.cs:146)
Pathfinding.NavmeshBase.Linecast (Pathfinding.NavmeshBase graph, UnityEngine.Vector3 origin, UnityEngine.Vector3 end, Pathfinding.GraphNode hint, Pathfinding.GraphHitInfo& hit, System.Collections.Generic.List`1[T] trace) (at Assets/AstarPathfindingProject/Generators/NavmeshBase.cs:1183)
Pathfinding.NavmeshBase.Linecast (UnityEngine.Vector3 origin, UnityEngine.Vector3 end, Pathfinding.GraphNode hint, Pathfinding.GraphHitInfo& hit) (at Assets/AstarPathfindingProject/Generators/NavmeshBase.cs:1057)
Pathfinding.NavmeshClamp.LateUpdate () (at Assets/AstarPathfindingProject/ExampleScenes/ExampleScripts/NavmeshClamp.cs:35)
Both these errors go away when I change the line 31 in NavmeshClamp script:
var graph = AstarData.GetGraph(prevNode) as IRaycastableGraph;
to
var graph = AstarData.active as IRaycastableGraph;
but it also stops clamping the character correctly to the Navmesh so its not really a fix 
I have also tried looking in the forums and found a few suggestions how to do the navmesh clamping, for example:
transform.position = AstarPath.active.GetNearest(transform.position, NNConstraint.Default).position
This works well on a perfectly flat terrain, but any slopes make the character wiggle vertically a bit. I assume this is because of the difference of height (Y coords) between the navmesh mesh and the actual ground.
Is there some other way (or a fix I can apply to the NavMeshClamp script) I can make navmesh clamping work correctly even with navmesh cuts and teleporting between graphs?
Thanks,
Peter