/// <summary>
/// Constructor of an edge
/// </summary>
/// <param name="node1">node 1 where node 1 != node 2</param>
/// <param name="node2">node 2 where node 2 != node 1</param>
/// <param name="edgeWeight">Initial weight of the edge ( a higher number is less attractive to the AI )</param>
public Edge(Node node1, Node node2, float edgeWeight)
{
this.node1 = node1;
this.node2 = node2;
distance = (node1.Position - node2.Position).Length(); //precompute heuristic so that the run-time of the game is spead up
weight = edgeWeight;
}
/// <summary>
/// Method to establish connection to another node.
/// </summary>
/// <param name="anotherNode">Node not the same instance as the node the method is invoked on</param>
/// <param name="weightOfConnection">Weight of the established connection (not the distance, but a higher number will result in the edge being less desirable for the AI</param>
/// <param name="distanceToNode">Sets the distance</param>
public void connectToNode(Node anotherNode, float weightOfConnection, float distanceToNode)
{
connectToNode(anotherNode, weightOfConnection);
foreach (Edge e in this.connectedEdges)
if (e.node1 == anotherNode || e.node2 == anotherNode)
e.distance = distanceToNode;
}
/// <summary>
/// Method to establish connection to another node.
/// </summary>
/// <param name="anotherNode">Node not the same instance as the node the method is invoked on</param>
/// <param name="weightOfConnection">Weight of the established connection (not the distance, but a higher number will result in the edge being less desirable for the AI</param>
public void connectToNode(Node anotherNode, float weightOfConnection)
{
if (anotherNode != this)
{
foreach (Edge e in this.connectedEdges)
if (e.node1 == anotherNode || e.node2 == anotherNode)
return; //already connected
Edge conn = new Edge(this, anotherNode, weightOfConnection);
//Bidirectional edge:
connectedEdges.Add(conn);
anotherNode.connectedEdges.Add(conn);
}
}
/// <summary>
/// Method to load a map
/// </summary>
/// <param name="filename">file name of map</param>
/// <param name="contentMgr">content manager instance</param>
/// <param name="gfxDevice">graphics device instance</param>
public static void loadMap(String filename, ContentManager contentMgr, GraphicsDevice gfxDevice)
{
XmlReader reader = XmlReader.Create(filename);
XPathDocument docNav = new XPathDocument(reader);
XPathNavigator nav = docNav.CreateNavigator();
XmlNamespaceManager nsmanager = new XmlNamespaceManager(nav.NameTable);
XPathNodeIterator iter;
XPathNavigator mapIter = nav.SelectSingleNode("/Map");
mapRadius = Convert.ToSingle(mapIter.GetAttribute("mapRadius", nsmanager.DefaultNamespace));
XPathNavigator skyboxIter = nav.SelectSingleNode("/Map/Skybox");
String texName = skyboxIter.GetAttribute("texture", nsmanager.DefaultNamespace);
skyBoxRepeat = Convert.ToSingle(skyboxIter.GetAttribute("repeat", nsmanager.DefaultNamespace));
SetUpSkyBox(gfxDevice, contentMgr, texName, Convert.ToString(skyBoxRepeat));
//Now read in path nodes:
iter = nav.Select("/Map/Marker[@className!='SpawnPoint' and @className!='PlayerSpawnPoint']");
while (iter.MoveNext())
{
Node n = new Node();
readMarkerData(contentMgr, reader, docNav, nav, nsmanager, iter, n);
content.Add(n.id, n);
}
//Read spawnpoints:
iter = nav.Select("/Map/Marker[@className='SpawnPoint']");
while (iter.MoveNext())
{
SpawnPoint n = new SpawnPoint();
readMarkerData(contentMgr, reader, docNav, nav, nsmanager, iter, n);
content.Add(n.id, n);
}
//Read player spawnpoints:
iter = nav.Select("/Map/Marker[@className='PlayerSpawnPoint']");
while (iter.MoveNext())
{
SpawnPoint n = new PlayerSpawnPoint();
readMarkerData(contentMgr, reader, docNav, nav, nsmanager, iter, n);
content.Add(n.id, n);
}
//Now read other content:
iter = nav.Select("/Map/ContentItem");
while (iter.MoveNext())
{
Drawer n = new Drawer(false);
n.contentLoader = contentMgr;
readObjectData(contentMgr, reader, docNav, nav, nsmanager, iter, n);
}
List<Edge> edgeList = new List<Edge>();
List<float> edgeDistances = new List<float>();
iter = nav.Select("/Map/PathEdge");
while (iter.MoveNext())
{
float weight = Convert.ToSingle(iter.Current.GetAttribute("weight", nsmanager.DefaultNamespace));
float distance = Convert.ToSingle(iter.Current.GetAttribute("distance", nsmanager.DefaultNamespace));
String firstId = iter.Current.SelectSingleNode("firstNodeId").Value;
String secondId = iter.Current.SelectSingleNode("secondNodeId").Value;
Node first = null, second = null;
foreach (Object item in content.Values)
if (item is Node)
{
if ((item as Marker).id == firstId)
first = item as Node;
else if ((item as Marker).id == secondId)
second = item as Node;
if (first != null && second != null)
break;
}
edgeList.Add(new Edge(first, second, weight));
edgeDistances.Add(distance);
}
//Connect nodes:
for (int i = 0; i < edgeList.Count; i++)
{
Edge item = edgeList.ElementAt(i);
float distance = edgeDistances.ElementAt(i);
item.node1.connectToNode(item.node2, item.weight, distance);
}
reader.Close();
}
/// <summary>
/// Method to disconnect another node
/// </summary>
/// <param name="otherNode">node to disconnect</param>
public void disconnectFromNode(Node otherNode)
{
if (otherNode == this) return;
Edge foundEdge = null;
foreach (Edge e in this.connectedEdges)
if (e.node1 == otherNode || e.node2 == otherNode)
{
foundEdge = e;
break;
}
if (foundEdge != null)
{
foundEdge.node1.connectedEdges.Remove(foundEdge);
foundEdge.node2.connectedEdges.Remove(foundEdge);
}
}
/// <summary>
/// A* path finding algorithm.
/// </summary>
/// <param name="start">Start node</param>
/// <param name="end">End node</param>
/// <returns>Path to end node if one is found, otherwise null</returns>
public List<Node> AStar(Node start, Node end, bool addRandomFactor)
{
if (start == end || start == null || end == null) return null;
List<Node> openList = new List<Node>();
List<Node> visitedList = new List<Node>();
openList.Add(start);
start.heuristic = (end.Position - start.Position).Length(); //calculate heuristic
while (openList.Count > 0) //while we have more nodes to explore
{
Node bestChoice = openList.ElementAt<Node>(0);
//get the best node choice:
foreach (Node node in openList)
if (bestChoice.pathCost + bestChoice.heuristic > node.pathCost + node.heuristic)
{
bestChoice = node;
break;
}
//move best choice to visited list
visitedList.Add(bestChoice);
bestChoice.hasBeenVisited = true;
openList.Remove(bestChoice);
if (bestChoice == end) //REACHED DESTINATION!!!
{
List<Node> result = new List<Node>();
result.Add(end);
Node it = (end.edgeToPrevNode.node1 == end) ? end.edgeToPrevNode.node2 : end.edgeToPrevNode.node1;
while (it != null)
{
result.Add(it);
if (it.edgeToPrevNode != null)
it = (it.edgeToPrevNode.node1 == it) ? it.edgeToPrevNode.node2 : it.edgeToPrevNode.node1;
else
it = null;
}
//Finally clear node data for the next iteration of the A*:
foreach (Node node in visitedList)
node.clear();
return result;
}
//Not yet at destination so we look at the best choice's neighbours:
foreach (Edge neighbourEdge in bestChoice.connectedEdges)
{
Node neighbour = (neighbourEdge.node1 == bestChoice) ? neighbourEdge.node2 : neighbourEdge.node1;
if (neighbour.hasBeenVisited) continue;
visitedList.Add(neighbour);
Random randomizer = new Random();
double distToNeighbour = bestChoice.pathCost + (addRandomFactor ?
neighbourEdge.distance + neighbourEdge.weight + randomizer.NextDouble() * ASTAR_RANDOM_FACTOR * neighbourEdge.distance : neighbourEdge.distance + neighbourEdge.weight);
double newMoveLength = distToNeighbour + bestChoice.pathCost;
neighbour.heuristic = (neighbour.Position - end.Position).Length();
Boolean shouldMove = false;
if (openList.IndexOf(neighbour) < 0)
{
openList.Add(neighbour);
shouldMove = true;
}
else if (distToNeighbour < neighbour.pathCost)
shouldMove = true;
else
shouldMove = false;
if (shouldMove == true)
{
neighbour.edgeToPrevNode = neighbourEdge;
neighbour.pathCost = distToNeighbour;
}
}
}
return null; //Not found
}
/// <summary>
/// Sets a new path for an object if it is already registered
/// </summary>
/// <param name="AIObject">Any registered dynamic object</param>
/// <param name="start">Start node (should be close to the object if possible)</param>
/// <param name="end">End node</param>
public void setNewPathForRegisteredObject(DynamicObject AIObject, Node start, Node end)
{
if (objectPaths.Keys.Contains(AIObject))
{
List<Node> path = AStar(start, end, AIObject is Destroyer);
if (path != null)
objectPaths[AIObject].remainingPath = path;
else //we just go the the start node
{
path = new List<Node>();
path.Add(start);
objectPaths[AIObject].remainingPath = path;
}
}
}
/// <summary>
/// Method to update remaining path variables when an object reaches its waypoint
/// </summary>
internal void reachedWaypoint()
{
if (objectRemainingPath != null) //if there is a path
{
if (objectRemainingPath.Count > 1) //if we have not reached our destination yet
{
previousNode = objectRemainingPath.Last();
objectRemainingPath.Remove(objectRemainingPath.Last());
currentWaypoint = objectRemainingPath.Last();
calculateCurrentEdge();
}
else //the destination have been reached
{
previousNode = null;
objectRemainingPath.Clear();
currentWaypoint = null;
currentEdge = null;
}
}
}
