///<summary>
///use to add the eight neighboring edges of a graph node that
///is positioned in a grid layout
///</summary>
///<param name="graph"></param>
///<param name="row"></param>
///<param name="col"></param>
///<param name="numCellsX"></param>
///<param name="numCellsY"></param>
public static void AddAllNeighborsToGridNode(
SparseGraph graph,
int row,
int col,
int numCellsX,
int numCellsY)
{
for (int i = -1; i < 2; ++i)
{
for (int j = -1; j < 2; ++j)
{
int nodeX = col + j;
int nodeY = row + i;
//skip if equal to this node
if ((i == 0) && (j == 0)) continue;
//check to see if this is a valid neighbor
if (!ValidNeighbor(nodeX, nodeY, numCellsX, numCellsY))
continue;
//calculate the distance to this node
Vector2 posNode =
graph.GetNode(row*numCellsX + col).Position;
Vector2 posNeighbour =
graph.GetNode(nodeY*numCellsX + nodeX).Position;
float dist = (posNode - posNeighbour).Length();
//this neighbor is okay so it can be added
NavGraphEdge newEdge =
new NavGraphEdge(
row*numCellsX + col,
nodeY*numCellsX + nodeX,
dist);
graph.AddEdge(newEdge);
//if graph is not a digraph, an edge needs to be added going
//in the other direction
if (graph.IsDigraph)
continue;
NavGraphEdge newReverseEdge =
new NavGraphEdge(
nodeY*numCellsX + nodeX,
row*numCellsX + col,
dist);
graph.AddEdge(newReverseEdge);
}
}
}
private bool Search()
{
//create a queue of edges
Queue<NavGraphEdge> queue = new Queue<NavGraphEdge>();
//create a dummy edge and put on the queue
NavGraphEdge dummy = new NavGraphEdge(Source, Source, 0);
queue.Enqueue(dummy);
//mark the source node as visited
Visited[Source] = (int) SearchStatus.Visited;
//while there are edges in the queue keep searching
while (queue.Count > 0)
{
//grab the next edge
NavGraphEdge next = queue.Peek();
//remove the edge from the queue
queue.Dequeue();
//make a note of the parent of the node this edge points to
Route[next.To] = next.From;
//put it on the tree.
//(making sure the dummy edge is not placed on the tree)
if (next != dummy)
{
SpanningTree.Add(next);
}
//if the target has been found the method can return success
if (next.To == Target)
{
return true;
}
//push the edges leading from the node at the end of this edge
//onto the queue
foreach (NavGraphEdge curEdge in Graph.Edges[next.To])
{
if (Visited[curEdge.To] != (int) SearchStatus.Unvisited)
continue;
//if the node hasn't already been visited we can push
//the edge onto the queue
queue.Enqueue(curEdge);
//and mark it visited
Visited[curEdge.To] = (int) SearchStatus.Visited;
}
}
//no path to target
return false;
}
///<summary>
///load graph from map data
///</summary>
///<param name="mapData"></param>
///<returns>true if successful</returns>
public bool Load(MapData mapData)
{
Clear();
//get the number of nodes and read them in
int numNodes = mapData.NodeList.Count;
for (int n = 0; n < numNodes; ++n)
{
NavGraphNode newNode = new NavGraphNode(mapData.NodeList[n]);
//when editing graphs (with Buckland's Raven map editor), it's
//possible to end up with a situation where some of the nodes
//have been invalidated (their id's set to invalid_node_index).
//Therefore when a node of index invalid_node_index is
//encountered, it must still be added.
if (!GraphNode.IsInvalidIndex(newNode.Index))
{
AddNode(newNode);
}
else
{
Nodes.Add(newNode);
//make sure an edgelist is added for each node
Edges.Add(new LinkedList<NavGraphEdge>());
++NextNodeIndex;
}
}
//now add the edges
int numEdges = mapData.EdgeList.Count;
for (int e = 0; e < numEdges; ++e)
{
NavGraphEdge nextEdge = new NavGraphEdge(mapData.EdgeList[e]);
Edges[nextEdge.From].AddLast(nextEdge);
}
return true;
}
///<summary>
///Use this to add an edge to the graph. The method will ensure that the
///edge passed as a parameter is valid before adding it to the graph. If
///the graph is a digraph then a similar edge connecting the nodes in
///the opposite direction will be automatically added.
///</summary>
///<param name="edge"></param>
public void AddEdge(NavGraphEdge edge)
{
//first make sure the from and to nodes exist within the graph
Assert.Fatal((edge.From < NextNodeIndex) &&
(edge.To < NextNodeIndex),
"SparseGraph.AddEdge: invalid node index");
//make sure both nodes are active before adding the edge
if (GraphNode.IsInvalidIndex(Nodes[edge.To].Index) ||
GraphNode.IsInvalidIndex(Nodes[edge.From].Index))
return;
//add the edge, first making sure it is unique
if (UniqueEdge(edge.From, edge.To))
{
Edges[edge.From].AddLast(edge);
}
//if the graph is undirected we must add another connection
//in the opposite direction
if (IsDigraph)
return;
//check to make sure the edge is unique before adding
if (!UniqueEdge(edge.To, edge.From))
return;
NavGraphEdge newEdge = edge;
newEdge.To = edge.From;
newEdge.From = edge.To;
Edges[edge.To].AddLast(newEdge);
}
private bool Search()
{
//create a stack of edges
Stack<NavGraphEdge> stack = new Stack<NavGraphEdge>();
//create a dummy edge and put on the stack
NavGraphEdge dummy = new NavGraphEdge(Source, Source, 0);
stack.Push(dummy);
//while there are edges in the stack keep searching
while (stack.Count > 0)
{
//grab the next edge
NavGraphEdge next = stack.Peek();
//remove the edge from the stack
stack.Pop();
//make a note of the parent of the node this edge points to
Route[next.To] = next.From;
//put it on the tree.
//(making sure the dummy edge is not placed on the tree)
if (next != dummy)
{
SpanningTree.Add(next);
}
//and mark it visited
Visited[next.To] = (int) SearchStatus.Visited;
//if the target has been found the method can return success
if (next.To == Target)
{
return true;
}
//push the edges leading from the node this edge points to onto
//the stack (provided the edge does not point to a previously
//visited node)
foreach (NavGraphEdge curEdge in Graph.Edges[next.To])
{
if (Visited[curEdge.To] == (int) SearchStatus.Unvisited)
{
stack.Push(curEdge);
}
}
}
//no path to target
return false;
}
