public void SplitPlanes()
{
for (int i = 0; i < 100; i++)
{
Vector3 direction = Utils.Random.UnitVector();
float start = (float)Utils.Random.NextDouble();
float end = (float)Utils.Random.NextDouble();
SpatialBin bin = new SpatialBin(direction, start, end);
Assert.AreEqual(direction * start, bin.SplitPlaneLeft.Position);
Assert.AreEqual(direction, bin.SplitPlaneLeft.Normal);
Assert.AreEqual(direction * end, bin.SplitPlaneRight.Position);
Assert.AreEqual(-direction, bin.SplitPlaneRight.Normal);
}
}
public void BoundingBox()
{
Vector3 direction = Vector3.UnitX;
float start = -1f;
float end = 1f;
SpatialBin bin = new SpatialBin(direction, start, end);
for (int i = 0; i < 1000; i++)
{
bin.AABB.Add(Utils.Random.Sphere(0f, 1f));
bin.ClipAndAdd(Utils.Random.Primitive(1f, 3f));
}
Vector3[] bounds = bin.AABB.Bounds;
Assert.AreEqual(-1f, bounds[0].X);
Assert.AreEqual(1f, bounds[1].X);
}
public void Constructor()
{
SpatialBin bin = new SpatialBin(Vector3.UnitX, 0f, 1f);
Assert.IsTrue(bin != null);
}
private SpatialSplit FindSpatialSplit(NodeSpec spec, float nodeSAH)
{
// _bins变量每一次分割都被复用
var origin = spec.bounds.min;
var binSize = (spec.bounds.max - origin) / N_SPATIAL_BINS;
var invBinSize = new Vector3(1f / binSize.x, 1f / binSize.y, 1f / binSize.z);
for (int dim = 0; dim < 3; dim++)
{
for (int i = 0; i < N_SPATIAL_BINS; i++)
{
_bins[dim, i] = SpatialBin.New();
}
}
// 把图元分配到3个维度的bin中
for (int refIdx = _refStack.Count - spec.numRef; refIdx < _refStack.Count; refIdx++)
{
var pRef = _refStack[refIdx];
// ....Vector3Int.FloorToInt 误用了 celling...查半天。。。。
var firstBin = MathUtils.ClampV3Int(Vector3Int.FloorToInt((pRef.bounds.min - origin).Multiply(invBinSize)), Vector3Int.zero, new Vector3Int(N_SPATIAL_BINS - 1, N_SPATIAL_BINS - 1, N_SPATIAL_BINS - 1));
var lastBin = MathUtils.ClampV3Int(Vector3Int.FloorToInt((pRef.bounds.max - origin).Multiply(invBinSize)), firstBin, new Vector3Int(N_SPATIAL_BINS - 1, N_SPATIAL_BINS - 1, N_SPATIAL_BINS - 1));
for (int dim = 0; dim < 3; dim++)
{
var curRef = pRef;
// 从左到右分割,curRef并不更新图元索引，只更新包围盒
for (int i = firstBin[dim]; i < lastBin[dim]; i++)
{
PrimitiveRef leftRef, rightRef;
SplitReference(out leftRef, out rightRef, curRef, dim, origin[dim] + binSize[dim] * (i + 1));
_bins[dim, i].bounds.Union(leftRef.bounds);
curRef = rightRef;
}
_bins[dim, lastBin[dim]].bounds.Union(curRef.bounds); // 分割后图元最右边的包围盒也算进来
// 只对分割后图元所在的第一个和最后一个bin添加图元引用计数
_bins[dim, firstBin[dim]].enter++;
_bins[dim, lastBin[dim]].exit++;
}
}
// 根据分割好的bins，来选择最佳分割平面,跟FindObjectSplit类似,只不过是以bin为单位，而不是图元
SpatialSplit split = SpatialSplit.New();
for (byte dim = 0; dim < 3; dim++)
{
// 从右到左，记录每一种可能的分割后，处在“右边”包围盒的
AABB rightBounds = AABB.New();
for (int i = N_SPATIAL_BINS - 1; i > 0; i--)
{
rightBounds.Union(_bins[dim, i].bounds);
_rightBounds[i - 1] = rightBounds; //_rightBounds用来临时记录右边包围盒的，被复用
}
AABB leftBounds = AABB.New();
int leftNum = 0;
int rightNum = spec.numRef;
for (int i = 1; i < N_SPATIAL_BINS; i++)
{
leftBounds.Union(_bins[dim, i - 1].bounds);
leftNum += _bins[dim, i - 1].enter;
rightNum -= _bins[dim, i - 1].exit;
float sah = nodeSAH + leftBounds.Area * leftNum + _rightBounds[i - 1].Area * rightNum;
if (sah < split.sah)
{
split.sah = sah;
split.dim = dim;
split.pos = origin[dim] + binSize[dim] * i;
}
}
}
return(split);
}
