A* Pathfinding Project
4.3.8
The A* Pathfinding Project for Unity 3D
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Navmesh cutting is used for fast recast/navmesh graph updates. More...
Navmesh cutting is used for fast recast/navmesh graph updates.
Navmesh cutting is used to cut holes into an existing navmesh generated by a recast or navmesh graph. Recast/navmesh graphs usually only allow either just changing parameters on existing nodes (e.g make a whole triangle unwalkable) which is not very flexible or recalculate a whole tile which is pretty slow. With navmesh cutting you can remove (cut) parts of the navmesh that is blocked by obstacles such as a new building in an RTS game however you cannot add anything new to the navmesh or change the positions of the nodes. This is significantly faster than recalculating whole tiles from scratch in a recast graph.
The NavmeshCut component uses a 2D shape to cut the navmesh with. A rectangle and a circle shape is built in, but you can also specify a custom mesh to use.
Note that the shape is not 3D so if you rotate the cut you will see that the 2D shape will be rotated and then just projected down on the XZ plane.
In the scene view the NavmeshCut looks like an extruded 2D shape because a navmesh cut also has a height. It will only cut the part of the navmesh which it touches. For performance reasons it only checks the bounding boxes of the triangles in the navmesh, so it may cut triangles whoose bounding boxes it intersects even if the triangle does not intersect the extruded shape. However in most cases this does not make a large difference.
It is also possible to set the navmesh cut to dual mode by setting the isDual field to true. This will prevent it from cutting a hole in the navmesh and it will instead just split the navmesh along the border but keep both the interior and the exterior. This can be useful if you for example want to change the penalty of some region which does not neatly line up with the navmesh triangles. It is often combined with the GraphUpdateScene component (however note that the GraphUpdateScene component will not automatically reapply the penalty if the graph is updated again).
By default the navmesh cut does not take rotation or scaling into account. If you want to do that, you can set the useRotationAndScale field to true. This is a bit slower, but it is not a very large difference.
Custom meshes
For most purposes you can use the built-in shapes, however in some cases a custom cutting mesh may be useful. The custom mesh should be a flat 2D shape like in the image below. The script will then find the contour of that mesh and use that shape as the cut. Make sure that all normals are smooth and that the mesh contains no UV information. Otherwise Unity might split a vertex and then the script will not find the correct contour. You should not use a very high polygon mesh since that will create a lot of nodes in the navmesh graph and slow down pathfinding because of that. For very high polygon meshes it might even cause more suboptimal paths to be generated if it causes many thin triangles to be added to the navmesh.
Control updates through code
Navmesh cuts are applied periodically, but sometimes you may want to ensure the graph is up to date right now. Then you can use the following code.
You can also control how often the scripts check for if any navmesh cut has changed. If you have a very large number of cuts it may be good for performance to not check it as often.
You can also find this setting in the AstarPath inspector under Settings.
Navmesh cutting and tags/penalties
Because navmesh cutting can modify the triangles in the navmesh pretty much abitrarily it is not possible to keep tags and penalties when updating the graph. The tags and penalties will be preserved for nodes which stay exactly the same when an update is applied though.
If you need to use tags, the only stable way to keep them is to apply all the graph updates that set them every time a navmesh cut update has been done. This is of course relatively slow, but it will at least work.
Public Types | |
enum | MeshType { Rectangle, Circle, CustomMesh } |
Public Member Functions | |
override void | ForceUpdate () |
Forces this navmesh cut to update the navmesh. More... | |
void | GetContour (List< List< Vector3 > > buffer) |
World space contour of the navmesh cut. More... | |
void | OnDrawGizmos () |
void | OnDrawGizmosSelected () |
override bool | RequiresUpdate (Pathfinding.Util.GridLookup< NavmeshClipper >.Root previousState) |
Returns true if this object has moved so much that it requires an update. More... | |
virtual void | UsedForCut () |
Called whenever this navmesh cut is used to update the navmesh. More... | |
Public Attributes | |
Vector3 | center |
float | circleRadius = 1 |
Radius of the circle. More... | |
int | circleResolution = 6 |
Number of vertices on the circle. More... | |
bool | cutsAddedGeom = true |
Cuts geometry added by a NavmeshAdd component. More... | |
float | height = 1 |
The cut will be extruded to this height. More... | |
bool | isDual |
Only makes a split in the navmesh, but does not remove the geometry to make a hole. More... | |
Mesh | mesh |
Custom mesh to use. More... | |
float | meshScale = 1 |
Scale of the custom mesh, if used. More... | |
Vector2 | rectangleSize = new Vector2(1, 1) |
Size of the rectangle. More... | |
MeshType | type |
Shape of the cut. More... | |
float | updateDistance = 0.4f |
Distance between positions to require an update of the navmesh. More... | |
float | updateRotationDistance = 10 |
How many degrees rotation that is required for an update to the navmesh. More... | |
bool | useRotationAndScale |
Includes rotation and scale in calculations. More... | |
Static Public Attributes | |
static readonly Color | GizmoColor = new Color(37.0f/255, 184.0f/255, 239.0f/255) |
Protected Member Functions | |
override void | Awake () |
Protected Member Functions inherited from NavmeshClipper | |
virtual void | OnDisable () |
virtual void | OnEnable () |
Protected Member Functions inherited from VersionedMonoBehaviour | |
virtual int | OnUpgradeSerializedData (int version, bool unityThread) |
Handle serialization backwards compatibility. More... | |
virtual void | Reset () |
Handle serialization backwards compatibility. More... | |
Protected Attributes | |
Transform | tr |
cached transform component More... | |
Package Functions | |
override Rect | GetBounds (Pathfinding.Util.GraphTransform inverseTransform) |
Bounds in XZ space after transforming using the *inverse* transform of the inverseTransform parameter. More... | |
float | GetY (Pathfinding.Util.GraphTransform transform) |
Y coordinate of the center of the bounding box in graph space. More... | |
override void | NotifyUpdated (Pathfinding.Util.GridLookup< NavmeshClipper >.Root previousState) |
Internal method to notify the NavmeshCut that it has just been used to update the navmesh. More... | |
Private Member Functions | |
void | CalculateMeshContour () |
void | TransformBuffer (List< Vector3 > buffer, bool reverse) |
Private Attributes | |
Vector3 [][] | contours |
Mesh | lastMesh |
Static Private Attributes | |
static readonly Dictionary< Int2, int > | edges = new Dictionary<Int2, int>() |
Cached variable, to avoid allocations. More... | |
static readonly Dictionary< int, int > | pointers = new Dictionary<int, int>() |
Cached variable, to avoid allocations. More... | |
Additional Inherited Members | |
Static Public Member Functions inherited from NavmeshClipper | |
static void | AddEnableCallback (System.Action< NavmeshClipper > onEnable, System.Action< NavmeshClipper > onDisable) |
static void | RemoveEnableCallback (System.Action< NavmeshClipper > onEnable, System.Action< NavmeshClipper > onDisable) |
Properties inherited from NavmeshClipper | |
static List< NavmeshClipper > | allEnabled [get] |
All navmesh clipper components in the scene. More... | |
Properties inherited from VersionedMonoBehaviour | |
int Util.IEntityIndex. | EntityIndex [get, set] |
Internal entity index used by #BurstBatchHelper. More... | |
Properties inherited from IEntityIndex | |
int | EntityIndex [get, set] |
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protectedvirtual |
Reimplemented from VersionedMonoBehaviour.
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private |
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virtual |
Forces this navmesh cut to update the navmesh.
This update is not instant, it is done the next time it is checked if it needs updating.
Implements NavmeshClipper.
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packagevirtual |
Bounds in XZ space after transforming using the *inverse* transform of the inverseTransform parameter.
The transformation will typically transform the vertices to graph space and this is used to figure out which tiles the cut intersects.
Implements NavmeshClipper.
void GetContour | ( | List< List< Vector3 > > | buffer | ) |
World space contour of the navmesh cut.
Fills the specified buffer with all contours. The cut may contain several contours which is why the buffer is a list of lists.
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package |
Y coordinate of the center of the bounding box in graph space.
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packagevirtual |
Internal method to notify the NavmeshCut that it has just been used to update the navmesh.
Implements NavmeshClipper.
void OnDrawGizmos | ( | ) |
void OnDrawGizmosSelected | ( | ) |
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virtual |
Returns true if this object has moved so much that it requires an update.
When an update to the navmesh has been done, call NotifyUpdated to be able to get relavant output from this method again.
Implements NavmeshClipper.
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private |
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virtual |
Called whenever this navmesh cut is used to update the navmesh.
Called once for each tile the navmesh cut is in. You can override this method to execute custom actions whenever this happens.
Vector3 center |
float circleRadius = 1 |
Radius of the circle.
int circleResolution = 6 |
Number of vertices on the circle.
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private |
bool cutsAddedGeom = true |
Cuts geometry added by a NavmeshAdd component.
You rarely need to change this
Cached variable, to avoid allocations.
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static |
float height = 1 |
The cut will be extruded to this height.
bool isDual |
Only makes a split in the navmesh, but does not remove the geometry to make a hole.
This is slower than a normal cut
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private |
Mesh mesh |
Custom mesh to use.
The contour(s) of the mesh will be extracted. If you get the "max perturbations" error when cutting with this, check the normals on the mesh. They should all point in the same direction. Try flipping them if that does not help.
This mesh should only be a 2D surface, not a volume.
float meshScale = 1 |
Scale of the custom mesh, if used.
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staticprivate |
Cached variable, to avoid allocations.
Vector2 rectangleSize = new Vector2(1, 1) |
Size of the rectangle.
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protected |
cached transform component
MeshType type |
Shape of the cut.
float updateDistance = 0.4f |
Distance between positions to require an update of the navmesh.
A smaller distance gives better accuracy, but requires more updates when moving the object over time, so it is often slower.
float updateRotationDistance = 10 |
How many degrees rotation that is required for an update to the navmesh.
Should be between 0 and 180.
bool useRotationAndScale |
Includes rotation and scale in calculations.
This is slower since a lot more matrix multiplications are needed but gives more flexibility.