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UT_BVHImpl.h
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/*
* Copyright (c) 2018 Side Effects Software Inc.
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*
* COMMENTS:
* Bounding Volume Hierarchy (BVH) implementation.
* The main file is UT_BVH.h; this file is separate so that
* files that don't actually need to call functions on the BVH
* won't have unnecessary headers and functions included.
*/
#pragma once
#ifndef __HDK_UT_BVHImpl_h__
#define __HDK_UT_BVHImpl_h__
#include "UT_BVH.h"
#include "UT_Array.h"
#include "UT_FixedVector.h"
#include "UT_ParallelUtil.h"
#include "UT_SmallArray.h"
#include "SYS_Types.h"
#include <algorithm>
namespace HDK_Sample {
namespace UT {
template<typename T,uint NAXES>
SYS_FORCE_INLINE T utBoxCenter(const UT::Box<T,NAXES>& box, uint axis) noexcept {
const T* v = box.vals[axis];
return v[0] + v[1];
}
template<typename T>
struct ut_BoxCentre {
constexpr static uint scale = 2;
};
template<typename T,uint NAXES,bool INSTANTIATED>
SYS_FORCE_INLINE T utBoxCenter(const UT_FixedVector<T,NAXES,INSTANTIATED>& position, uint axis) noexcept {
return position[axis];
}
template<typename T,uint NAXES,bool INSTANTIATED>
struct ut_BoxCentre<UT_FixedVector<T,NAXES,INSTANTIATED>> {
constexpr static uint scale = 1;
};
template<typename T>
struct ut_BoxCentre<UT_Vector2T<T>> {
constexpr static uint scale = 1;
};
template<typename T>
struct ut_BoxCentre<UT_Vector3T<T>> {
constexpr static uint scale = 1;
};
template<uint N>
template<BVH_Heuristic H,typename T,uint NAXES,typename BOX_TYPE,typename SRC_INT_TYPE>
void BVH<N>::init(const BOX_TYPE* boxes, const INT_TYPE nboxes, SRC_INT_TYPE* indices, bool reorder_indices, INT_TYPE max_items_per_leaf) noexcept {
Box<T,NAXES> axes_minmax;
computeFullBoundingBox(axes_minmax, boxes, nboxes, indices);
init<H>(axes_minmax, boxes, nboxes, indices, reorder_indices, max_items_per_leaf);
}
template<uint N>
template<BVH_Heuristic H,typename T,uint NAXES,typename BOX_TYPE,typename SRC_INT_TYPE>
void BVH<N>::init(const Box<T,NAXES>& axes_minmax, const BOX_TYPE* boxes, const INT_TYPE nboxes, SRC_INT_TYPE* indices, bool reorder_indices, INT_TYPE max_items_per_leaf) noexcept {
// Clear the tree in advance to save memory.
myRoot.reset();
if (nboxes == 0) {
myNumNodes = 0;
return;
}
UT_Array<INT_TYPE> local_indices;
if (!indices) {
local_indices.setSizeNoInit(nboxes);
indices = local_indices.array();
createTrivialIndices(indices, nboxes);
}
UT_Array<Node> nodes;
// Preallocate an overestimate of the number of nodes needed.
nodes.setCapacity(nodeEstimate(nboxes));
nodes.setSize(1);
if (reorder_indices)
initNodeReorder<H>(nodes, nodes[0], axes_minmax, boxes, indices, nboxes, 0, max_items_per_leaf);
else
initNode<H>(nodes, nodes[0], axes_minmax, boxes, indices, nboxes);
// If capacity is more than 12.5% over the size, rellocate.
if (8*nodes.capacity() > 9*nodes.size()) {
nodes.setCapacity(nodes.size());
}
// Steal ownership of the array from the UT_Array
myRoot.reset(nodes.array());
myNumNodes = nodes.size();
nodes.unsafeClearData();
}
template<uint N>
template<typename LOCAL_DATA,typename FUNCTORS>
void BVH<N>::traverse(
FUNCTORS &functors,
LOCAL_DATA* data_for_parent) const noexcept
{
if (!myRoot)
return;
// NOTE: The root is always index 0.
traverseHelper(0, INT_TYPE(-1), functors, data_for_parent);
}
template<uint N>
template<typename LOCAL_DATA,typename FUNCTORS>
void BVH<N>::traverseHelper(
INT_TYPE nodei,
INT_TYPE parent_nodei,
FUNCTORS &functors,
LOCAL_DATA* data_for_parent) const noexcept
{
const Node &node = myRoot[nodei];
bool descend = functors.pre(nodei, data_for_parent);
if (!descend)
return;
LOCAL_DATA local_data[N];
INT_TYPE s;
for (s = 0; s < N; ++s) {
const INT_TYPE node_int = node.child[s];
if (Node::isInternal(node_int)) {
if (node_int == Node::EMPTY) {
// NOTE: Anything after this will be empty too, so we can break.
break;
}
traverseHelper(Node::getInternalNum(node_int), nodei, functors, &local_data[s]);
}
else {
functors.item(node_int, nodei, local_data[s]);
}
}
// NOTE: s is now the number of non-empty entries in this node.
functors.post(nodei, parent_nodei, data_for_parent, s, local_data);
}
template<uint N>
template<typename LOCAL_DATA,typename FUNCTORS>
void BVH<N>::traverseParallel(
INT_TYPE parallel_threshold,
FUNCTORS& functors,
LOCAL_DATA* data_for_parent) const noexcept
{
if (!myRoot)
return;
// NOTE: The root is always index 0.
traverseParallelHelper(0, INT_TYPE(-1), parallel_threshold, myNumNodes, functors, data_for_parent);
}
template<uint N>
template<typename LOCAL_DATA,typename FUNCTORS>
void BVH<N>::traverseParallelHelper(
INT_TYPE nodei,
INT_TYPE parent_nodei,
INT_TYPE parallel_threshold,
INT_TYPE next_node_id,
FUNCTORS& functors,
LOCAL_DATA* data_for_parent) const noexcept
{
const Node &node = myRoot[nodei];
bool descend = functors.pre(nodei, data_for_parent);
if (!descend)
return;
// To determine the number of nodes in a child's subtree, we take the next
// node ID minus the current child's node ID.
INT_TYPE next_nodes[N];
INT_TYPE nnodes[N];
INT_TYPE nchildren = N;
INT_TYPE nparallel = 0;
// s is currently unsigned, so we check s < N for bounds check.
// The s >= 0 check is in case s ever becomes signed, and should be
// automatically removed by the compiler for unsigned s.
for (INT_TYPE s = N-1; (std::is_signed<INT_TYPE>::value ? (s >= 0) : (s < N)); --s) {
const INT_TYPE node_int = node.child[s];
if (node_int == Node::EMPTY) {
--nchildren;
continue;
}
next_nodes[s] = next_node_id;
if (Node::isInternal(node_int)) {
// NOTE: This depends on BVH<N>::initNode appending the child nodes
// in between their content, instead of all at once.
INT_TYPE child_node_id = Node::getInternalNum(node_int);
nnodes[s] = next_node_id - child_node_id;
next_node_id = child_node_id;
}
else {
nnodes[s] = 0;
}
nparallel += (nnodes[s] >= parallel_threshold);
}
LOCAL_DATA local_data[N];
if (nparallel >= 2) {
// Do any non-parallel ones first
if (nparallel < nchildren) {
for (INT_TYPE s = 0; s < N; ++s) {
if (nnodes[s] >= parallel_threshold) {
continue;
}
const INT_TYPE node_int = node.child[s];
if (Node::isInternal(node_int)) {
if (node_int == Node::EMPTY) {
// NOTE: Anything after this will be empty too, so we can break.
break;
}
traverseHelper(Node::getInternalNum(node_int), nodei, functors, &local_data[s]);
}
else {
functors.item(node_int, nodei, local_data[s]);
}
}
}
// Now do the parallel ones
UTparallelFor(UT_BlockedRange<INT_TYPE>(0,nparallel), [this,nodei,&node,&nnodes,&next_nodes,¶llel_threshold,&functors,&local_data](const UT_BlockedRange<INT_TYPE>& r) {
for (INT_TYPE taski = r.begin(); taski < r.end(); ++taski) {
INT_TYPE parallel_count = 0;
// NOTE: The check for s < N is just so that the compiler can
// (hopefully) figure out that it can fully unroll the loop.
INT_TYPE s;
for (s = 0; s < N; ++s) {
if (nnodes[s] < parallel_threshold) {
continue;
}
if (parallel_count == taski) {
break;
}
++parallel_count;
}
const INT_TYPE node_int = node.child[s];
if (Node::isInternal(node_int)) {
UT_ASSERT_MSG_P(node_int != Node::EMPTY, "Empty entries should have been excluded above.");
traverseParallelHelper(Node::getInternalNum(node_int), nodei, parallel_threshold, next_nodes[s], functors, &local_data[s]);
}
else {
functors.item(node_int, nodei, local_data[s]);
}
}
}, 0, 1);
}
else {
// All in serial
for (INT_TYPE s = 0; s < N; ++s) {
const INT_TYPE node_int = node.child[s];
if (Node::isInternal(node_int)) {
if (node_int == Node::EMPTY) {
// NOTE: Anything after this will be empty too, so we can break.
break;
}
traverseHelper(Node::getInternalNum(node_int), nodei, functors, &local_data[s]);
}
else {
functors.item(node_int, nodei, local_data[s]);
}
}
}
functors.post(nodei, parent_nodei, data_for_parent, nchildren, local_data);
}
template<uint N>
template<typename LOCAL_DATA,typename FUNCTORS>
void BVH<N>::traverseVector(
FUNCTORS &functors,
LOCAL_DATA* data_for_parent) const noexcept
{
if (!myRoot)
return;
// NOTE: The root is always index 0.
traverseVectorHelper(0, INT_TYPE(-1), functors, data_for_parent);
}
template<uint N>
template<typename LOCAL_DATA,typename FUNCTORS>
void BVH<N>::traverseVectorHelper(
INT_TYPE nodei,
INT_TYPE parent_nodei,
FUNCTORS &functors,
LOCAL_DATA* data_for_parent) const noexcept
{
const Node &node = myRoot[nodei];
INT_TYPE descend = functors.pre(nodei, data_for_parent);
if (!descend)
return;
LOCAL_DATA local_data[N];
INT_TYPE s;
for (s = 0; s < N; ++s) {
if ((descend>>s) & 1) {
const INT_TYPE node_int = node.child[s];
if (Node::isInternal(node_int)) {
if (node_int == Node::EMPTY) {
// NOTE: Anything after this will be empty too, so we can break.
descend &= (INT_TYPE(1)<<s)-1;
break;
}
traverseVectorHelper(Node::getInternalNum(node_int), nodei, functors, &local_data[s]);
}
else {
functors.item(node_int, nodei, local_data[s]);
}
}
}
// NOTE: s is now the number of non-empty entries in this node.
functors.post(nodei, parent_nodei, data_for_parent, s, local_data, descend);
}
template<uint N>
template<typename SRC_INT_TYPE>
void BVH<N>::createTrivialIndices(SRC_INT_TYPE* indices, const INT_TYPE n) noexcept {
constexpr INT_TYPE PARALLEL_THRESHOLD = 65536;
INT_TYPE ntasks = 1;
if (n >= PARALLEL_THRESHOLD) {
INT_TYPE nprocessors = UT_Thread::getNumProcessors();
ntasks = (nprocessors > 1) ? SYSmin(4*nprocessors, n/(PARALLEL_THRESHOLD/2)) : 1;
}
if (ntasks == 1) {
for (INT_TYPE i = 0; i < n; ++i) {
indices[i] = i;
}
}
else {
UTparallelFor(UT_BlockedRange<INT_TYPE>(0,n), [indices](const UT_BlockedRange<INT_TYPE>& r) {
for (INT_TYPE i = r.begin(), end = r.end(); i != end; ++i) {
indices[i] = i;
}
}, 0, 1);
}
}
template<uint N>
template<typename T,uint NAXES,typename BOX_TYPE,typename SRC_INT_TYPE>
void BVH<N>::computeFullBoundingBox(Box<T,NAXES>& axes_minmax, const BOX_TYPE* boxes, const INT_TYPE nboxes, SRC_INT_TYPE* indices) noexcept {
if (!nboxes) {
axes_minmax.initBounds();
return;
}
INT_TYPE ntasks = 1;
if (nboxes >= 2*4096) {
INT_TYPE nprocessors = UT_Thread::getNumProcessors();
ntasks = (nprocessors > 1) ? SYSmin(4*nprocessors, nboxes/4096) : 1;
}
if (ntasks == 1) {
Box<T,NAXES> box;
if (indices) {
box.initBounds(boxes[indices[0]]);
for (INT_TYPE i = 1; i < nboxes; ++i) {
box.combine(boxes[indices[i]]);
}
}
else {
box.initBounds(boxes[0]);
for (INT_TYPE i = 1; i < nboxes; ++i) {
box.combine(boxes[i]);
}
}
axes_minmax = box;
}
else {
// Combine boxes in parallel, into just a few boxes
UT_SmallArray<Box<T,NAXES>> parallel_boxes;
parallel_boxes.setSize(ntasks);
UTparallelFor(UT_BlockedRange<INT_TYPE>(0,ntasks), [¶llel_boxes,ntasks,boxes,nboxes,indices](const UT_BlockedRange<INT_TYPE>& r) {
for (INT_TYPE taski = r.begin(), end = r.end(); taski < end; ++taski) {
const INT_TYPE startbox = (taski*uint64(nboxes))/ntasks;
const INT_TYPE endbox = ((taski+1)*uint64(nboxes))/ntasks;
Box<T,NAXES> box;
if (indices) {
box.initBounds(boxes[indices[startbox]]);
for (INT_TYPE i = startbox+1; i < endbox; ++i) {
box.combine(boxes[indices[i]]);
}
}
else {
box.initBounds(boxes[startbox]);
for (INT_TYPE i = startbox+1; i < endbox; ++i) {
box.combine(boxes[i]);
}
}
parallel_boxes[taski] = box;
}
}, 0, 1);
// Combine parallel_boxes
Box<T,NAXES> box = parallel_boxes[0];
for (INT_TYPE i = 1; i < ntasks; ++i) {
box.combine(parallel_boxes[i]);
}
axes_minmax = box;
}
}
template<uint N>
template<BVH_Heuristic H,typename T,uint NAXES,typename BOX_TYPE,typename SRC_INT_TYPE>
void BVH<N>::initNode(UT_Array<Node>& nodes, Node &node, const Box<T,NAXES>& axes_minmax, const BOX_TYPE* boxes, SRC_INT_TYPE* indices, INT_TYPE nboxes) noexcept {
if (nboxes <= N) {
// Fits in one node
for (INT_TYPE i = 0; i < nboxes; ++i) {
node.child[i] = indices[i];
}
for (INT_TYPE i = nboxes; i < N; ++i) {
node.child[i] = Node::EMPTY;
}
return;
}
SRC_INT_TYPE* sub_indices[N+1];
Box<T,NAXES> sub_boxes[N];
if (N == 2) {
sub_indices[0] = indices;
sub_indices[2] = indices+nboxes;
split<H>(axes_minmax, boxes, indices, nboxes, sub_indices[1], &sub_boxes[0]);
}
else {
multiSplit<H>(axes_minmax, boxes, indices, nboxes, sub_indices, sub_boxes);
}
// Count the number of nodes to run in parallel and fill in single items in this node
INT_TYPE nparallel = 0;
static constexpr INT_TYPE PARALLEL_THRESHOLD = 1024;
for (INT_TYPE i = 0; i < N; ++i) {
INT_TYPE sub_nboxes = sub_indices[i+1]-sub_indices[i];
if (sub_nboxes == 1) {
node.child[i] = sub_indices[i][0];
}
else if (sub_nboxes >= PARALLEL_THRESHOLD) {
++nparallel;
}
}
// NOTE: Child nodes of this node need to be placed just before the nodes in
// their corresponding subtree, in between the subtrees, because
// traverseParallel uses the difference between the child node IDs
// to determine the number of nodes in the subtree.
// Recurse
if (nparallel >= 2) {
// Do the parallel ones first, so that they can be inserted in the right place.
// Although the choice may seem somewhat arbitrary, we need the results to be
// identical whether we choose to parallelize or not, and in case we change the
// threshold later.
UT_SmallArray<UT_Array<Node>> parallel_nodes;
parallel_nodes.setSize(nparallel);
UT_SmallArray<Node> parallel_parent_nodes;
parallel_parent_nodes.setSize(nparallel);
UTparallelFor(UT_BlockedRange<INT_TYPE>(0,nparallel), [¶llel_nodes,¶llel_parent_nodes,&sub_indices,boxes,&sub_boxes](const UT_BlockedRange<INT_TYPE>& r) {
for (INT_TYPE taski = r.begin(), end = r.end(); taski < end; ++taski) {
// First, find which child this is
INT_TYPE counted_parallel = 0;
INT_TYPE sub_nboxes;
INT_TYPE childi;
for (childi = 0; childi < N; ++childi) {
sub_nboxes = sub_indices[childi+1]-sub_indices[childi];
if (sub_nboxes >= PARALLEL_THRESHOLD) {
if (counted_parallel == taski) {
break;
}
++counted_parallel;
}
}
UT_ASSERT_P(counted_parallel == taski);
UT_Array<Node>& local_nodes = parallel_nodes[taski];
// Preallocate an overestimate of the number of nodes needed.
// At worst, we could have only 2 children in every leaf, and
// then above that, we have a geometric series with r=1/N and a=(sub_nboxes/2)/N
// The true worst case might be a little worst than this, but
// it's probably fairly unlikely.
local_nodes.setCapacity(nodeEstimate(sub_nboxes));
Node& parent_node = parallel_parent_nodes[taski];
// We'll have to fix the internal node numbers in parent_node and local_nodes later
initNode<H>(local_nodes, parent_node, sub_boxes[childi], boxes, sub_indices[childi], sub_nboxes);
}
}, 0, 1);
INT_TYPE counted_parallel = 0;
for (INT_TYPE i = 0; i < N; ++i) {
INT_TYPE sub_nboxes = sub_indices[i+1]-sub_indices[i];
if (sub_nboxes != 1) {
INT_TYPE local_nodes_start = nodes.size();
node.child[i] = Node::markInternal(local_nodes_start);
if (sub_nboxes >= PARALLEL_THRESHOLD) {
// First, adjust the root child node
Node child_node = parallel_parent_nodes[counted_parallel];
++local_nodes_start;
for (INT_TYPE childi = 0; childi < N; ++childi) {
INT_TYPE child_child = child_node.child[childi];
if (Node::isInternal(child_child) && child_child != Node::EMPTY) {
child_child += local_nodes_start;
child_node.child[childi] = child_child;
}
}
// Make space in the array for the sub-child nodes
const UT_Array<Node>& local_nodes = parallel_nodes[counted_parallel];
++counted_parallel;
INT_TYPE n = local_nodes.size();
nodes.bumpSize(local_nodes_start + n);
nodes[local_nodes_start-1] = child_node;
}
else {
nodes.bumpSize(local_nodes_start + 1);
initNode<H>(nodes, nodes[local_nodes_start], sub_boxes[i], boxes, sub_indices[i], sub_nboxes);
}
}
}
// Now, adjust and copy all sub-child nodes that were made in parallel
adjustParallelChildNodes<PARALLEL_THRESHOLD>(nparallel, nodes, node, parallel_nodes.array(), sub_indices);
}
else {
for (INT_TYPE i = 0; i < N; ++i) {
INT_TYPE sub_nboxes = sub_indices[i+1]-sub_indices[i];
if (sub_nboxes != 1) {
INT_TYPE local_nodes_start = nodes.size();
node.child[i] = Node::markInternal(local_nodes_start);
nodes.bumpSize(local_nodes_start + 1);
initNode<H>(nodes, nodes[local_nodes_start], sub_boxes[i], boxes, sub_indices[i], sub_nboxes);
}
}
}
}
template<uint N>
template<BVH_Heuristic H,typename T,uint NAXES,typename BOX_TYPE,typename SRC_INT_TYPE>
void BVH<N>::initNodeReorder(UT_Array<Node>& nodes, Node &node, const Box<T,NAXES>& axes_minmax, const BOX_TYPE* boxes, SRC_INT_TYPE* indices, INT_TYPE nboxes, const INT_TYPE indices_offset, const INT_TYPE max_items_per_leaf) noexcept {
if (nboxes <= N) {
// Fits in one node
for (INT_TYPE i = 0; i < nboxes; ++i) {
node.child[i] = indices_offset+i;
}
for (INT_TYPE i = nboxes; i < N; ++i) {
node.child[i] = Node::EMPTY;
}
return;
}
SRC_INT_TYPE* sub_indices[N+1];
Box<T,NAXES> sub_boxes[N];
if (N == 2) {
sub_indices[0] = indices;
sub_indices[2] = indices+nboxes;
split<H>(axes_minmax, boxes, indices, nboxes, sub_indices[1], &sub_boxes[0]);
}
else {
multiSplit<H>(axes_minmax, boxes, indices, nboxes, sub_indices, sub_boxes);
}
// Move any children with max_items_per_leaf or fewer indices before any children with more,
// for better cache coherence when we're accessing data in a corresponding array.
INT_TYPE nleaves = 0;
UT_SmallArray<SRC_INT_TYPE> leaf_indices;
SRC_INT_TYPE leaf_sizes[N];
INT_TYPE sub_nboxes0 = sub_indices[1]-sub_indices[0];
if (sub_nboxes0 <= max_items_per_leaf) {
leaf_sizes[0] = sub_nboxes0;
for (int j = 0; j < sub_nboxes0; ++j)
leaf_indices.append(sub_indices[0][j]);
++nleaves;
}
INT_TYPE sub_nboxes1 = sub_indices[2]-sub_indices[1];
if (sub_nboxes1 <= max_items_per_leaf) {
leaf_sizes[nleaves] = sub_nboxes1;
for (int j = 0; j < sub_nboxes1; ++j)
leaf_indices.append(sub_indices[1][j]);
++nleaves;
}
for (INT_TYPE i = 2; i < N; ++i) {
INT_TYPE sub_nboxes = sub_indices[i+1]-sub_indices[i];
if (sub_nboxes <= max_items_per_leaf) {
leaf_sizes[nleaves] = sub_nboxes;
for (int j = 0; j < sub_nboxes; ++j)
leaf_indices.append(sub_indices[i][j]);
++nleaves;
}
}
if (nleaves > 0) {
// NOTE: i < N condition is because INT_TYPE is unsigned.
// i >= 0 condition is in case INT_TYPE is changed to signed.
INT_TYPE move_distance = 0;
INT_TYPE index_move_distance = 0;
for (INT_TYPE i = N-1; (std::is_signed<INT_TYPE>::value ? (i >= 0) : (i < N)); --i) {
INT_TYPE sub_nboxes = sub_indices[i+1]-sub_indices[i];
if (sub_nboxes <= max_items_per_leaf) {
++move_distance;
index_move_distance += sub_nboxes;
}
else if (move_distance > 0) {
SRC_INT_TYPE *start_src_index = sub_indices[i];
for (SRC_INT_TYPE *src_index = sub_indices[i+1]-1; src_index >= start_src_index; --src_index) {
src_index[index_move_distance] = src_index[0];
}
sub_indices[i+move_distance] = sub_indices[i]+index_move_distance;
}
}
index_move_distance = 0;
for (INT_TYPE i = 0; i < nleaves; ++i) {
INT_TYPE sub_nboxes = leaf_sizes[i];
sub_indices[i] = indices+index_move_distance;
for (int j = 0; j < sub_nboxes; ++j)
indices[index_move_distance+j] = leaf_indices[index_move_distance+j];
index_move_distance += sub_nboxes;
}
}
// Count the number of nodes to run in parallel and fill in single items in this node
INT_TYPE nparallel = 0;
static constexpr INT_TYPE PARALLEL_THRESHOLD = 1024;
for (INT_TYPE i = 0; i < N; ++i) {
INT_TYPE sub_nboxes = sub_indices[i+1]-sub_indices[i];
if (sub_nboxes <= max_items_per_leaf) {
node.child[i] = indices_offset+(sub_indices[i]-sub_indices[0]);
}
else if (sub_nboxes >= PARALLEL_THRESHOLD) {
++nparallel;
}
}
// NOTE: Child nodes of this node need to be placed just before the nodes in
// their corresponding subtree, in between the subtrees, because
// traverseParallel uses the difference between the child node IDs
// to determine the number of nodes in the subtree.
// Recurse
if (nparallel >= 2) {
// Do the parallel ones first, so that they can be inserted in the right place.
// Although the choice may seem somewhat arbitrary, we need the results to be
// identical whether we choose to parallelize or not, and in case we change the
// threshold later.
UT_SmallArray<UT_Array<Node>,4*sizeof(UT_Array<Node>)> parallel_nodes;
parallel_nodes.setSize(nparallel);
UT_SmallArray<Node,4*sizeof(Node)> parallel_parent_nodes;
parallel_parent_nodes.setSize(nparallel);
UTparallelFor(UT_BlockedRange<INT_TYPE>(0,nparallel), [¶llel_nodes,¶llel_parent_nodes,&sub_indices,boxes,&sub_boxes,indices_offset,max_items_per_leaf](const UT_BlockedRange<INT_TYPE>& r) {
for (INT_TYPE taski = r.begin(), end = r.end(); taski < end; ++taski) {
// First, find which child this is
INT_TYPE counted_parallel = 0;
INT_TYPE sub_nboxes;
INT_TYPE childi;
for (childi = 0; childi < N; ++childi) {
sub_nboxes = sub_indices[childi+1]-sub_indices[childi];
if (sub_nboxes >= PARALLEL_THRESHOLD) {
if (counted_parallel == taski) {
break;
}
++counted_parallel;
}
}
UT_ASSERT_P(counted_parallel == taski);
UT_Array<Node>& local_nodes = parallel_nodes[taski];
// Preallocate an overestimate of the number of nodes needed.
// At worst, we could have only 2 children in every leaf, and
// then above that, we have a geometric series with r=1/N and a=(sub_nboxes/2)/N
// The true worst case might be a little worst than this, but
// it's probably fairly unlikely.
local_nodes.setCapacity(nodeEstimate(sub_nboxes));
Node& parent_node = parallel_parent_nodes[taski];
// We'll have to fix the internal node numbers in parent_node and local_nodes later
initNodeReorder<H>(local_nodes, parent_node, sub_boxes[childi], boxes, sub_indices[childi], sub_nboxes,
indices_offset+(sub_indices[childi]-sub_indices[0]), max_items_per_leaf);
}
}, 0, 1);
INT_TYPE counted_parallel = 0;
for (INT_TYPE i = 0; i < N; ++i) {
INT_TYPE sub_nboxes = sub_indices[i+1]-sub_indices[i];
if (sub_nboxes > max_items_per_leaf) {
INT_TYPE local_nodes_start = nodes.size();
node.child[i] = Node::markInternal(local_nodes_start);
if (sub_nboxes >= PARALLEL_THRESHOLD) {
// First, adjust the root child node
Node child_node = parallel_parent_nodes[counted_parallel];
++local_nodes_start;
for (INT_TYPE childi = 0; childi < N; ++childi) {
INT_TYPE child_child = child_node.child[childi];
if (Node::isInternal(child_child) && child_child != Node::EMPTY) {
child_child += local_nodes_start;
child_node.child[childi] = child_child;
}
}
// Make space in the array for the sub-child nodes
const UT_Array<Node>& local_nodes = parallel_nodes[counted_parallel];
++counted_parallel;
INT_TYPE n = local_nodes.size();
nodes.bumpSize(local_nodes_start + n);
nodes[local_nodes_start-1] = child_node;
}
else {
nodes.bumpSize(local_nodes_start + 1);
initNodeReorder<H>(nodes, nodes[local_nodes_start], sub_boxes[i], boxes, sub_indices[i], sub_nboxes,
indices_offset+(sub_indices[i]-sub_indices[0]), max_items_per_leaf);
}
}
}
// Now, adjust and copy all sub-child nodes that were made in parallel
adjustParallelChildNodes<PARALLEL_THRESHOLD>(nparallel, nodes, node, parallel_nodes.array(), sub_indices);
}
else {
for (INT_TYPE i = 0; i < N; ++i) {
INT_TYPE sub_nboxes = sub_indices[i+1]-sub_indices[i];
if (sub_nboxes > max_items_per_leaf) {
INT_TYPE local_nodes_start = nodes.size();
node.child[i] = Node::markInternal(local_nodes_start);
nodes.bumpSize(local_nodes_start + 1);
initNodeReorder<H>(nodes, nodes[local_nodes_start], sub_boxes[i], boxes, sub_indices[i], sub_nboxes,
indices_offset+(sub_indices[i]-sub_indices[0]), max_items_per_leaf);
}
}
}
}
template<uint N>
template<BVH_Heuristic H,typename T,uint NAXES,typename BOX_TYPE,typename SRC_INT_TYPE>
void BVH<N>::multiSplit(const Box<T,NAXES>& axes_minmax, const BOX_TYPE* boxes, SRC_INT_TYPE* indices, INT_TYPE nboxes, SRC_INT_TYPE* sub_indices[N+1], Box<T,NAXES> sub_boxes[N]) noexcept {
sub_indices[0] = indices;
sub_indices[2] = indices+nboxes;
split<H>(axes_minmax, boxes, indices, nboxes, sub_indices[1], &sub_boxes[0]);
if (N == 2) {
return;
}
if (H == BVH_Heuristic::MEDIAN_MAX_AXIS) {
SRC_INT_TYPE* sub_indices_startend[2*N];
Box<T,NAXES> sub_boxes_unsorted[N];
sub_boxes_unsorted[0] = sub_boxes[0];
sub_boxes_unsorted[1] = sub_boxes[1];
sub_indices_startend[0] = sub_indices[0];
sub_indices_startend[1] = sub_indices[1];
sub_indices_startend[2] = sub_indices[1];
sub_indices_startend[3] = sub_indices[2];
for (INT_TYPE nsub = 2; nsub < N; ++nsub) {
SRC_INT_TYPE* selected_start = sub_indices_startend[0];
SRC_INT_TYPE* selected_end = sub_indices_startend[1];
Box<T,NAXES> sub_box = sub_boxes_unsorted[0];
// Shift results back.
for (INT_TYPE i = 0; i < nsub-1; ++i) {
sub_indices_startend[2*i ] = sub_indices_startend[2*i+2];
sub_indices_startend[2*i+1] = sub_indices_startend[2*i+3];
}
for (INT_TYPE i = 0; i < nsub-1; ++i) {
sub_boxes_unsorted[i] = sub_boxes_unsorted[i-1];
}
// Do the split
split<H>(sub_box, boxes, selected_start, selected_end-selected_start, sub_indices_startend[2*nsub-1], &sub_boxes_unsorted[nsub]);
sub_indices_startend[2*nsub-2] = selected_start;
sub_indices_startend[2*nsub] = sub_indices_startend[2*nsub-1];
sub_indices_startend[2*nsub+1] = selected_end;
// Sort pointers so that they're in the correct order
sub_indices[N] = indices+nboxes;
for (INT_TYPE i = 0; i < N; ++i) {
SRC_INT_TYPE* prev_pointer = (i != 0) ? sub_indices[i-1] : nullptr;
SRC_INT_TYPE* min_pointer = nullptr;
Box<T,NAXES> box;
for (INT_TYPE j = 0; j < N; ++j) {
SRC_INT_TYPE* cur_pointer = sub_indices_startend[2*j];
if ((cur_pointer > prev_pointer) && (!min_pointer || (cur_pointer < min_pointer))) {
min_pointer = cur_pointer;
box = sub_boxes_unsorted[j];
}
}
UT_ASSERT_P(min_pointer);
sub_indices[i] = min_pointer;
sub_boxes[i] = box;
}
}
}
else {
T sub_box_areas[N];
sub_box_areas[0] = unweightedHeuristic<H>(sub_boxes[0]);
sub_box_areas[1] = unweightedHeuristic<H>(sub_boxes[1]);
for (INT_TYPE nsub = 2; nsub < N; ++nsub) {
// Choose which one to split
INT_TYPE split_choice = INT_TYPE(-1);
T max_heuristic;
for (INT_TYPE i = 0; i < nsub; ++i) {
const INT_TYPE index_count = (sub_indices[i+1]-sub_indices[i]);
if (index_count > 1) {
const T heuristic = sub_box_areas[i]*index_count;
if (split_choice == INT_TYPE(-1) || heuristic > max_heuristic) {
split_choice = i;
max_heuristic = heuristic;
}
}
}
UT_ASSERT_MSG_P(split_choice != INT_TYPE(-1), "There should always be at least one that can be split!");
SRC_INT_TYPE* selected_start = sub_indices[split_choice];
SRC_INT_TYPE* selected_end = sub_indices[split_choice+1];
// Shift results over; we can skip the one we selected.
for (INT_TYPE i = nsub; i > split_choice; --i) {
sub_indices[i+1] = sub_indices[i];
}
for (INT_TYPE i = nsub-1; i > split_choice; --i) {
sub_boxes[i+1] = sub_boxes[i];
}
for (INT_TYPE i = nsub-1; i > split_choice; --i) {
sub_box_areas[i+1] = sub_box_areas[i];
}
// Do the split
split<H>(sub_boxes[split_choice], boxes, selected_start, selected_end-selected_start, sub_indices[split_choice+1], &sub_boxes[split_choice]);
sub_box_areas[split_choice] = unweightedHeuristic<H>(sub_boxes[split_choice]);
sub_box_areas[split_choice+1] = unweightedHeuristic<H>(sub_boxes[split_choice+1]);
}
}
}
template<uint N>
template<BVH_Heuristic H,typename T,uint NAXES,typename BOX_TYPE,typename SRC_INT_TYPE>
void BVH<N>::split(const Box<T,NAXES>& axes_minmax, const BOX_TYPE* boxes, SRC_INT_TYPE* indices, INT_TYPE nboxes, SRC_INT_TYPE*& split_indices, Box<T,NAXES>* split_boxes) noexcept {
if (nboxes == 2) {
split_boxes[0].initBounds(boxes[indices[0]]);
split_boxes[1].initBounds(boxes[indices[1]]);
split_indices = indices+1;
return;
}
UT_ASSERT_MSG_P(nboxes > 2, "Cases with less than 3 boxes should have already been handled!");
if (H == BVH_Heuristic::MEDIAN_MAX_AXIS) {
UT_ASSERT_MSG(0, "FIXME: Implement this!!!");
}
constexpr INT_TYPE SMALL_LIMIT = 6;
if (nboxes <= SMALL_LIMIT) {
// Special case for a small number of boxes: check all (2^(n-1))-1 partitions.
// Without loss of generality, we assume that box 0 is in partition 0,
// and that not all boxes are in partition 0.
Box<T,NAXES> local_boxes[SMALL_LIMIT];
for (INT_TYPE box = 0; box < nboxes; ++box) {
local_boxes[box].initBounds(boxes[indices[box]]);
//printf("Box %u: (%f-%f)x(%f-%f)x(%f-%f)\n", uint(box), local_boxes[box].vals[0][0], local_boxes[box].vals[0][1], local_boxes[box].vals[1][0], local_boxes[box].vals[1][1], local_boxes[box].vals[2][0], local_boxes[box].vals[2][1]);
}
const INT_TYPE partition_limit = (INT_TYPE(1)<<(nboxes-1));
INT_TYPE best_partition = INT_TYPE(-1);
T best_heuristic;
for (INT_TYPE partition_bits = 1; partition_bits < partition_limit; ++partition_bits) {
Box<T,NAXES> sub_boxes[2];
sub_boxes[0] = local_boxes[0];
sub_boxes[1].initBounds();
INT_TYPE sub_counts[2] = {1,0};
for (INT_TYPE bit = 0; bit < nboxes-1; ++bit) {
INT_TYPE dest = (partition_bits>>bit)&1;
sub_boxes[dest].combine(local_boxes[bit+1]);
++sub_counts[dest];
}
//printf("Partition bits %u: sub_box[0]: (%f-%f)x(%f-%f)x(%f-%f)\n", uint(partition_bits), sub_boxes[0].vals[0][0], sub_boxes[0].vals[0][1], sub_boxes[0].vals[1][0], sub_boxes[0].vals[1][1], sub_boxes[0].vals[2][0], sub_boxes[0].vals[2][1]);
//printf("Partition bits %u: sub_box[1]: (%f-%f)x(%f-%f)x(%f-%f)\n", uint(partition_bits), sub_boxes[1].vals[0][0], sub_boxes[1].vals[0][1], sub_boxes[1].vals[1][0], sub_boxes[1].vals[1][1], sub_boxes[1].vals[2][0], sub_boxes[1].vals[2][1]);
const T heuristic =
unweightedHeuristic<H>(sub_boxes[0])*sub_counts[0] +
unweightedHeuristic<H>(sub_boxes[1])*sub_counts[1];
//printf("Partition bits %u: heuristic = %f (= %f*%u + %f*%u)\n",uint(partition_bits),heuristic, unweightedHeuristic<H>(sub_boxes[0]), uint(sub_counts[0]), unweightedHeuristic<H>(sub_boxes[1]), uint(sub_counts[1]));
if (best_partition == INT_TYPE(-1) || heuristic < best_heuristic) {
//printf(" New best\n");
best_partition = partition_bits;
best_heuristic = heuristic;
split_boxes[0] = sub_boxes[0];
split_boxes[1] = sub_boxes[1];
}
}
#if 0 // This isn't actually necessary with the current design, because I changed how the number of subtree nodes is determined.
// If best_partition is partition_limit-1, there's only 1 box
// in partition 0. We should instead put this in partition 1,
// so that we can help always have the internal node indices first
// in each node. That gets used to (fairly) quickly determine
// the number of nodes in a sub-tree.
if (best_partition == partition_limit - 1) {
// Put the first index last.
SRC_INT_TYPE last_index = indices[0];
SRC_INT_TYPE* dest_indices = indices;
SRC_INT_TYPE* local_split_indices = indices + nboxes-1;
for (; dest_indices != local_split_indices; ++dest_indices) {
dest_indices[0] = dest_indices[1];
}
*local_split_indices = last_index;
split_indices = local_split_indices;
// Swap the boxes
const Box<T,NAXES> temp_box = sub_boxes[0];
sub_boxes[0] = sub_boxes[1];
sub_boxes[1] = temp_box;
return;
}
#endif
// Reorder the indices.
// NOTE: Index 0 is always in partition 0, so can stay put.
SRC_INT_TYPE local_indices[SMALL_LIMIT-1];
for (INT_TYPE box = 0; box < nboxes-1; ++box) {
local_indices[box] = indices[box+1];
}
SRC_INT_TYPE* dest_indices = indices+1;
SRC_INT_TYPE* src_indices = local_indices;
// Copy partition 0
for (INT_TYPE bit = 0; bit < nboxes-1; ++bit, ++src_indices) {
if (!((best_partition>>bit)&1)) {
//printf("Copying %u into partition 0\n",uint(*src_indices));
*dest_indices = *src_indices;
++dest_indices;
}
}
split_indices = dest_indices;
// Copy partition 1
src_indices = local_indices;
for (INT_TYPE bit = 0; bit < nboxes-1; ++bit, ++src_indices) {
if ((best_partition>>bit)&1) {
//printf("Copying %u into partition 1\n",uint(*src_indices));
*dest_indices = *src_indices;
++dest_indices;
}
}
return;
}
uint max_axis = 0;
T max_axis_length = axes_minmax.vals[0][1] - axes_minmax.vals[0][0];
for (uint axis = 1; axis < NAXES; ++axis) {
const T axis_length = axes_minmax.vals[axis][1] - axes_minmax.vals[axis][0];
if (axis_length > max_axis_length) {
max_axis = axis;
max_axis_length = axis_length;
}
}
if (!(max_axis_length > T(0))) {
// All boxes are a single point or NaN.
// Pick an arbitrary split point.
split_indices = indices + nboxes/2;
split_boxes[0] = axes_minmax;
split_boxes[1] = axes_minmax;
return;
}
const INT_TYPE axis = max_axis;
constexpr INT_TYPE MID_LIMIT = 2*NSPANS;
if (nboxes <= MID_LIMIT) {
// Sort along axis, and try all possible splits.
#if 1
// First, compute midpoints
T midpointsx2[MID_LIMIT];
for (INT_TYPE i = 0; i < nboxes; ++i) {
midpointsx2[i] = utBoxCenter(boxes[indices[i]], axis);
}
SRC_INT_TYPE local_indices[MID_LIMIT];
for (INT_TYPE i = 0; i < nboxes; ++i) {
local_indices[i] = i;
}
const INT_TYPE chunk_starts[5] = {0, nboxes/4, nboxes/2, INT_TYPE((3*uint64(nboxes))/4), nboxes};
// For sorting, insertion sort 4 chunks and merge them
for (INT_TYPE chunk = 0; chunk < 4; ++chunk) {
const INT_TYPE start = chunk_starts[chunk];
const INT_TYPE end = chunk_starts[chunk+1];
for (INT_TYPE i = start+1; i < end; ++i) {
SRC_INT_TYPE indexi = local_indices[i];
T vi = midpointsx2[indexi];
for (INT_TYPE j = start; j < i; ++j) {
SRC_INT_TYPE indexj = local_indices[j];
T vj = midpointsx2[indexj];
if (vi < vj) {
do {
local_indices[j] = indexi;