BAH::BAHNode *BAH::recursiveBuild(std::vector<BAHElement> &buildData,
uint32_t start, uint32_t end,
uint32_t *totalNodes,
std::vector<uint32_t> &orderedElements) {
(*totalNodes)++;
BAHNode *node = new BAHNode();
ponos::bbox2 bbox;
for (uint32_t i = start; i < end; ++i)
bbox = ponos::make_union(bbox, buildData[i].bounds);
// compute all bounds
uint32_t nElements = end - start;
if (nElements == 1) {
// create leaf node
uint32_t firstElementOffset = orderedElements.size();
for (uint32_t i = start; i < end; i++) {
uint32_t elementNum = buildData[i].ind;
orderedElements.emplace_back(elementNum);
}
node->initLeaf(firstElementOffset, nElements, bbox);
} else {
// compute bound of primitives
ponos::bbox2 centroidBounds;
for (uint32_t i = start; i < end; i++)
centroidBounds = ponos::make_union(centroidBounds, buildData[i].centroid);
int dim = centroidBounds.maxExtent();
// partition primitives
uint32_t mid = (start + end) / 2;
if (centroidBounds.upper[dim] == centroidBounds.lower[dim]) {
node->initInterior(
dim,
recursiveBuild(buildData, start, mid, totalNodes, orderedElements),
recursiveBuild(buildData, mid, end, totalNodes, orderedElements));
return node;
}
// partition into equally sized subsets
std::nth_element(&buildData[start], &buildData[mid],
&buildData[end - 1] + 1, ComparePoints(dim));
node->initInterior(
dim, recursiveBuild(buildData, start, mid, totalNodes, orderedElements),
recursiveBuild(buildData, mid, end, totalNodes, orderedElements));
}
return node;
}
BVHBuildNode *CBVH_PBRT::recursiveBuild ( std::vector<BVHPrimitiveInfo> &primitiveInfo,
int start,
int end,
int *totalNodes,
CONST_VECTOR_OBJECT &orderedPrims )
{
wxASSERT( totalNodes != NULL );
wxASSERT( start >= 0 );
wxASSERT( end >= 0 );
wxASSERT( start != end );
wxASSERT( start < end );
wxASSERT( start <= (int)primitiveInfo.size() );
wxASSERT( end <= (int)primitiveInfo.size() );
(*totalNodes)++;
// !TODO: implement an memory Arena
BVHBuildNode *node = static_cast<BVHBuildNode *>( _mm_malloc( sizeof( BVHBuildNode ),
L1_CACHE_LINE_SIZE ) );
m_addresses_pointer_to_mm_free.push_back( node );
node->bounds.Reset();
node->firstPrimOffset = 0;
node->nPrimitives = 0;
node->splitAxis = 0;
node->children[0] = NULL;
node->children[1] = NULL;
// Compute bounds of all primitives in BVH node
CBBOX bounds;
bounds.Reset();
for( int i = start; i < end; ++i )
bounds.Union( primitiveInfo[i].bounds );
int nPrimitives = end - start;
if( nPrimitives == 1 )
{
// Create leaf _BVHBuildNode_
int firstPrimOffset = orderedPrims.size();
for( int i = start; i < end; ++i )
{
int primitiveNr = primitiveInfo[i].primitiveNumber;
wxASSERT( primitiveNr < (int)m_primitives.size() );
orderedPrims.push_back( m_primitives[ primitiveNr ] );
}
node->InitLeaf( firstPrimOffset, nPrimitives, bounds );
}
else
{
// Compute bound of primitive centroids, choose split dimension _dim_
CBBOX centroidBounds;
centroidBounds.Reset();
for( int i = start; i < end; ++i )
centroidBounds.Union( primitiveInfo[i].centroid );
const int dim = centroidBounds.MaxDimension();
// Partition primitives into two sets and build children
int mid = (start + end) / 2;
if( fabs( centroidBounds.Max()[dim] -
centroidBounds.Min()[dim] ) < (FLT_EPSILON + FLT_EPSILON) )
{
// Create leaf _BVHBuildNode_
const int firstPrimOffset = orderedPrims.size();
for( int i = start; i < end; ++i )
{
int primitiveNr = primitiveInfo[i].primitiveNumber;
wxASSERT( (primitiveNr >= 0) &&
(primitiveNr < (int)m_primitives.size()) );
const COBJECT *obj = static_cast<const COBJECT *>( m_primitives[ primitiveNr ] );
wxASSERT( obj != NULL );
orderedPrims.push_back( obj );
}
node->InitLeaf( firstPrimOffset, nPrimitives, bounds );
}
else
{
// Partition primitives based on _splitMethod_
switch( m_splitMethod )
{
case SPLIT_MIDDLE:
{
// Partition primitives through node's midpoint
float pmid = centroidBounds.GetCenter( dim );
BVHPrimitiveInfo *midPtr = std::partition( &primitiveInfo[start],
&primitiveInfo[end - 1] + 1,
CompareToMid( dim, pmid ) );
mid = midPtr - &primitiveInfo[0];
wxASSERT( (mid >= start) &&
(mid <= end) );
if( (mid != start) && (mid != end) )
// for lots of prims with large overlapping bounding boxes, this
// may fail to partition; in that case don't break and fall through
// to SPLIT_EQUAL_COUNTS
break;
}
case SPLIT_EQUALCOUNTS:
{
// Partition primitives into equally-sized subsets
mid = (start + end) / 2;
std::nth_element( &primitiveInfo[start],
&primitiveInfo[mid],
&primitiveInfo[end - 1] + 1,
ComparePoints( dim ) );
break;
}
case SPLIT_SAH:
default:
{
// Partition primitives using approximate SAH
if( nPrimitives <= 2 )
{
// Partition primitives into equally-sized subsets
mid = (start + end) / 2;
std::nth_element( &primitiveInfo[start],
&primitiveInfo[mid],
&primitiveInfo[end - 1] + 1,
ComparePoints( dim ) );
}
else
{
// Allocate _BucketInfo_ for SAH partition buckets
const int nBuckets = 12;
BucketInfo buckets[nBuckets];
for( int i = 0; i < nBuckets; ++i )
{
buckets[i].count = 0;
buckets[i].bounds.Reset();
}
// Initialize _BucketInfo_ for SAH partition buckets
for( int i = start; i < end; ++i )
{
int b = nBuckets *
centroidBounds.Offset( primitiveInfo[i].centroid )[dim];
if( b == nBuckets )
b = nBuckets - 1;
wxASSERT( b >= 0 && b < nBuckets );
buckets[b].count++;
buckets[b].bounds.Union( primitiveInfo[i].bounds );
}
// Compute costs for splitting after each bucket
float cost[nBuckets - 1];
for( int i = 0; i < (nBuckets - 1); ++i )
{
CBBOX b0, b1;
b0.Reset();
b1.Reset();
int count0 = 0;
int count1 = 0;
for( int j = 0; j <= i; ++j )
{
if( buckets[j].count )
{
count0 += buckets[j].count;
b0.Union( buckets[j].bounds );
}
}
for( int j = i + 1; j < nBuckets; ++j )
{
if( buckets[j].count )
{
count1 += buckets[j].count;
b1.Union( buckets[j].bounds );
}
}
cost[i] = 1.0f +
( count0 * b0.SurfaceArea() +
count1 * b1.SurfaceArea() ) /
bounds.SurfaceArea();
}
// Find bucket to split at that minimizes SAH metric
float minCost = cost[0];
int minCostSplitBucket = 0;
for( int i = 1; i < (nBuckets - 1); ++i )
{
if( cost[i] < minCost )
{
minCost = cost[i];
minCostSplitBucket = i;
}
}
// Either create leaf or split primitives at selected SAH
// bucket
if( (nPrimitives > m_maxPrimsInNode) ||
(minCost < (float)nPrimitives) )
{
BVHPrimitiveInfo *pmid =
std::partition( &primitiveInfo[start],
&primitiveInfo[end - 1] + 1,
CompareToBucket( minCostSplitBucket,
nBuckets,
dim,
centroidBounds ) );
mid = pmid - &primitiveInfo[0];
wxASSERT( (mid >= start) &&
(mid <= end) );
}
else
{
// Create leaf _BVHBuildNode_
const int firstPrimOffset = orderedPrims.size();
for( int i = start; i < end; ++i )
{
const int primitiveNr = primitiveInfo[i].primitiveNumber;
wxASSERT( primitiveNr < (int)m_primitives.size() );
orderedPrims.push_back( m_primitives[ primitiveNr ] );
}
node->InitLeaf( firstPrimOffset, nPrimitives, bounds );
return node;
}
}
break;
}
}
node->InitInterior( dim,
recursiveBuild( primitiveInfo,
start,
mid,
totalNodes,
orderedPrims ),
recursiveBuild( primitiveInfo,
mid,
end,
totalNodes,
orderedPrims) );
}
}
return node;
}
BVHBuildNode *BVHAccel::recursiveBuild(MemoryArena &buildArena,
vector<BVHPrimitiveInfo> &buildData, uint32_t start,
uint32_t end, uint32_t *totalNodes,
vector<Reference<Primitive> > &orderedPrims) {
Assert(start != end);
(*totalNodes)++;
BVHBuildNode *node = buildArena.Alloc<BVHBuildNode>();
// Compute bounds of all primitives in BVH node
BBox bbox;
for (uint32_t i = start; i < end; ++i)
bbox = Union(bbox, buildData[i].bounds);
uint32_t nPrimitives = end - start;
if (nPrimitives == 1) {
// Create leaf _BVHBuildNode_
uint32_t firstPrimOffset = orderedPrims.size();
for (uint32_t i = start; i < end; ++i) {
uint32_t primNum = buildData[i].primitiveNumber;
orderedPrims.push_back(primitives[primNum]);
}
node->InitLeaf(firstPrimOffset, nPrimitives, bbox);
}
else {
// Compute bound of primitive centroids, choose split dimension _dim_
BBox centroidBounds;
for (uint32_t i = start; i < end; ++i)
centroidBounds = Union(centroidBounds, buildData[i].centroid);
int dim = centroidBounds.MaximumExtent();
// Partition primitives into two sets and build children
uint32_t mid = (start + end) / 2;
if (centroidBounds.pMax[dim] == centroidBounds.pMin[dim]) {
// Create leaf _BVHBuildNode_
uint32_t firstPrimOffset = orderedPrims.size();
for (uint32_t i = start; i < end; ++i) {
uint32_t primNum = buildData[i].primitiveNumber;
orderedPrims.push_back(primitives[primNum]);
}
node->InitLeaf(firstPrimOffset, nPrimitives, bbox);
return node;
}
// Partition primitives based on _splitMethod_
switch (splitMethod) {
case SPLIT_MIDDLE: {
// Partition primitives through node's midpoint
float pmid = .5f * (centroidBounds.pMin[dim] + centroidBounds.pMax[dim]);
BVHPrimitiveInfo *midPtr = std::partition(&buildData[start],
&buildData[end-1]+1,
CompareToMid(dim, pmid));
mid = midPtr - &buildData[0];
if (mid != start && mid != end)
// for lots of prims with large overlapping bounding boxes, this
// may fail to partition; in that case don't break and fall through
// to SPLIT_EQUAL_COUNTS
break;
}
case SPLIT_EQUAL_COUNTS: {
// Partition primitives into equally-sized subsets
mid = (start + end) / 2;
std::nth_element(&buildData[start], &buildData[mid],
&buildData[end-1]+1, ComparePoints(dim));
break;
}
case SPLIT_SAH: default: {
// Partition primitives using approximate SAH
if (nPrimitives <= 4) {
// Partition primitives into equally-sized subsets
mid = (start + end) / 2;
std::nth_element(&buildData[start], &buildData[mid],
&buildData[end-1]+1, ComparePoints(dim));
}
else {
// Allocate _BucketInfo_ for SAH partition buckets
const int nBuckets = 12;
struct BucketInfo {
BucketInfo() { count = 0; }
int count;
BBox bounds;
};
BucketInfo buckets[nBuckets];
// Initialize _BucketInfo_ for SAH partition buckets
for (uint32_t i = start; i < end; ++i) {
int b = nBuckets *
((buildData[i].centroid[dim] - centroidBounds.pMin[dim]) /
(centroidBounds.pMax[dim] - centroidBounds.pMin[dim]));
if (b == nBuckets) b = nBuckets-1;
Assert(b >= 0 && b < nBuckets);
buckets[b].count++;
buckets[b].bounds = Union(buckets[b].bounds, buildData[i].bounds);
}
// Compute costs for splitting after each bucket
float cost[nBuckets-1];
for (int i = 0; i < nBuckets-1; ++i) {
BBox b0, b1;
int count0 = 0, count1 = 0;
for (int j = 0; j <= i; ++j) {
b0 = Union(b0, buckets[j].bounds);
count0 += buckets[j].count;
}
for (int j = i+1; j < nBuckets; ++j) {
b1 = Union(b1, buckets[j].bounds);
count1 += buckets[j].count;
}
cost[i] = .125f + (count0*b0.SurfaceArea() + count1*b1.SurfaceArea()) /
bbox.SurfaceArea();
}
// Find bucket to split at that minimizes SAH metric
float minCost = cost[0];
uint32_t minCostSplit = 0;
for (int i = 1; i < nBuckets-1; ++i) {
if (cost[i] < minCost) {
minCost = cost[i];
minCostSplit = i;
}
}
// Either create leaf or split primitives at selected SAH bucket
if (nPrimitives > maxPrimsInNode ||
minCost < nPrimitives) {
BVHPrimitiveInfo *pmid = std::partition(&buildData[start],
&buildData[end-1]+1,
CompareToBucket(minCostSplit, nBuckets, dim, centroidBounds));
mid = pmid - &buildData[0];
}
else {
// Create leaf _BVHBuildNode_
uint32_t firstPrimOffset = orderedPrims.size();
for (uint32_t i = start; i < end; ++i) {
uint32_t primNum = buildData[i].primitiveNumber;
orderedPrims.push_back(primitives[primNum]);
}
node->InitLeaf(firstPrimOffset, nPrimitives, bbox);
return node;
}
}
break;
}
}
node->InitInterior(dim,
recursiveBuild(buildArena, buildData, start, mid,
totalNodes, orderedPrims),
recursiveBuild(buildArena, buildData, mid, end,
totalNodes, orderedPrims));
}
return node;
}
