/// <summary>
/// Creates Navigation mesh used for ai
/// </summary>
private void CreateNavMesh()
{
TileCollision currentTileCollision;
TileCollision above, below;
int platformStart = -1;
Platform tempPlatform;
//This steps through each tile looking for valid walking platforms. A valid walking platforms is two passable tiles on an impassable/platform tile
//Once it finds one it stores the edge in a platform object and adds it as a node
for (int y = 0; y < Height; y++)
{
for (int x = 0; x < Width; x++)
{
currentTileCollision = Tiles[y, x].Collision;
if (y - 1 >= 0)
{
above = Tiles[y - 1, x].Collision;
}
else
{
above = TileCollision.Passable;
}
if (y + 1 < Height)
{
below = Tiles[y + 1, x].Collision;
}
else
{
below = TileCollision.Passable;
}
//if current tile is valid for walking on. two passable on top of impassable/platform
if ((currentTileCollision == TileCollision.Passable || currentTileCollision == TileCollision.Platform) &&
(above == TileCollision.Passable || above == TileCollision.Platform) &&
(below == TileCollision.Impassable || below == TileCollision.Platform))
{
if (platformStart == -1)//left edge isn't set yet means new platform!
{
platformStart = x;
}
if (x == Width - 1)//at the end of the map? end the platform
{
tempPlatform = new Platform(platformStart * TileWidth, (x * TileWidth) + TileWidth, (y * TileHeight) + TileHeight);
Platforms.Add(tempPlatform);
NavMesh.AddNode(tempPlatform);
platformStart = -1;
}
}
else if (platformStart != -1)//end of current platform
{
tempPlatform = new Platform(platformStart * TileWidth, x * TileWidth, (y * TileHeight) + TileHeight);
Platforms.Add(tempPlatform);
NavMesh.AddNode(tempPlatform);
platformStart = -1;
}
}
}
ConnectNodes();
}
static public Graph <Platform> FindPath(Platform start, Platform finish)
{
if (navmesh == null)
{
throw new NullReferenceException("No Navigation Mesh Loaded.");
}
GraphNode <Platform> startNode = (GraphNode <Platform>)navmesh.Nodes.FindByValue(start);
GraphNode <Platform> finishNode = (GraphNode <Platform>)navmesh.Nodes.FindByValue(finish);
if (startNode == null || finishNode == null)
{
throw new ArgumentNullException("Start or finish platform is not in nav mesh");
}
Graph <Platform> path = new Graph <Platform>();
Queue <GraphNode <Platform> > frontier = new Queue <GraphNode <Platform> >();
Dictionary <GraphNode <Platform>, GraphNode <Platform> > cameFrom = new Dictionary <GraphNode <Platform>, GraphNode <Platform> >();
GraphNode <Platform> current;
frontier.Enqueue(startNode);
cameFrom.Add(startNode, null);
bool foundIt = false;
while (frontier.Count > 0)
{
current = frontier.Dequeue();
if (current.Equals(finishNode))
{
foundIt = true;
break;
}
foreach (GraphNode <Platform> neighbor in current.Neighbors)
{
if (!cameFrom.ContainsKey(neighbor))
{
cameFrom.Add(neighbor, current);
frontier.Enqueue(neighbor);
}
}
}
if (foundIt == false)
{
return(null);
}
GraphNode <Platform> previous;
current = finishNode;
path.AddNode(current.Value);
while (current != startNode)
{
previous = current;
current = cameFrom[current];
path.AddNode(current.Value);
path.AddDirectedEdge((GraphNode <Platform>)path.Nodes.FindByValue(current.Value), (GraphNode <Platform>)path.Nodes.FindByValue(previous.Value), 1);
}
return(path);
}