void BVHObjectSplit::split(BVHBuild *builder, BVHRange& left, BVHRange& right, const BVHRange& range)
{
/* sort references according to split */
bvh_reference_sort(range.start(), range.end(), &builder->references[0], this->dim);
/* split node ranges */
left = BVHRange(this->left_bounds, range.start(), this->num_left);
right = BVHRange(this->right_bounds, left.end(), range.size() - this->num_left);
}
CCL_NAMESPACE_BEGIN
/* Object Split */
BVHObjectSplit::BVHObjectSplit(BVHBuild *builder,
BVHSpatialStorage *storage,
const BVHRange& range,
vector<BVHReference> *references,
float nodeSAH)
: sah(FLT_MAX),
dim(0),
num_left(0),
left_bounds(BoundBox::empty),
right_bounds(BoundBox::empty),
storage_(storage),
references_(references)
{
const BVHReference *ref_ptr = &references_->at(range.start());
float min_sah = FLT_MAX;
for(int dim = 0; dim < 3; dim++) {
/* Sort references. */
bvh_reference_sort(range.start(),
range.end(),
&references_->at(0),
dim);
/* sweep right to left and determine bounds. */
BoundBox right_bounds = BoundBox::empty;
storage_->right_bounds.resize(range.size());
for(int i = range.size() - 1; i > 0; i--) {
right_bounds.grow(ref_ptr[i].bounds());
storage_->right_bounds[i - 1] = right_bounds;
}
/* sweep left to right and select lowest SAH. */
BoundBox left_bounds = BoundBox::empty;
for(int i = 1; i < range.size(); i++) {
left_bounds.grow(ref_ptr[i - 1].bounds());
right_bounds = storage_->right_bounds[i - 1];
float sah = nodeSAH +
left_bounds.safe_area() * builder->params.primitive_cost(i) +
right_bounds.safe_area() * builder->params.primitive_cost(range.size() - i);
if(sah < min_sah) {
min_sah = sah;
this->sah = sah;
this->dim = dim;
this->num_left = i;
this->left_bounds = left_bounds;
this->right_bounds = right_bounds;
}
}
}
}
BVHSpatialSplitBuildTask(BVHBuild *build,
InnerNode *node,
int child,
const BVHRange& range,
const vector<BVHReference>& references,
int level)
: range_(range),
references_(references.begin() + range.start(),
references.begin() + range.end())
{
range_.set_start(0);
run = function_bind(&BVHBuild::thread_build_spatial_split_node,
build,
node,
child,
&range_,
&references_,
level,
_1);
}
void BVHSpatialSplit::split(BVHBuild *builder,
BVHRange& left,
BVHRange& right,
const BVHRange& range)
{
/* Categorize references and compute bounds.
*
* Left-hand side: [left_start, left_end[
* Uncategorized/split: [left_end, right_start[
* Right-hand side: [right_start, refs.size()[ */
vector<BVHReference>& refs = *references_;
int left_start = range.start();
int left_end = left_start;
int right_start = range.end();
int right_end = range.end();
BoundBox left_bounds = BoundBox::empty;
BoundBox right_bounds = BoundBox::empty;
for(int i = left_end; i < right_start; i++) {
if(refs[i].bounds().max[this->dim] <= this->pos) {
/* entirely on the left-hand side */
left_bounds.grow(refs[i].bounds());
swap(refs[i], refs[left_end++]);
}
else if(refs[i].bounds().min[this->dim] >= this->pos) {
/* entirely on the right-hand side */
right_bounds.grow(refs[i].bounds());
swap(refs[i--], refs[--right_start]);
}
}
/* Duplicate or unsplit references intersecting both sides.
*
* Duplication happens into a temporary pre-allocated vector in order to
* reduce number of memmove() calls happening in vector.insert().
*/
vector<BVHReference>& new_refs = storage_->new_references;
new_refs.clear();
new_refs.reserve(right_start - left_end);
while(left_end < right_start) {
/* split reference. */
BVHReference lref, rref;
split_reference(*builder, lref, rref, refs[left_end], this->dim, this->pos);
/* compute SAH for duplicate/unsplit candidates. */
BoundBox lub = left_bounds; // Unsplit to left: new left-hand bounds.
BoundBox rub = right_bounds; // Unsplit to right: new right-hand bounds.
BoundBox ldb = left_bounds; // Duplicate: new left-hand bounds.
BoundBox rdb = right_bounds; // Duplicate: new right-hand bounds.
lub.grow(refs[left_end].bounds());
rub.grow(refs[left_end].bounds());
ldb.grow(lref.bounds());
rdb.grow(rref.bounds());
float lac = builder->params.primitive_cost(left_end - left_start);
float rac = builder->params.primitive_cost(right_end - right_start);
float lbc = builder->params.primitive_cost(left_end - left_start + 1);
float rbc = builder->params.primitive_cost(right_end - right_start + 1);
float unsplitLeftSAH = lub.safe_area() * lbc + right_bounds.safe_area() * rac;
float unsplitRightSAH = left_bounds.safe_area() * lac + rub.safe_area() * rbc;
float duplicateSAH = ldb.safe_area() * lbc + rdb.safe_area() * rbc;
float minSAH = min(min(unsplitLeftSAH, unsplitRightSAH), duplicateSAH);
if(minSAH == unsplitLeftSAH) {
/* unsplit to left */
left_bounds = lub;
left_end++;
}
else if(minSAH == unsplitRightSAH) {
/* unsplit to right */
right_bounds = rub;
swap(refs[left_end], refs[--right_start]);
}
else {
/* duplicate */
left_bounds = ldb;
right_bounds = rdb;
refs[left_end++] = lref;
new_refs.push_back(rref);
right_end++;
}
}
/* Insert duplicated references into actual array in one go. */
if(new_refs.size() != 0) {
refs.insert(refs.begin() + (right_end - new_refs.size()),
new_refs.begin(),
new_refs.end());
}
left = BVHRange(left_bounds, left_start, left_end - left_start);
right = BVHRange(right_bounds, right_start, right_end - right_start);
}
BVHSpatialSplit::BVHSpatialSplit(const BVHBuild& builder,
BVHSpatialStorage *storage,
const BVHRange& range,
vector<BVHReference> *references,
float nodeSAH)
: sah(FLT_MAX),
dim(0),
pos(0.0f),
storage_(storage),
references_(references)
{
/* initialize bins. */
float3 origin = range.bounds().min;
float3 binSize = (range.bounds().max - origin) * (1.0f / (float)BVHParams::NUM_SPATIAL_BINS);
float3 invBinSize = 1.0f / binSize;
for(int dim = 0; dim < 3; dim++) {
for(int i = 0; i < BVHParams::NUM_SPATIAL_BINS; i++) {
BVHSpatialBin& bin = storage_->bins[dim][i];
bin.bounds = BoundBox::empty;
bin.enter = 0;
bin.exit = 0;
}
}
/* chop references into bins. */
for(unsigned int refIdx = range.start(); refIdx < range.end(); refIdx++) {
const BVHReference& ref = references_->at(refIdx);
float3 firstBinf = (ref.bounds().min - origin) * invBinSize;
float3 lastBinf = (ref.bounds().max - origin) * invBinSize;
int3 firstBin = make_int3((int)firstBinf.x, (int)firstBinf.y, (int)firstBinf.z);
int3 lastBin = make_int3((int)lastBinf.x, (int)lastBinf.y, (int)lastBinf.z);
firstBin = clamp(firstBin, 0, BVHParams::NUM_SPATIAL_BINS - 1);
lastBin = clamp(lastBin, firstBin, BVHParams::NUM_SPATIAL_BINS - 1);
for(int dim = 0; dim < 3; dim++) {
BVHReference currRef = ref;
for(int i = firstBin[dim]; i < lastBin[dim]; i++) {
BVHReference leftRef, rightRef;
split_reference(builder, leftRef, rightRef, currRef, dim, origin[dim] + binSize[dim] * (float)(i + 1));
storage_->bins[dim][i].bounds.grow(leftRef.bounds());
currRef = rightRef;
}
storage_->bins[dim][lastBin[dim]].bounds.grow(currRef.bounds());
storage_->bins[dim][firstBin[dim]].enter++;
storage_->bins[dim][lastBin[dim]].exit++;
}
}
/* select best split plane. */
for(int dim = 0; dim < 3; dim++) {
/* sweep right to left and determine bounds. */
BoundBox right_bounds = BoundBox::empty;
storage_->right_bounds.resize(BVHParams::NUM_SPATIAL_BINS);
for(int i = BVHParams::NUM_SPATIAL_BINS - 1; i > 0; i--) {
right_bounds.grow(storage_->bins[dim][i].bounds);
storage_->right_bounds[i - 1] = right_bounds;
}
/* sweep left to right and select lowest SAH. */
BoundBox left_bounds = BoundBox::empty;
int leftNum = 0;
int rightNum = range.size();
for(int i = 1; i < BVHParams::NUM_SPATIAL_BINS; i++) {
left_bounds.grow(storage_->bins[dim][i - 1].bounds);
leftNum += storage_->bins[dim][i - 1].enter;
rightNum -= storage_->bins[dim][i - 1].exit;
float sah = nodeSAH +
left_bounds.safe_area() * builder.params.primitive_cost(leftNum) +
storage_->right_bounds[i - 1].safe_area() * builder.params.primitive_cost(rightNum);
if(sah < this->sah) {
this->sah = sah;
this->dim = dim;
this->pos = origin[dim] + binSize[dim] * (float)i;
}
}
}
}