NavmeshCut Class Reference

Navmesh cutting is used for fast recast graph updates. More...

Detailed Description

Navmesh cutting is used for fast recast graph updates.

Navmesh cutting is used to cut holes into an existing navmesh generated by a recast graph. Recast 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.

The NavmeshCut component uses a 2D shape to cut the navmesh with. A rectangle and circle shape is built in, but you can also specify a custom mesh to use. 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.

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.

To use a navmesh cut in your scene you need to have a TileHandlerHelper script somewhere in your scene. You should only have one though. That script will take care of checking all the NavmeshCut components to see if they need to update the navmesh.

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 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 extructed 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 useRotation field to true. This is a bit slower, but it is not a very large difference.

A* Pro Feature:

This is an A* Pathfinding Project Pro feature only. This function/class/variable might not exist in the Free version of the A* Pathfinding Project or the functionality might be limited
The Pro version can be bought here

See Also

http://www.arongranberg.com/2013/08/navmesh-cutting/

Public Types
enum	MeshType { Rectangle, Circle, CustomMesh }

Public Member Functions
void	Awake ()
void	ForceUpdate ()
	Forces this navmesh cut to update the navmesh.
Bounds	GetBounds ()
	World space bounds of this cut.
void	GetContour (List< List< Pathfinding.ClipperLib.IntPoint > > buffer)
	World space contour of the navmesh cut.
void	NotifyUpdated ()
	Internal method to notify the NavmeshCut that it has just been used to update the navmesh.
void	OnDestroy ()
void	OnDrawGizmos ()
void	OnDrawGizmosSelected ()
void	OnEnable ()
bool	RequiresUpdate ()
	Returns true if this object has moved so much that it requires an update.
virtual void	UsedForCut ()
	Called whenever this navmesh cut is used to update the navmesh.

Static Public Member Functions
static List< NavmeshCut >	GetAll ()
	Returns a list with all NavmeshCut components in the scene.
static List< NavmeshCut >	GetAllInRange (Bounds b)
	Get all active instances which intersect the bounds.
static Vector3	IntPointToV3 (Pathfinding.ClipperLib.IntPoint p)
	Converts an IntPoint to a Vector3.
static Pathfinding.ClipperLib.IntPoint	V3ToIntPoint (Vector3 p)
	Converts a Vector3 to an IntPoint.

Public Attributes
Vector3	center
float	circleRadius = 1
	Radius of the circle.
int	circleResolution = 6
	Number of vertices on the circle.
bool	cutsAddedGeom = true
	Cuts geometry added by a NavmeshAdd component.
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.
Mesh	mesh
	Custom mesh to use.
float	meshScale = 1
	Scale of the custom mesh, if used.
Vector2	rectangleSize = new Vector2(1, 1)
	Size of the rectangle.
MeshType	type
	Shape of the cut.
float	updateDistance = 0.4f
	Distance between positions to require an update of the navmesh.
float	updateRotationDistance = 10
	How many degrees rotation that is required for an update to the navmesh.
bool	useRotation
	Includes rotation in calculations.

Static Public Attributes
static readonly Color	GizmoColor = new Color(37.0f/255, 184.0f/255, 239.0f/255)

Protected Attributes
Transform	tr
	cached transform component

Properties
Bounds	LastBounds [get]

Events
static System.Action< NavmeshCut >	OnDestroyCallback
	Called every time a NavmeshCut component is destroyed.

Private Member Functions
void	CalculateMeshContour ()

Static Private Member Functions
static void	AddCut (NavmeshCut obj)
static bool	Intersects (Bounds b1, Bounds b2)
	True if b1 and b2 intersects.
static void	RemoveCut (NavmeshCut obj)

Private Attributes
Vector3[][]	contours
Bounds	lastBounds
Mesh	lastMesh
Vector3	lastPosition
Quaternion	lastRotation
bool	wasEnabled

Static Private Attributes
static List< NavmeshCut >	allCuts = new List<NavmeshCut>()
static readonly Dictionary < Int2, int >	edges = new Dictionary<Int2, int>()
	Cached variable, to avoid allocations.
static readonly Dictionary < int, int >	pointers = new Dictionary<int, int>()
	Cached variable, to avoid allocations.

Member Enumeration Documentation

enum MeshType

Enumerator:

Rectangle
Circle
CustomMesh

Member Function Documentation

static void AddCut ( NavmeshCut  obj )

staticprivate

void Awake

(

)

void CalculateMeshContour ( )

private

void ForceUpdate

(

)

Forces this navmesh cut to update the navmesh.

Note

Dynamic updating requires a Tile Handler Helper somewhere in the scene. This update is not instant, it is done the next time the TileHandlerHelper checks this instance for if it needs updating.

See Also

TileHandlerHelper.ForceUpdate()

static List<NavmeshCut> GetAll ( )

static

Returns a list with all NavmeshCut components in the scene.

Warning

Do not modify this array

static List<NavmeshCut> GetAllInRange ( Bounds  b )

static

Get all active instances which intersect the bounds.

Bounds GetBounds

(

)

World space bounds of this cut.

void GetContour

(

List< List< Pathfinding.ClipperLib.IntPoint > >

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.

static bool Intersects ( Bounds  b1, Bounds  b2  )

staticprivate

True if b1 and b2 intersects.

Note

Faster than Unity's built in version. See http://forum.unity3d.com/threads/204243-Slow-Unity-Math-Please-Unity-Tech-keep-core-math-fast?p=1404070#post1404070

static Vector3 IntPointToV3 ( Pathfinding.ClipperLib.IntPoint  p )

static

Converts an IntPoint to a Vector3.

This is a lossy conversion.

void NotifyUpdated

(

)

Internal method to notify the NavmeshCut that it has just been used to update the navmesh.

void OnDestroy

(

)

void OnDrawGizmos

(

)

void OnDrawGizmosSelected

(

)

void OnEnable

(

)

static void RemoveCut ( NavmeshCut  obj )

staticprivate

bool RequiresUpdate

(

)

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.

virtual void UsedForCut ( )

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.

static Pathfinding.ClipperLib.IntPoint V3ToIntPoint ( Vector3  p )

static

Converts a Vector3 to an IntPoint.

This is a lossy conversion.

Member Data Documentation

List<NavmeshCut> allCuts = new List<NavmeshCut>()

staticprivate

Vector3 center

float circleRadius = 1

Radius of the circle.

int circleResolution = 6

Number of vertices on the circle.

Vector3 [][] contours

private

bool cutsAddedGeom = true

Cuts geometry added by a NavmeshAdd component.

You rarely need to change this

readonly Dictionary<Int2, int> edges = new Dictionary<Int2, int>()

staticprivate

Cached variable, to avoid allocations.

readonly Color GizmoColor = new Color(37.0f/255, 184.0f/255, 239.0f/255)

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

Bounds lastBounds

private

Mesh lastMesh

private

Vector3 lastPosition

private

Quaternion lastRotation

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.

readonly Dictionary<int, int> pointers = new Dictionary<int, int>()

staticprivate

Cached variable, to avoid allocations.

Vector2 rectangleSize = new Vector2(1, 1)

Size of the rectangle.

Transform tr

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.

Note

Dynamic updating requires a TileHandlerHelper somewhere in the scene.

float updateRotationDistance = 10

How many degrees rotation that is required for an update to the navmesh.

Should be between 0 and 180.

Note

Dynamic updating requires a Tile Handler Helper somewhere in the scene.

bool useRotation

Includes rotation in calculations.

This is slower since a lot more matrix multiplications are needed but gives more flexibility.

bool wasEnabled

private

Property Documentation

Bounds LastBounds

get

Event Documentation

System.Action<NavmeshCut> OnDestroyCallback

static

Called every time a NavmeshCut component is destroyed.

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The documentation for this class was generated from the following file:

• /Users/arong/Unity/a-pathfinding-project/Assets/AstarPathfindingProject/Navmesh/NavmeshCut.cs