Package lejos.robotics.pathfinding

Class FourWayGridMesh

java.lang.Object

lejos.robotics.pathfinding.FourWayGridMesh

All Implemented Interfaces:

NavigationMesh

public class FourWayGridMesh
extends java.lang.Object
implements NavigationMesh

Generates a grid of nodes. Spacing between the grid nodes and clearance around map geometry can be specified. This set can be generated once at the beginning of a user program, and the same node set can be used for all subsequent navigation.

Field Summary

Fields

Modifier and Type	Field and Description
private float	clearance
private float	gridspace
private LineMap	map
private java.util.ArrayList<Node>	mesh

Constructor Summary

Constructors

Constructor and Description
FourWayGridMesh(LineMap map, float gridSpace, float clearance) Instantiates a grid mesh of nodes which won't interconnect between any map geometry.

Method Summary

Modifier and Type	Method and Description
int	addNode(Node node, int neighbors) Adds a node to this set and connects it with a number of neighboring nodes.
boolean	connect(Node node1, Node node2) Attempts to connect two nodes together by adding them as neighbors.
boolean	disconnect(Node node1, Node node2) Disconnects two nodes by removing them as neighbors.
java.util.Collection<Node>	getMesh() Returns a collection of all nodes within this navigation mesh.
void	regenerate() Throws away the previous set of nodes and recalculates them all.
boolean	removeNode(Node node) Removes a node from the set and removes any existing connections with its neighbors.
void	setClearance(float clearance) Changes the safety zone between all nodes/connections and map geometry.
void	setGridSpacing(float gridSpace) Change the size of each grid square.
void	setMap(LineMap map) Feeds this class a new map.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

mesh

private java.util.ArrayList<Node> mesh

map

private LineMap map

clearance

private float clearance

gridspace

private float gridspace

Constructor Detail

FourWayGridMesh

public FourWayGridMesh(LineMap map,
                       float gridSpace,
                       float clearance)

Instantiates a grid mesh of nodes which won't interconnect between any map geometry. Will also keep away the set parameter from map geometry. Grid spacing is adjustable via the constructor.

Parameters:

map - The map containing geometry.

gridSpace - The size of each grid square.

clearance - The safety zone between all nodes/connections and the map geometry.

Method Detail

getMesh

public java.util.Collection<Node> getMesh()

Description copied from interface: NavigationMesh

Returns a collection of all nodes within this navigation mesh.

Specified by:

getMesh in interface NavigationMesh

Returns:

A Collection of Nodes.

setGridSpacing

public void setGridSpacing(float gridSpace)

Change the size of each grid square. NOTE: When grid space value is changed, this class does not regenerate the navigation mesh until regenerate() is explicitly called.

Parameters:

gridSpace - The unit size of each grid square.

setClearance

public void setClearance(float clearance)

Changes the safety zone between all nodes/connections and map geometry. This leaves a margin of error between potential object collisions and the robot. NOTE: When clearance value is changed, this class does not regenerate the navigation mesh until regenerate() is explicitly called.

Parameters:

clearance - The safety clearance between nodes/connections and map geometry.

setMap

public void setMap(LineMap map)

Feeds this class a new map. NOTE: When Map is changed, this class does not regenerate the navigation mesh until regenerate() is explicitly called.

Parameters:

map - The new map data.

regenerate

public void regenerate()

Description copied from interface: NavigationMesh

Throws away the previous set of nodes and recalculates them all. If any setting were changed, such as the spacing between nodes, then it will recalculate them with the new settings.

Specified by:

regenerate in interface NavigationMesh

connect

public boolean connect(Node node1,
                       Node node2)

Description copied from interface: NavigationMesh

Attempts to connect two nodes together by adding them as neighbors. If map data exists for this NavigationMesh, it will check the map data to see if the connection intersects or comes too close to map geometry. If it does they will not be connected and this method returns false.

Specified by:

connect in interface NavigationMesh

Returns:

Boolean value, true if the nodes were connected successfully, false if they could not connect.

disconnect

public boolean disconnect(Node node1,
                          Node node2)

Description copied from interface: NavigationMesh

Disconnects two nodes by removing them as neighbors. If they were not previously connected it returns false.

Specified by:

disconnect in interface NavigationMesh

Returns:

Returns false if they were not previously connected.

addNode

public int addNode(Node node,
                   int neighbors)

Adds a node to this set and connects it with a number of neighboring nodes. If it is unable to find any neighbors it will return 0. This might occur because the node is outside of the bounded area of the map. Note: The most FourWayGridMesh can connect a node to is four. If you select a number larger than four, a maximum of four neighbors will be connected with the node.

Specified by:

addNode in interface NavigationMesh

Parameters:

node - The unconnected node to add to this mesh. Will be connected with others in the set.

neighbors - The maximum number of neighbors to attempt to connect with.

Returns:

the number of neighboring nodes it was able to connect with

removeNode

public boolean removeNode(Node node)

Description copied from interface: NavigationMesh

Removes a node from the set and removes any existing connections with its neighbors. Note: There is no guarantee it is disconnecting from only nodes in this mesh. This method will disconnect the node from all the nodes registered as neighbors.

Specified by:

removeNode in interface NavigationMesh

Parameters:

node - The node to remove.

Returns:

Returns true if the node was removed, false if it did not exist in this set.