internal void UpdateOverlaps(Grid2DSortAndSweep owner) { //Sort along x axis using insertion sort; the list will be nearly sorted, so very few swaps are necessary. for (int i = 1; i < entries.Count; i++) { var entry = entries.Elements[i]; for (int j = i - 1; j >= 0; j--) { if (entry.item.boundingBox.Min.X < entries.Elements[j].item.boundingBox.Min.X) { entries.Elements[j + 1] = entries.Elements[j]; entries.Elements[j] = entry; } else { break; } } } //Sweep the list looking for overlaps. for (int i = 0; i < entries.Count; i++) { Grid2DEntry a = entries.Elements[i]; Grid2DEntry b; //TODO: Microoptimize for (int j = i + 1; j < entries.Count && a.item.boundingBox.Max.X >= (b = entries.Elements[j]).item.boundingBox.Min.X; j++) { if (!(a.item.boundingBox.Min.Y > b.item.boundingBox.Max.Y || a.item.boundingBox.Max.Y < b.item.boundingBox.Min.Y || a.item.boundingBox.Min.Z > b.item.boundingBox.Max.Z || a.item.boundingBox.Max.Z < b.item.boundingBox.Min.Z)) { //Now we know this pair is overlapping, but we do not know if this overlap is already added. //Rather than use a hashset or other heavy structure to check, rely on the rules of the grid. //It's possible to avoid adding pairs entirely unless we are the designated 'responsible' cell. //All other cells will defer to the cell 'responsible' for a pair. //A simple rule for determining the cell which is responsible is to choose the cell which is the //smallest index in the shared cells. So first, compute that cell's index. Int2 minimumSharedIndex = a.previousMin; if (minimumSharedIndex.Y < b.previousMin.Y) { minimumSharedIndex.Y = b.previousMin.Y; } if (minimumSharedIndex.Y > b.previousMax.Y) { minimumSharedIndex.Y = b.previousMax.Y; } if (minimumSharedIndex.Z < b.previousMin.Z) { minimumSharedIndex.Z = b.previousMin.Z; } if (minimumSharedIndex.Z > b.previousMax.Z) { minimumSharedIndex.Z = b.previousMax.Z; } //Is our cell the minimum cell? if (minimumSharedIndex.Y == cellIndex.Y && minimumSharedIndex.Z == cellIndex.Z) { owner.TryToAddOverlap(a.item, b.item); } } } } }
internal static void ComputeCell(ref Vector3f v, out Int2 cell) { cell.Y = (int)Math.Floor(v.Y * cellSizeInverse); cell.Z = (int)Math.Floor(v.Z * cellSizeInverse); }
internal void Initialize(ref Int2 cellIndex, int hash) { this.cellIndex = cellIndex; sortingHash = hash; }