/// <summary>
///
/// </summary>
/// <param name="worldObject"></param>
/// <returns>A list of all <see cref="GridLocation"/>s containing the <see cref="IWorldObject"/></returns>
public List<GridLocation> Intersects(IWorldObject worldObject)
{
List<GridLocation> found = new List<GridLocation>(gridSize.X * gridSize.Y);
List<GridLocation> missed = new List<GridLocation>(gridSize.X * gridSize.Y);
UniqueList<GridLocation> toTest = new UniqueList<GridLocation>(gridSize.X * gridSize.Y);
UniqueList<GridLocation> newToBeTested = new UniqueList<GridLocation>(gridSize.X * gridSize.Y);
// the GridLocation that contains the center of the object
GridLocation hasCenter;
// STEP 1 - determine the GridLocation of the object's center
Point cellCoord;
// Use integer division to find cell coordinates.
// Since the grid cell coords are in the upperleft corner
// 1 must be subtracted from the division if we are in the negative (left or up)
// direction - effectively rounding up in absolute value.
if (worldObject.Position.X < 0)
cellCoord.X = (Int16)(((Int16)worldObject.Position.X / (Int16)cellSize.X) - 1);
else
cellCoord.X = (Int16)(((Int16)worldObject.Position.X / (Int16)cellSize.X));
if (worldObject.Position.Y < 0)
cellCoord.Y = (Int16)(((Int16)worldObject.Position.Y / (Int16)cellSize.Y) - 1);
else
cellCoord.Y = (Int16)(((Int16)worldObject.Position.Y / (Int16)cellSize.Y));
// check to makes sure these coordinates are in the world
if (minGrid.X <= cellCoord.X && cellCoord.X <= maxGrid.X &&
minGrid.Y <= cellCoord.Y && cellCoord.Y <= maxGrid.Y)
{
hasCenter = new GridLocation((Int16)cellCoord.X,
(Int16)cellCoord.Y,
cellSize);
}
// if they are not in the world, return the empty list
else
{
return found;
}
// add it to the found list
found.Add(hasCenter);
// STEP 2 - determine all surrounding GridLocations that contain the object
toTest.UnionWith(GetSurrounding(hasCenter));
while (toTest.Count != 0)
{
foreach (GridLocation gridLocation in toTest)
{
// if a surrounding GridLocation intersects the object do 4 things
if (worldObject.Bounds.Intersects(gridLocation.Bounds))
{
// 1. Add it to the found list
found.Add(gridLocation);
// 2. Get its surrounding GridLocations
newToBeTested.UnionWith(GetSurrounding(gridLocation));
// 3. Remove any that are already known to not contain the object
foreach (GridLocation g in missed)
{
newToBeTested.Remove(g);
}
// 4. Remove any that are already known to contain the object
foreach (GridLocation g in found)
{
newToBeTested.Remove(g);
}
}
// if a surrounding GridLocation DOES NOT intersect the object add it to missed
else
{
missed.Add(gridLocation);
}
}
// since we have checked everything in toTest flush it
toTest.Clear();
// add the newly found surrounding candidates to toTest
toTest.UnionWith(newToBeTested);
// flush the temp list
newToBeTested.Clear();
}
return found;
}
/// <summary>
/// Requests the <see cref="Grid"/> to return a list of all <see cref="IWorldObject"/>s
/// which share a GridLocation with the given object.
/// </summary>
/// <param name="worldObject"></param>
/// <returns></returns>
public List<IWorldObject> PotentialIntersects(IWorldObject worldObject)
{
UniqueList<IWorldObject> collidables = new UniqueList<IWorldObject>();
// find all grid locations that contain the object
List<GridLocation> IntersectedGridCells = Intersects(worldObject);
foreach (GridLocation gridLocation in IntersectedGridCells)
{
// compile a list of all objects contained in the found Grid Locations
collidables.UnionWith(getLocationObjectsOf(gridLocation));
}
return collidables;
}