private MyPath <V> ReturnPath(MyPathfindingData vertexData, MyPathfindingData successor, int remainingVertices)
{
if (vertexData.Predecessor == null)
{
MyPath <V> retval = new MyPath <V>(remainingVertices + 1);
retval.Add(vertexData.Parent as V, successor != null ? (successor.Parent as V) : null);
return(retval);
}
else
{
MyPath <V> retval = ReturnPath(vertexData.Predecessor, vertexData, remainingVertices + 1);
retval.Add(vertexData.Parent as V, successor != null ? (successor.Parent as V) : null);
return(retval);
}
}
private bool Visited(MyPathfindingData vertexData)
{
return(vertexData.Timestamp == m_timestamp);
}
private void Visit(MyPathfindingData vertexData)
{
vertexData.Timestamp = m_timestamp;
}
// Note: Termination criterion tells the pathfinding system, how much we want to terminate the pathfinding in the given vertex.
//
// Values can range from 0.0 to positive infinity. Infinity means that the vertex will never be returned as a result. Zero, on the
// other hand, is equivalent to classical pathfinding, which means that the pathfinding will terminate when a path has been found
// to a vertex with a criterion value of zero and that path's length could not be improved by looking further.
//
// Non-zero values on vertices tell the pathfinding that these vertices are acceptable as final vertices, but only if no better
// vertex is found (i.e. one that would have lower length + heuristic value).
//
// The termination criterion is not used as weighting for the pathfinding priority queue though, which means that you can separate
// termination in a vertex from the searching heuristic
public MyPath <V> FindPath(V start, Func <V, float> heuristic, Func <V, float> terminationCriterion, Predicate <V> vertexTraversable = null, bool returnClosest = true)
{
Debug.Assert(heuristic != null);
Debug.Assert(terminationCriterion != null);
CalculateNextTimestamp();
MyPathfindingData startData = start.PathfindingData;
Visit(startData);
startData.Predecessor = null;
startData.PathLength = 0.0f;
IMyPathVertex <V> retVal = null;
float lowestAcceptableWeight = float.PositiveInfinity;
IMyPathVertex <V> closest = null;
float closestWeight = float.PositiveInfinity;
float terminationValue = terminationCriterion(start);
if (terminationValue != float.PositiveInfinity)
{
retVal = start;
lowestAcceptableWeight = heuristic(start) + terminationValue;
}
m_openVertices.Insert(start.PathfindingData, heuristic(start));
while (m_openVertices.Count > 0)
{
MyPathfindingData currentData = m_openVertices.RemoveMin();
V current = currentData.Parent as V;
float currentPathLength = currentData.PathLength;
if (retVal != null && currentPathLength + heuristic(current) >= lowestAcceptableWeight)
{
break;
}
for (int i = 0; i < current.GetNeighborCount(); ++i)
{
IMyPathEdge <V> edge = current.GetEdge(i);
if (edge == null)
{
continue;
}
V neighbor = edge.GetOtherVertex(current);
if (neighbor == null || (vertexTraversable != null && !vertexTraversable(neighbor)))
{
continue;
}
float newPathLength = currentData.PathLength + edge.GetWeight();
MyPathfindingData neighborData = neighbor.PathfindingData;
float neighborWeight = newPathLength + heuristic(neighbor);
if (neighborWeight < closestWeight)
{
closest = neighbor;
closestWeight = neighborWeight;
}
terminationValue = terminationCriterion(neighbor);
if (neighborWeight + terminationValue < lowestAcceptableWeight)
{
retVal = neighbor;
lowestAcceptableWeight = neighborWeight + terminationValue;
}
if (Visited(neighborData))
{
if (newPathLength < neighborData.PathLength)
{
neighborData.PathLength = newPathLength;
neighborData.Predecessor = currentData;
m_openVertices.ModifyUp(neighborData, neighborWeight);
}
}
else
{
Visit(neighborData);
neighborData.PathLength = newPathLength;
neighborData.Predecessor = currentData;
m_openVertices.Insert(neighborData, neighborWeight);
}
}
}
m_openVertices.Clear();
if (retVal == null)
{
if (returnClosest == false || closest == null)
{
return(null);
}
else
{
return(ReturnPath(closest.PathfindingData, null, 0));
}
}
else
{
return(ReturnPath(retVal.PathfindingData, null, 0));
}
}
public MyPath <V> FindPath(V start, V end, Predicate <V> vertexTraversable = null, Predicate <IMyPathEdge <V> > edgeTraversable = null)
{
// CH: TODO: Make multiple private copies of this method and call the right one
// according to what were the arguments to the public interface method
CalculateNextTimestamp();
MyPathfindingData startData = start.PathfindingData;
Visit(startData);
startData.Predecessor = null;
startData.PathLength = 0.0f;
IMyPathVertex <V> retVal = null;
float shortestPathLength = float.PositiveInfinity;
m_openVertices.Insert(start.PathfindingData, start.EstimateDistanceTo(end));
while (m_openVertices.Count > 0)
{
MyPathfindingData currentData = m_openVertices.RemoveMin();
V current = currentData.Parent as V;
float currentPathLength = currentData.PathLength;
if (retVal != null && currentPathLength >= shortestPathLength)
{
break;
}
for (int i = 0; i < current.GetNeighborCount(); ++i)
{
/*IMyPathVertex<V> neighbor = current.GetNeighbor(i);
* if (neighbor == null) continue;*/
IMyPathEdge <V> edge = current.GetEdge(i);
if (edge == null || (edgeTraversable != null && !edgeTraversable(edge)))
{
continue;
}
V neighbor = edge.GetOtherVertex(current);
if (neighbor == null || (vertexTraversable != null && !vertexTraversable(neighbor)))
{
continue;
}
float newPathLength = currentData.PathLength + edge.GetWeight();
MyPathfindingData neighborData = neighbor.PathfindingData;
if (neighbor == end && newPathLength < shortestPathLength)
{
retVal = neighbor;
shortestPathLength = newPathLength;
}
if (Visited(neighborData))
{
if (newPathLength < neighborData.PathLength)
{
neighborData.PathLength = newPathLength;
neighborData.Predecessor = currentData;
m_openVertices.ModifyUp(neighborData, newPathLength + neighbor.EstimateDistanceTo(end));
}
}
else
{
Visit(neighborData);
neighborData.PathLength = newPathLength;
neighborData.Predecessor = currentData;
m_openVertices.Insert(neighborData, newPathLength + neighbor.EstimateDistanceTo(end));
}
}
}
m_openVertices.Clear();
if (retVal == null)
{
return(null);
}
else
{
return(ReturnPath(retVal.PathfindingData, null, 0));
}
}
