Getting a flood fill result given a 2D grid

#1

Hi,

Given a 2D array like bool[100,100] where true is a collision in my 2D game, is there a way to use this asset to provide me with a list of coordinates generated from a flood fill starting at a specific coordinate? This is not really about pathfinding but I think that this asset can be used for such purposes.

In my specific case I just need the neighbours to be adjacent, but I guess diagonal is fine as well.

Thanks!

#2

Hi

You can do that like this:

// This holds all graph data
AstarData data = AstarPath.active.data;

// This creates a Grid Graph
GridGraph gg = data.AddGraph(typeof(GridGraph)) as GridGraph;

// Setup a grid graph with some values
int width = 100;
int depth = 100;
float nodeSize = 1;

gg.center = Vector3.zero;

// Updates internal size from the above values
gg.SetDimensions(width, depth, nodeSize);

// Scans all graphs
AstarPath.active.Scan();

bool[,] walkable =new bool[100,100]; // Fill with whatever

// You can alternatively use gg.GetNode(x, z) and a for loop
gg.GetNodes(n => {
   var node = n as GridNode;
   // Assumes your walkable array is indexed like [y,x] and not [x,y]
   node.Walkable = walkable[node.ZCoordinateInGrid, node.XCoordinateInGrid];
}

// Recalculate all grid connections
// This is required because we have updated the walkability of some nodes
gg.GetNodes(node => gg.CalculateConnections((GridNodeBase)node));

List<GraphNode> floodFillResult = PathUtilities.GetReachableNodes(gg.GetNode(10, 10));
for (int i = 0; i < floodFillResult.Count; i++) {
   var node = floodFillResult[i] as GridNode;
   var x = node.XCoordinateInGrid;
   var z = node.ZCoordinateInGrid;
}

See https://arongranberg.com/astar/docs/pathutilities.html#GetReachableNodes

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