GatherNode* GatherTreeBuilder::_Build( vector<GpKdItem>::iterator start, vector<GpKdItem>::iterator end, vector<mdGatherPoint> &points, PathSampler* sampler)
{
assert(end > start);
if (end - start == 1)
return _MakeLeaf(start, points);
BBox<Vec6f> bbox = BBox<Vec6f>(EmptyTy());
for (vector<GpKdItem>::iterator it = start; it != end; it++)
bbox.grow(it->point);
uint32_t dim = maxDim(bbox.size());
vector<GpKdItem>::iterator mid = start + (end - start) / 2;
std::nth_element(start, mid, end, [dim](const GpKdItem &d1, const GpKdItem &d2) -> bool {
return d1.point[dim] < d2.point[dim];
});
GatherNode* node = new GatherNode();
node->left = _Build(start, mid, points, sampler);
node->right = _Build(mid, end, points, sampler);
_UpdateNode(node, sampler);
return node;
}
