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Enable diagonal paths in A* implementation

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The way this works is like so, where 'o' is the voxel we're trying to
leave, '_' is a possible exit, 'x' is an obstacle, and * is the exit.

    __*
    _o_
    ___

    xx*
    _o_
    ___

    xxx
    _o*
    ___

    xx_
    _ox
    __*

Basically, if both the north and east paths are available, AND the
northeast path is available, we use the northeast path.
This commit is contained in:
Drew DeVault 2015-07-02 17:52:55 -06:00
parent b56a53dc81
commit 2edd199fca
1 changed files with 43 additions and 3 deletions
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46
TrueCraft.Core/AI/AStarPathFinder.cs
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@ -15,6 +15,14 @@ namespace TrueCraft.Core.AI
Coordinates3D.West
};
private readonly Coordinates3D[][] DiagonalNeighbors = new Coordinates3D[][]
{
new[] { Coordinates3D.North, Coordinates3D.East },
new[] { Coordinates3D.North, Coordinates3D.West },
new[] { Coordinates3D.South, Coordinates3D.East },
new[] { Coordinates3D.South, Coordinates3D.West },
};
private PathResult TracePath(Coordinates3D start, Coordinates3D goal, Dictionary<Coordinates3D, Coordinates3D> parents)
{
var list = new List<Coordinates3D>();
@ -28,6 +36,13 @@ namespace TrueCraft.Core.AI
return new PathResult { Waypoints = list };
}
private bool CanOccupyVoxel(IWorld world, BoundingBox box, Coordinates3D voxel)
{
var id = world.GetBlockID(voxel);
// TODO: Make this more sophisticated
return id == 0;
}
public PathResult FindPath(IWorld world, BoundingBox subject, Coordinates3D start, Coordinates3D goal)
{
// Thanks to www.redblobgames.com/pathfinding/a-star/implementation.html
@ -49,15 +64,40 @@ namespace TrueCraft.Core.AI
closedset.Add(current);
// Test directly adjacent voxels
for (int i = 0; i < Neighbors.Length; i++)
{
var next = Neighbors[i] + current;
if (closedset.Contains(next))
continue;
var id = world.GetBlockID(next);
if (id != 0)
continue; // TODO: Make this more sophisticated
if (!CanOccupyVoxel(world, subject, next))
continue;
var cost = (int)(costs[current] + current.DistanceTo(next));
if (!costs.ContainsKey(next) || cost < costs[next])
{
costs[next] = cost;
var priority = cost + next.DistanceTo(goal);
openset.Enqueue(next, priority);
parents[next] = current;
}
}
// Test diagonally
for (int i = 0; i < DiagonalNeighbors.Length; i++)
{
var pair = DiagonalNeighbors[i];
var next = pair[0] + pair[1] + current;
if (closedset.Contains(next))
continue;
if (!CanOccupyVoxel(world, subject, next))
continue;
if (!CanOccupyVoxel(world, subject, pair[0] + current))
continue;
if (!CanOccupyVoxel(world, subject, pair[1] + current))
continue;
var cost = (int)(costs[current] + current.DistanceTo(next));
if (!costs.ContainsKey(next) || cost < costs[next])