unsafe void SplitSubtreesIntoChildrenBinned(ref BinnedResources resources,
int start, int count,
int stagingNodeIndex, ref int stagingNodesCount, out float childrenTreeletsCost)
{
Debug.Assert(count > 2);
FindPartitionBinned(ref resources, start, count, out int splitIndex, out BoundingBox aBounds, out BoundingBox bBounds, out int leafCountA, out int leafCountB);
//Recursion bottomed out.
var stagingNode = resources.StagingNodes + stagingNodeIndex;
var stagingChildren = &stagingNode->A;
ref var a = ref stagingNode->A;
public static unsafe void CreateBinnedResources(BufferPool bufferPool, int maximumSubtreeCount, out RawBuffer buffer, out BinnedResources resources)
{
//TODO: This is a holdover from the pre-BufferPool tree design. It's pretty ugly. While some preallocation is useful (there's no reason to suffer the overhead of
//pulling things out of the BufferPool over and over and over again), the degree to which this preallocates has a negative impact on L1 cache for subtree refines.
int nodeCount = maximumSubtreeCount - 1;
int bytesRequired =
16 * (3 + 3 + 1) + sizeof(BoundingBox) * (maximumSubtreeCount + 3 * nodeCount + 3 * MaximumBinCount) +
16 * (6 + 3 + 8) + sizeof(int) * (maximumSubtreeCount * 6 + nodeCount * 3 + MaximumBinCount * 8) +
16 * (1) + sizeof(Vector3) * maximumSubtreeCount +
16 * (1) + sizeof(SubtreeHeapEntry) * maximumSubtreeCount +
16 * (1) + sizeof(Node) * nodeCount +
16 * (1) + sizeof(int) * nodeCount;
bufferPool.TakeAtLeast(bytesRequired, out buffer);
var memory = buffer.Memory;
int memoryAllocated = 0;
resources.BoundingBoxes = (BoundingBox *)Suballocate(memory, ref memoryAllocated, sizeof(BoundingBox) * maximumSubtreeCount);
resources.LeafCounts = (int *)Suballocate(memory, ref memoryAllocated, sizeof(int) * maximumSubtreeCount);
resources.IndexMap = (int *)Suballocate(memory, ref memoryAllocated, sizeof(int) * maximumSubtreeCount);
resources.Centroids = (Vector3 *)Suballocate(memory, ref memoryAllocated, sizeof(Vector3) * maximumSubtreeCount);
resources.SubtreeHeapEntries = (SubtreeHeapEntry *)Suballocate(memory, ref memoryAllocated, sizeof(SubtreeHeapEntry) * maximumSubtreeCount);
resources.StagingNodes = (Node *)Suballocate(memory, ref memoryAllocated, sizeof(Node) * nodeCount);
resources.RefineFlags = (int *)Suballocate(memory, ref memoryAllocated, sizeof(int) * nodeCount);
resources.SubtreeBinIndicesX = (int *)Suballocate(memory, ref memoryAllocated, sizeof(int) * maximumSubtreeCount);
resources.SubtreeBinIndicesY = (int *)Suballocate(memory, ref memoryAllocated, sizeof(int) * maximumSubtreeCount);
resources.SubtreeBinIndicesZ = (int *)Suballocate(memory, ref memoryAllocated, sizeof(int) * maximumSubtreeCount);
resources.TempIndexMap = (int *)Suballocate(memory, ref memoryAllocated, sizeof(int) * maximumSubtreeCount);
resources.ALeafCountsX = (int *)Suballocate(memory, ref memoryAllocated, sizeof(int) * nodeCount);
resources.ALeafCountsY = (int *)Suballocate(memory, ref memoryAllocated, sizeof(int) * nodeCount);
resources.ALeafCountsZ = (int *)Suballocate(memory, ref memoryAllocated, sizeof(int) * nodeCount);
resources.AMergedX = (BoundingBox *)Suballocate(memory, ref memoryAllocated, sizeof(BoundingBox) * nodeCount);
resources.AMergedY = (BoundingBox *)Suballocate(memory, ref memoryAllocated, sizeof(BoundingBox) * nodeCount);
resources.AMergedZ = (BoundingBox *)Suballocate(memory, ref memoryAllocated, sizeof(BoundingBox) * nodeCount);
resources.BinBoundingBoxesX = (BoundingBox *)Suballocate(memory, ref memoryAllocated, sizeof(BoundingBox) * MaximumBinCount);
resources.BinBoundingBoxesY = (BoundingBox *)Suballocate(memory, ref memoryAllocated, sizeof(BoundingBox) * MaximumBinCount);
resources.BinBoundingBoxesZ = (BoundingBox *)Suballocate(memory, ref memoryAllocated, sizeof(BoundingBox) * MaximumBinCount);
resources.BinLeafCountsX = (int *)Suballocate(memory, ref memoryAllocated, sizeof(int) * MaximumBinCount);
resources.BinLeafCountsY = (int *)Suballocate(memory, ref memoryAllocated, sizeof(int) * MaximumBinCount);
resources.BinLeafCountsZ = (int *)Suballocate(memory, ref memoryAllocated, sizeof(int) * MaximumBinCount);
resources.BinSubtreeCountsX = (int *)Suballocate(memory, ref memoryAllocated, sizeof(int) * MaximumBinCount);
resources.BinSubtreeCountsY = (int *)Suballocate(memory, ref memoryAllocated, sizeof(int) * MaximumBinCount);
resources.BinSubtreeCountsZ = (int *)Suballocate(memory, ref memoryAllocated, sizeof(int) * MaximumBinCount);
resources.BinStartIndices = (int *)Suballocate(memory, ref memoryAllocated, sizeof(int) * MaximumBinCount);
resources.BinSubtreeCountsSecondPass = (int *)Suballocate(memory, ref memoryAllocated, sizeof(int) * MaximumBinCount);
Debug.Assert(memoryAllocated <= buffer.Length, "The allocated buffer should be large enough for all the suballocations.");
}
unsafe void FindPartitionBinned(ref BinnedResources resources, int start, int count,
out int splitIndex, out BoundingBox a, out BoundingBox b, out int leafCountA, out int leafCountB)
{
//Initialize the per-axis candidate maps.
var localIndexMap = resources.IndexMap + start;
BoundingBox centroidBoundingBox;
centroidBoundingBox.Min = resources.Centroids[localIndexMap[0]];
centroidBoundingBox.Max = centroidBoundingBox.Min;
for (int i = 1; i < count; ++i)
{
var centroid = resources.Centroids + localIndexMap[i];
centroidBoundingBox.Min = Vector3.Min(*centroid, centroidBoundingBox.Min);
centroidBoundingBox.Max = Vector3.Max(*centroid, centroidBoundingBox.Max);
}
//Bin along all three axes simultaneously.
var nullBoundingBox = new BoundingBox {
Min = new Vector3(float.MaxValue), Max = new Vector3(float.MinValue)
};
var span = centroidBoundingBox.Max - centroidBoundingBox.Min;
const float epsilon = 1e-12f;
if (span.X < epsilon && span.Y < epsilon && span.Z < epsilon)
{
//All axes are degenerate.
//This is the one situation in which we can end up with all objects in the same bin.
//To stop this, just short circuit.
splitIndex = count / 2;
a = nullBoundingBox;
b = nullBoundingBox;
leafCountA = 0;
leafCountB = 0;
for (int i = 0; i < splitIndex; ++i)
{
BoundingBox.CreateMerged(a, resources.BoundingBoxes[localIndexMap[i]], out a);
leafCountA += resources.LeafCounts[localIndexMap[i]];
}
for (int i = splitIndex; i < count; ++i)
{
BoundingBox.CreateMerged(b, resources.BoundingBoxes[localIndexMap[i]], out b);
leafCountB += resources.LeafCounts[localIndexMap[i]];
}
splitIndex += start;
return;
}
//There is no real value in having tons of bins when there are very few children.
//At low counts, many of them even end up empty.
//You can get huge speed boosts by simply dropping the bin count adaptively.
var binCount = (int)Math.Min(MaximumBinCount, Math.Max(count * .25f, 2));
//Take into account zero-width cases.
//This will result in degenerate axes all being dumped into the first bin.
var inverseBinSize = new Vector3(
span.X > epsilon ? binCount / span.X : 0,
span.Y > epsilon ? binCount / span.Y : 0,
span.Z > epsilon ? binCount / span.Z : 0);
//inverseBinSize = new Vector3(inverseBinSize.X, inverseBinSize.Y, inverseBinSize.Z);
//If the span along an axis is too small, just ignore it.
var maximumBinIndex = new Vector3(binCount - 1);
//Initialize bin information.
for (int i = 0; i < binCount; ++i)
{
resources.BinBoundingBoxesX[i] = nullBoundingBox;
resources.BinBoundingBoxesY[i] = nullBoundingBox;
resources.BinBoundingBoxesZ[i] = nullBoundingBox;
resources.BinSubtreeCountsX[i] = 0;
resources.BinSubtreeCountsY[i] = 0;
resources.BinSubtreeCountsZ[i] = 0;
resources.BinLeafCountsX[i] = 0;
resources.BinLeafCountsY[i] = 0;
resources.BinLeafCountsZ[i] = 0;
}
//var startAllocateToBins = Stopwatch.GetTimestamp();
//Allocate subtrees to bins for all axes simultaneously.
for (int i = 0; i < count; ++i)
{
var subtreeIndex = localIndexMap[i];
var binIndices = Vector3.Min((resources.Centroids[subtreeIndex] - centroidBoundingBox.Min) * inverseBinSize, maximumBinIndex);
var x = (int)binIndices.X;
var y = (int)binIndices.Y;
var z = (int)binIndices.Z;
resources.SubtreeBinIndicesX[i] = x;
resources.SubtreeBinIndicesY[i] = y;
resources.SubtreeBinIndicesZ[i] = z;
var leafCount = resources.LeafCounts + subtreeIndex;
var subtreeBoundingBox = resources.BoundingBoxes + subtreeIndex;
resources.BinLeafCountsX[x] += *leafCount;
resources.BinLeafCountsY[y] += *leafCount;
resources.BinLeafCountsZ[z] += *leafCount;
++resources.BinSubtreeCountsX[x];
++resources.BinSubtreeCountsY[y];
++resources.BinSubtreeCountsZ[z];
BoundingBox.CreateMerged(resources.BinBoundingBoxesX[x], *subtreeBoundingBox, out resources.BinBoundingBoxesX[x]);
BoundingBox.CreateMerged(resources.BinBoundingBoxesY[y], *subtreeBoundingBox, out resources.BinBoundingBoxesY[y]);
BoundingBox.CreateMerged(resources.BinBoundingBoxesZ[z], *subtreeBoundingBox, out resources.BinBoundingBoxesZ[z]);
}
//Determine split axes for all axes simultaneously.
//Sweep from low to high.
var lastIndex = binCount - 1;
resources.ALeafCountsX[0] = resources.BinLeafCountsX[0];
resources.ALeafCountsY[0] = resources.BinLeafCountsY[0];
resources.ALeafCountsZ[0] = resources.BinLeafCountsZ[0];
resources.AMergedX[0] = resources.BinBoundingBoxesX[0];
resources.AMergedY[0] = resources.BinBoundingBoxesY[0];
resources.AMergedZ[0] = resources.BinBoundingBoxesZ[0];
for (int i = 1; i < lastIndex; ++i)
{
var previousIndex = i - 1;
resources.ALeafCountsX[i] = resources.BinLeafCountsX[i] + resources.ALeafCountsX[previousIndex];
resources.ALeafCountsY[i] = resources.BinLeafCountsY[i] + resources.ALeafCountsY[previousIndex];
resources.ALeafCountsZ[i] = resources.BinLeafCountsZ[i] + resources.ALeafCountsZ[previousIndex];
BoundingBox.CreateMerged(resources.AMergedX[previousIndex], resources.BinBoundingBoxesX[i], out resources.AMergedX[i]);
BoundingBox.CreateMerged(resources.AMergedY[previousIndex], resources.BinBoundingBoxesY[i], out resources.AMergedY[i]);
BoundingBox.CreateMerged(resources.AMergedZ[previousIndex], resources.BinBoundingBoxesZ[i], out resources.AMergedZ[i]);
}
//Sweep from high to low.
BoundingBox bMergedX = nullBoundingBox;
BoundingBox bMergedY = nullBoundingBox;
BoundingBox bMergedZ = nullBoundingBox;
int bLeafCountX = 0;
int bLeafCountY = 0;
int bLeafCountZ = 0;
int bestAxis = 0;
float cost = float.MaxValue;
var binSplitIndex = 0;
a = nullBoundingBox;
b = nullBoundingBox;
leafCountA = 0;
leafCountB = 0;
for (int i = lastIndex; i >= 1; --i)
{
int aIndex = i - 1;
BoundingBox.CreateMerged(bMergedX, resources.BinBoundingBoxesX[i], out bMergedX);
BoundingBox.CreateMerged(bMergedY, resources.BinBoundingBoxesY[i], out bMergedY);
BoundingBox.CreateMerged(bMergedZ, resources.BinBoundingBoxesZ[i], out bMergedZ);
bLeafCountX += resources.BinLeafCountsX[i];
bLeafCountY += resources.BinLeafCountsY[i];
bLeafCountZ += resources.BinLeafCountsZ[i];
//It's possible for a lot of bins in a row to be unpopulated. In that event, the metric isn't defined; don't bother calculating it.
float costCandidateX, costCandidateY, costCandidateZ;
if (bLeafCountX > 0 && resources.ALeafCountsX[aIndex] > 0)
{
var metricAX = ComputeBoundsMetric(ref resources.AMergedX[aIndex]);
var metricBX = ComputeBoundsMetric(ref bMergedX);
costCandidateX = resources.ALeafCountsX[aIndex] * metricAX + bLeafCountX * metricBX;
}
else
{
costCandidateX = float.MaxValue;
}
if (bLeafCountY > 0 && resources.ALeafCountsY[aIndex] > 0)
{
var metricAY = ComputeBoundsMetric(ref resources.AMergedY[aIndex]);
var metricBY = ComputeBoundsMetric(ref bMergedY);
costCandidateY = resources.ALeafCountsY[aIndex] * metricAY + bLeafCountY * metricBY;
}
else
{
costCandidateY = float.MaxValue;
}
if (bLeafCountZ > 0 && resources.ALeafCountsZ[aIndex] > 0)
{
var metricAZ = ComputeBoundsMetric(ref resources.AMergedZ[aIndex]);
var metricBZ = ComputeBoundsMetric(ref bMergedZ);
costCandidateZ = resources.ALeafCountsZ[aIndex] * metricAZ + bLeafCountZ * metricBZ;
}
else
{
costCandidateZ = float.MaxValue;
}
if (costCandidateX < costCandidateY && costCandidateX < costCandidateZ)
{
if (costCandidateX < cost)
{
bestAxis = 0;
cost = costCandidateX;
binSplitIndex = i;
a = resources.AMergedX[aIndex];
b = bMergedX;
leafCountA = resources.ALeafCountsX[aIndex];
leafCountB = bLeafCountX;
}
}
else if (costCandidateY < costCandidateZ)
{
if (costCandidateY < cost)
{
bestAxis = 1;
cost = costCandidateY;
binSplitIndex = i;
a = resources.AMergedY[aIndex];
b = bMergedY;
leafCountA = resources.ALeafCountsY[aIndex];
leafCountB = bLeafCountY;
}
}
else
{
if (costCandidateZ < cost)
{
bestAxis = 2;
cost = costCandidateZ;
binSplitIndex = i;
a = resources.AMergedZ[aIndex];
b = bMergedZ;
leafCountA = resources.ALeafCountsZ[aIndex];
leafCountB = bLeafCountZ;
}
}
}
int *bestBinSubtreeCounts;
int *bestSubtreeBinIndices;
switch (bestAxis)
{
case 0:
bestBinSubtreeCounts = resources.BinSubtreeCountsX;
bestSubtreeBinIndices = resources.SubtreeBinIndicesX;
break;
case 1:
bestBinSubtreeCounts = resources.BinSubtreeCountsY;
bestSubtreeBinIndices = resources.SubtreeBinIndicesY;
break;
default:
bestBinSubtreeCounts = resources.BinSubtreeCountsZ;
bestSubtreeBinIndices = resources.SubtreeBinIndicesZ;
break;
}
//Rebuild the index map.
resources.BinStartIndices[0] = 0;
resources.BinSubtreeCountsSecondPass[0] = 0;
for (int i = 1; i < binCount; ++i)
{
resources.BinStartIndices[i] = resources.BinStartIndices[i - 1] + bestBinSubtreeCounts[i - 1];
resources.BinSubtreeCountsSecondPass[i] = 0;
}
//var startIndexMapTime = Stopwatch.GetTimestamp();
for (int i = 0; i < count; ++i)
{
var index = bestSubtreeBinIndices[i];
resources.TempIndexMap[resources.BinStartIndices[index] + resources.BinSubtreeCountsSecondPass[index]++] = localIndexMap[i];
}
//Update the real index map.
for (int i = 0; i < count; ++i)
{
localIndexMap[i] = resources.TempIndexMap[i];
}
//Transform the split index into object indices.
splitIndex = resources.BinStartIndices[binSplitIndex] + start;
}