public static SparseGraph FloodFill(World world, Vector2D startPosition)
{
var graph = new SparseGraph(false);
var firstNode = new NavGraphNode(
idx: graph.NextNodeIndex,
position: startPosition
);
graph.AddNode(firstNode);
FloodFill(graph: graph, world: world, node: firstNode);
return(graph);
}
private static void FloodFill(SparseGraph graph, World world, NavGraphNode node)
{
/*
* This method should create all edges and neighbouring nodes that are possible
*
* C: Current node
* 1 - 8: Neighbouring nodes for which the edges/nodes should be generated if not colliding with object
* W: Width or space between nodes
*
* 1 -- 2 -- 3
* | \ | / |
* | \ | / |
* 4 -- C -- 5
* | / | \ |
* | / | \ |
* 6 -- 7 -- 8
*
*
* 1 (c.X - W, c.Y - W)
* 2 (c.X , c.Y - W)
* 3 (c.X + W, c.Y - W)
* 4 (c.X - W, c.Y )
* 5 (c.X + W, c.Y )
* 6 (c.X - W, c.Y + W)
* 7 (c.X , c.Y + W)
* 8 (c.X + W, c.Y + W)
*/
List <Vector2D> neighbouringPoints = new List <Vector2D>()
{
new Vector2D(x: node.Position.X - Width, y: node.Position.Y - Width), // 1
new Vector2D(x: node.Position.X, y: node.Position.Y - Width), // 2
new Vector2D(x: node.Position.X + Width, y: node.Position.Y - Width), // 3
new Vector2D(x: node.Position.X - Width, y: node.Position.Y), // 4
new Vector2D(x: node.Position.X + Width, y: node.Position.Y), // 5
new Vector2D(x: node.Position.X - Width, y: node.Position.Y + Width), // 6
new Vector2D(x: node.Position.X, y: node.Position.Y + Width), // 7
new Vector2D(x: node.Position.X + Width, y: node.Position.Y + Width), // 8
};
foreach (var point in neighbouringPoints)
{
// Do not add node if it collides with obstacle and skip to next node
var obstacle = IsObjectInRange(obstacles: world.Obstacles, point: point);
if (obstacle?.Type == ItemType.Block)
{
continue;
}
// Also skip this node if it is outside of the world boundaries
if (point.X < 0 || point.Y < 0 || point.X > world.Width || point.Y > world.Height)
{
continue;
}
// Try to get the neighbouring node and create a new node if it doesn't exist
var neighbour = graph.GetNode(point.X, point.Y) ?? new NavGraphNode(graph.NextNodeIndex, point);
// If the index is equal to the NextNodeIndex, it means that the node was created here and thus should
// be added to the graph. If it isn't equal, we got an existing node from the graph earlier.
var neighbourDidAlreadyExist = neighbour.Index != graph.NextNodeIndex;
if (!neighbourDidAlreadyExist)
{
graph.AddNode(neighbour);
}
// Check if edge exists, and add one if that is not the case
if (!graph.EdgeList.Exists(x => x.From == node.Index && x.To == neighbour.Index))
{
// But also check if the edge doesn't through an object, otherwise it shouldn't be drawn
var obstacleForEdge = IsObjectInRange(
obstacles: world.Obstacles,
point: new Vector2D(
node.Position.X +
((neighbour.Position.X - node.Position.X) /
2), // Take the X-coordinate in the middle of the edge
node.Position.Y +
((neighbour.Position.Y - node.Position.Y) /
2) // Take the Y-coordinate in the middle of the edge
));
if (obstacleForEdge == null || obstacleForEdge?.Type != ItemType.Block)
{
// Add edge in both directions
graph.AddEdge(new GraphEdge(from: node.Index, to: neighbour.Index));
graph.AddEdge(new GraphEdge(from: neighbour.Index, to: node.Index));
}
}
// Go on with the neighbour node, if it didn't exist yet, otherwise skip to the next node
if (neighbourDidAlreadyExist)
{
continue;
}
FloodFill(graph: graph, world: world, node: neighbour);
}
}