/// <summary> Constructor. </summary>
/// <param name="position"> The position of the given chunk. </param>
public Chunk(ChunkCoordinate position)
{
Position = position;
_items = new GridItem[NumberOfGridItemsWide * NumberOfGridItemsHigh];
// TODO do this elsewhere
for (int y = 0; y < NumberOfGridItemsHigh; y++)
{
for (int x = 0; x < NumberOfGridItemsWide; x++)
{
var gridPosition = new GridCoordinate(position, new InnerChunkGridCoordinate(x, y));
var gridItem = GetGridItemAt(gridPosition);
this[gridPosition.InnerChunkGridCoordinate] = gridItem;
}
}
}
/// <summary>
/// Checks the array index/position to verify that it has the correct position information and if
/// it does not, re-reads the data from the world and updates the data.
/// </summary>
/// <param name="index"> The index position to update. </param>
/// <param name="coordinate"> The coordinate representing the position to update. </param>
private void Invalidate(Array2DIndex index, GridCoordinate coordinate)
{
var existingData = _visibleGridItems[index];
if (existingData.Position == coordinate)
{
return;
}
var chunkCoordinate = coordinate.ChunkCoordinate;
if (!_worldGrid.IsValid(chunkCoordinate))
{
return;
}
var chunk = _worldGrid[chunkCoordinate];
var data = chunk[coordinate.InnerChunkGridCoordinate];
UpdateData(index, data, coordinate, chunk);
}
private void ValidateConversion(GridCoordinate gridPosition, Array2DIndex arrayIndex)
{
var worked = ConvertToGridItemIndex(gridPosition).X == arrayIndex.X &&
ConvertToGridItemIndex(gridPosition).Y == arrayIndex.Y;
if (worked)
{
return;
}
// to aid in debugging
worked = ConvertToGridItemIndex(gridPosition).X == arrayIndex.X &&
ConvertToGridItemIndex(gridPosition).Y == arrayIndex.Y;
var message = new StringBuilder();
message.AppendFormat("Array Index ({0}) was converted into Grid Position ({1})", arrayIndex, gridPosition);
message.AppendFormat("But we expected ({0},{1})",
ConvertToGridItemIndex(gridPosition).X,
ConvertToGridItemIndex(gridPosition).Y);
Debug.Log(message);
}
public bool Equals(GridCoordinate other)
{
return(X == other.X && Y == other.Y);
}
/// <summary>
/// Checks the array index/position to verify that it has the correct position information and if
/// it does not, re-reads the data from the world and updates the data.
/// </summary>
/// <param name="coordinate"> The coordinate representing the position to update. </param>
private void InvalidatePosition(GridCoordinate coordinate)
{
Validate(coordinate);
Invalidate(ConvertToGridItemIndex(coordinate), coordinate);
}
/// <summary> Updates the cells that have changed because the target has changed. </summary>
/// <param name="previousCoordinate"> The last position we were at. </param>
private void UpdateChangedUnits(GridCoordinate previousCoordinate)
{
var xDiff = _currentPosition.X - previousCoordinate.X;
var yDiff = _currentPosition.Y - previousCoordinate.Y;
if (xDiff == 0 && yDiff == 0)
{
return;
}
if (Math.Abs(xDiff) >= _visibleGridItems.Width ||
Math.Abs(yDiff) >= _visibleGridItems.Height
)
{
// if we ever move more units than we have, then just invalidate the whole thing.
UpdateAllUnits();
return;
}
// if we're at (x,y) from (x-1, y-1), then (x+halfWidth, y+halfHeight) just came into view (of
// course if we just came from (x+1, y+1), then (x-halfWidth, y-halfWidth) just came into view.
// This used to be `amountToOffsetX = MathUtils.Signed(xDiff, _numUnitsWideHalfThreshold)` but
// then when we moved right it would update the top-right corner one higher than when we moved
// up. I'm not sure why we need to invalidate one higher when moving in the positive direction
// but it seems to work.
//
// My current theory as to why is that it has something to do with one of the conversion
// algorithms preferring the positive direction over the negative.
var amountToOffsetX = xDiff > 0 ? _numUnitsWideHalfThreshold + 1 : -_numUnitsWideHalfThreshold;
var amountToOffsetY = yDiff > 0 ? _numUnitsHighHalfThreshold + 1 : -_numUnitsHighHalfThreshold;
var start = previousCoordinate.Offset(amountToOffsetX, amountToOffsetY);
var end = _currentPosition.Offset(amountToOffsetX, amountToOffsetY);
var startColumn = start.X;
var endColumn = end.X;
// make sure our for loop will work :: )
if (startColumn > endColumn)
{
MathUtils.Swap(ref startColumn, ref endColumn);
}
var startRow = start.Y;
var endRow = end.Y;
if (startRow > endRow)
{
MathUtils.Swap(ref startRow, ref endRow);
}
// OPTIMIZATION 1 - Instead of using PositiveRemainder, we could just have loop through twice
// (when needed) because we know that we can only have to dis-jointed sets of rows[/columns]
//
// OPTIMIZATION 2 - We're currently always hitting the area where the rows/columns overlap
// twice. We could optimize this out (especially if/when we do #1 above).
// update the rows that need to be updated
for (var y = startRow; y < endRow; y++)
{
for (var x = _currentPosition.X - _numUnitsWideHalfThreshold;
x <= _currentPosition.X + _numUnitsWideHalfThreshold;
x++)
{
InvalidatePosition(new GridCoordinate(x, y));
}
}
// update that columns that need to be updated
for (var y = _currentPosition.Y - _numUnitsHighHalfThreshold;
y <= _currentPosition.Y + _numUnitsHighHalfThreshold;
y++)
{
for (var x = startColumn; x < endColumn; x++)
{
InvalidatePosition(new GridCoordinate(x, y));
}
}
}
