BVHNode* BVHBuild::run()
{
BVHRange root;
/* add references */
add_references(root);
if(progress.get_cancel())
return NULL;
/* init spatial splits */
if(params.top_level) /* todo: get rid of this */
params.use_spatial_split = false;
spatial_min_overlap = root.bounds().safe_area() * params.spatial_split_alpha;
spatial_right_bounds.clear();
spatial_right_bounds.resize(max(root.size(), (int)BVHParams::NUM_SPATIAL_BINS) - 1);
/* init progress updates */
progress_start_time = time_dt();
progress_count = 0;
progress_total = references.size();
progress_original_total = progress_total;
prim_type.resize(references.size());
prim_index.resize(references.size());
prim_object.resize(references.size());
/* build recursively */
BVHNode *rootnode;
if(params.use_spatial_split) {
/* singlethreaded spatial split build */
rootnode = build_node(root, 0);
}
else {
/* multithreaded binning build */
BVHObjectBinning rootbin(root, (references.size())? &references[0]: NULL);
rootnode = build_node(rootbin, 0);
task_pool.wait_work();
}
/* delete if we canceled */
if(rootnode) {
if(progress.get_cancel()) {
rootnode->deleteSubtree();
rootnode = NULL;
}
else if(!params.use_spatial_split) {
/*rotate(rootnode, 4, 5);*/
rootnode->update_visibility();
}
}
return rootnode;
}
BVHNode* BVHBuild::run()
{
BVHRange root;
/* add references */
add_references(root);
if(progress.get_cancel())
return NULL;
/* init spatial splits */
if(params.top_level) {
/* NOTE: Technically it is supported by the builder but it's not really
* optimized for speed yet and not really clear yet if it has measurable
* improvement on render time. Needs some extra investigation before
* enabling spatial split for top level BVH.
*/
params.use_spatial_split = false;
}
spatial_min_overlap = root.bounds().safe_area() * params.spatial_split_alpha;
if(params.use_spatial_split) {
/* NOTE: The API here tries to be as much ready for multi-threaded build
* as possible, but at the same time it tries not to introduce any
* changes in behavior for until all refactoring needed for threading is
* finished.
*
* So we currently allocate single storage for now, which is only used by
* the only thread working on the spatial BVH build.
*/
spatial_storage.resize(TaskScheduler::num_threads() + 1);
size_t num_bins = max(root.size(), (int)BVHParams::NUM_SPATIAL_BINS) - 1;
foreach(BVHSpatialStorage &storage, spatial_storage) {
storage.right_bounds.clear();
}
spatial_storage[0].right_bounds.resize(num_bins);
}
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;
}
}
}
}