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blender/intern/cycles/bvh/bvh_build.cpp

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/*
* Adapted from code copyright 2009-2010 NVIDIA Corporation
* Modifications Copyright 2011, Blender Foundation.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "bvh/bvh_binning.h"
#include "bvh/bvh_build.h"
#include "bvh/bvh_node.h"
#include "bvh/bvh_params.h"
#include "bvh_split.h"
#include "render/mesh.h"
#include "render/object.h"
#include "render/scene.h"
#include "render/curves.h"
#include "util/util_algorithm.h"
#include "util/util_debug.h"
#include "util/util_foreach.h"
#include "util/util_logging.h"
#include "util/util_progress.h"
#include "util/util_stack_allocator.h"
#include "util/util_simd.h"
#include "util/util_time.h"
#include "util/util_queue.h"
CCL_NAMESPACE_BEGIN
/* BVH Build Task */
class BVHBuildTask : public Task {
public:
BVHBuildTask(BVHBuild *build,
InnerNode *node,
int child,
const BVHObjectBinning& range,
int level)
: range_(range)
{
run = function_bind(&BVHBuild::thread_build_node,
build,
node,
child,
&range_,
level);
}
private:
BVHObjectBinning range_;
};
class BVHSpatialSplitBuildTask : public Task {
public:
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);
}
private:
BVHRange range_;
vector<BVHReference> references_;
};
/* Constructor / Destructor */
BVHBuild::BVHBuild(const vector<Object*>& objects_,
array<int>& prim_type_,
array<int>& prim_index_,
array<int>& prim_object_,
array<float2>& prim_time_,
const BVHParams& params_,
Progress& progress_)
: objects(objects_),
prim_type(prim_type_),
prim_index(prim_index_),
prim_object(prim_object_),
prim_time(prim_time_),
params(params_),
progress(progress_),
progress_start_time(0.0),
unaligned_heuristic(objects_)
{
spatial_min_overlap = 0.0f;
}
BVHBuild::~BVHBuild()
{
}
/* Adding References */
void BVHBuild::add_reference_triangles(BoundBox& root, BoundBox& center, Mesh *mesh, int i)
{
const Attribute *attr_mP = NULL;
if(mesh->has_motion_blur()) {
attr_mP = mesh->attributes.find(ATTR_STD_MOTION_VERTEX_POSITION);
}
const size_t num_triangles = mesh->num_triangles();
for(uint j = 0; j < num_triangles; j++) {
Mesh::Triangle t = mesh->get_triangle(j);
const float3 *verts = &mesh->verts[0];
if(attr_mP == NULL) {
BoundBox bounds = BoundBox::empty;
t.bounds_grow(verts, bounds);
if(bounds.valid()) {
references.push_back(BVHReference(bounds,
j,
i,
PRIMITIVE_TRIANGLE));
root.grow(bounds);
center.grow(bounds.center2());
}
}
else if(params.num_motion_triangle_steps == 0 || params.use_spatial_split) {
/* Motion triangles, simple case: single node for the whole
* primitive. Lowest memory footprint and faster BVH build but
* least optimal ray-tracing.
*/
/* TODO(sergey): Support motion steps for spatially split BVH. */
const size_t num_verts = mesh->verts.size();
const size_t num_steps = mesh->motion_steps;
const float3 *vert_steps = attr_mP->data_float3();
BoundBox bounds = BoundBox::empty;
t.bounds_grow(verts, bounds);
for(size_t step = 0; step < num_steps - 1; step++) {
t.bounds_grow(vert_steps + step*num_verts, bounds);
}
if(bounds.valid()) {
references.push_back(
BVHReference(bounds,
j,
i,
PRIMITIVE_MOTION_TRIANGLE));
root.grow(bounds);
center.grow(bounds.center2());
}
}
else {
/* Motion triangles, trace optimized case: we split triangle
* primitives into separate nodes for each of the time steps.
* This way we minimize overlap of neighbor curve primitives.
*/
const int num_bvh_steps = params.num_motion_curve_steps * 2 + 1;
const float num_bvh_steps_inv_1 = 1.0f / (num_bvh_steps - 1);
const size_t num_verts = mesh->verts.size();
const size_t num_steps = mesh->motion_steps;
const float3 *vert_steps = attr_mP->data_float3();
/* Calculate bounding box of the previous time step.
* Will be reused later to avoid duplicated work on
* calculating BVH time step boundbox.
*/
float3 prev_verts[3];
t.motion_verts(verts,
vert_steps,
num_verts,
num_steps,
0.0f,
prev_verts);
BoundBox prev_bounds = BoundBox::empty;
prev_bounds.grow(prev_verts[0]);
prev_bounds.grow(prev_verts[1]);
prev_bounds.grow(prev_verts[2]);
/* Create all primitive time steps, */
for(int bvh_step = 1; bvh_step < num_bvh_steps; ++bvh_step) {
const float curr_time = (float)(bvh_step) * num_bvh_steps_inv_1;
float3 curr_verts[3];
t.motion_verts(verts,
vert_steps,
num_verts,
num_steps,
curr_time,
curr_verts);
BoundBox curr_bounds = BoundBox::empty;
curr_bounds.grow(curr_verts[0]);
curr_bounds.grow(curr_verts[1]);
curr_bounds.grow(curr_verts[2]);
BoundBox bounds = prev_bounds;
bounds.grow(curr_bounds);
if(bounds.valid()) {
const float prev_time = (float)(bvh_step - 1) * num_bvh_steps_inv_1;
references.push_back(
BVHReference(bounds,
j,
i,
PRIMITIVE_MOTION_TRIANGLE,
prev_time,
curr_time));
root.grow(bounds);
center.grow(bounds.center2());
}
/* Current time boundbox becomes previous one for the
* next time step.
*/
prev_bounds = curr_bounds;
}
}
}
}
void BVHBuild::add_reference_curves(BoundBox& root, BoundBox& center, Mesh *mesh, int i)
{
const Attribute *curve_attr_mP = NULL;
if(mesh->has_motion_blur()) {
curve_attr_mP = mesh->curve_attributes.find(ATTR_STD_MOTION_VERTEX_POSITION);
}
const size_t num_curves = mesh->num_curves();
for(uint j = 0; j < num_curves; j++) {
const Mesh::Curve curve = mesh->get_curve(j);
const float *curve_radius = &mesh->curve_radius[0];
for(int k = 0; k < curve.num_keys - 1; k++) {
if(curve_attr_mP == NULL) {
/* Really simple logic for static hair. */
BoundBox bounds = BoundBox::empty;
curve.bounds_grow(k, &mesh->curve_keys[0], curve_radius, bounds);
if(bounds.valid()) {
int packed_type = PRIMITIVE_PACK_SEGMENT(PRIMITIVE_CURVE, k);
references.push_back(BVHReference(bounds, j, i, packed_type));
root.grow(bounds);
center.grow(bounds.center2());
}
}
else if(params.num_motion_curve_steps == 0 || params.use_spatial_split) {
/* Simple case of motion curves: single node for the while
* shutter time. Lowest memory usage but less optimal
* rendering.
*/
/* TODO(sergey): Support motion steps for spatially split BVH. */
BoundBox bounds = BoundBox::empty;
curve.bounds_grow(k, &mesh->curve_keys[0], curve_radius, bounds);
const size_t num_keys = mesh->curve_keys.size();
const size_t num_steps = mesh->motion_steps;
const float3 *key_steps = curve_attr_mP->data_float3();
for(size_t step = 0; step < num_steps - 1; step++) {
curve.bounds_grow(k,
key_steps + step*num_keys,
curve_radius,
bounds);
}
if(bounds.valid()) {
int packed_type = PRIMITIVE_PACK_SEGMENT(PRIMITIVE_MOTION_CURVE, k);
references.push_back(BVHReference(bounds,
j,
i,
packed_type));
root.grow(bounds);
center.grow(bounds.center2());
}
}
else {
/* Motion curves, trace optimized case: we split curve keys
* primitives into separate nodes for each of the time steps.
* This way we minimize overlap of neighbor curve primitives.
*/
const int num_bvh_steps = params.num_motion_curve_steps * 2 + 1;
const float num_bvh_steps_inv_1 = 1.0f / (num_bvh_steps - 1);
const size_t num_steps = mesh->motion_steps;
const float3 *curve_keys = &mesh->curve_keys[0];
const float3 *key_steps = curve_attr_mP->data_float3();
const size_t num_keys = mesh->curve_keys.size();
/* Calculate bounding box of the previous time step.
* Will be reused later to avoid duplicated work on
* calculating BVH time step boundbox.
*/
float4 prev_keys[4];
curve.cardinal_motion_keys(curve_keys,
curve_radius,
key_steps,
num_keys,
num_steps,
0.0f,
k - 1, k, k + 1, k + 2,
prev_keys);
BoundBox prev_bounds = BoundBox::empty;
curve.bounds_grow(prev_keys, prev_bounds);
/* Create all primitive time steps, */
for(int bvh_step = 1; bvh_step < num_bvh_steps; ++bvh_step) {
const float curr_time = (float)(bvh_step) * num_bvh_steps_inv_1;
float4 curr_keys[4];
curve.cardinal_motion_keys(curve_keys,
curve_radius,
key_steps,
num_keys,
num_steps,
curr_time,
k - 1, k, k + 1, k + 2,
curr_keys);
BoundBox curr_bounds = BoundBox::empty;
curve.bounds_grow(curr_keys, curr_bounds);
BoundBox bounds = prev_bounds;
bounds.grow(curr_bounds);
if(bounds.valid()) {
const float prev_time = (float)(bvh_step - 1) * num_bvh_steps_inv_1;
int packed_type = PRIMITIVE_PACK_SEGMENT(PRIMITIVE_MOTION_CURVE, k);
references.push_back(BVHReference(bounds,
j,
i,
packed_type,
prev_time,
curr_time));
root.grow(bounds);
center.grow(bounds.center2());
}
/* Current time boundbox becomes previous one for the
* next time step.
*/
prev_bounds = curr_bounds;
}
}
}
}
}
void BVHBuild::add_reference_mesh(BoundBox& root, BoundBox& center, Mesh *mesh, int i)
{
if(params.primitive_mask & PRIMITIVE_ALL_TRIANGLE) {
add_reference_triangles(root, center, mesh, i);
}
if(params.primitive_mask & PRIMITIVE_ALL_CURVE) {
add_reference_curves(root, center, mesh, i);
}
}
void BVHBuild::add_reference_object(BoundBox& root, BoundBox& center, Object *ob, int i)
{
references.push_back(BVHReference(ob->bounds, -1, i, 0));
root.grow(ob->bounds);
center.grow(ob->bounds.center2());
}
static size_t count_curve_segments(Mesh *mesh)
{
size_t num = 0, num_curves = mesh->num_curves();
for(size_t i = 0; i < num_curves; i++)
num += mesh->get_curve(i).num_keys - 1;
return num;
}
void BVHBuild::add_references(BVHRange& root)
{
/* reserve space for references */
size_t num_alloc_references = 0;
foreach(Object *ob, objects) {
if(params.top_level) {
if(!ob->is_traceable()) {
continue;
}
if(!ob->mesh->is_instanced()) {
if(params.primitive_mask & PRIMITIVE_ALL_TRIANGLE) {
num_alloc_references += ob->mesh->num_triangles();
}
if(params.primitive_mask & PRIMITIVE_ALL_CURVE) {
num_alloc_references += count_curve_segments(ob->mesh);
}
}
else
num_alloc_references++;
}
else {
if(params.primitive_mask & PRIMITIVE_ALL_TRIANGLE) {
num_alloc_references += ob->mesh->num_triangles();
}
if(params.primitive_mask & PRIMITIVE_ALL_CURVE) {
num_alloc_references += count_curve_segments(ob->mesh);
}
}
}
references.reserve(num_alloc_references);
/* add references from objects */
BoundBox bounds = BoundBox::empty, center = BoundBox::empty;
int i = 0;
foreach(Object *ob, objects) {
if(params.top_level) {
if(!ob->is_traceable()) {
++i;
continue;
}
if(!ob->mesh->is_instanced())
add_reference_mesh(bounds, center, ob->mesh, i);
else
add_reference_object(bounds, center, ob, i);
}
else
add_reference_mesh(bounds, center, ob->mesh, i);
i++;
if(progress.get_cancel()) return;
}
/* happens mostly on empty meshes */
if(!bounds.valid())
bounds.grow(make_float3(0.0f, 0.0f, 0.0f));
root = BVHRange(bounds, center, 0, references.size());
}
/* Build */
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);
}
spatial_free_index = 0;
need_prim_time = params.num_motion_curve_steps > 0 ||
params.num_motion_triangle_steps > 0;
/* init progress updates */
double build_start_time;
build_start_time = 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());
if(need_prim_time) {
prim_time.resize(references.size());
}
else {
prim_time.resize(0);
}
/* build recursively */
BVHNode *rootnode;
if(params.use_spatial_split) {
/* Perform multithreaded spatial split build. */
rootnode = build_node(root, &references, 0, 0);
task_pool.wait_work();
}
else {
/* Perform 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;
VLOG(1) << "BVH build cancelled.";
}
else {
/*rotate(rootnode, 4, 5);*/
rootnode->update_visibility();
rootnode->update_time();
}
if(rootnode != NULL) {
VLOG(1) << "BVH build statistics:\n"
<< " Build time: " << time_dt() - build_start_time << "\n"
<< " Total number of nodes: "
<< string_human_readable_number(rootnode->getSubtreeSize(BVH_STAT_NODE_COUNT)) << "\n"
<< " Number of inner nodes: "
<< string_human_readable_number(rootnode->getSubtreeSize(BVH_STAT_INNER_COUNT)) << "\n"
<< " Number of leaf nodes: "
<< string_human_readable_number(rootnode->getSubtreeSize(BVH_STAT_LEAF_COUNT)) << "\n"
<< " Number of unaligned nodes: "
<< string_human_readable_number(rootnode->getSubtreeSize(BVH_STAT_UNALIGNED_COUNT)) << "\n"
<< " Allocation slop factor: "
<< ((prim_type.capacity() != 0)
? (float)prim_type.size() / prim_type.capacity()
: 1.0f) << "\n";
}
}
return rootnode;
}
void BVHBuild::progress_update()
{
if(time_dt() - progress_start_time < 0.25)
return;
double progress_start = (double)progress_count/(double)progress_total;
double duplicates = (double)(progress_total - progress_original_total)/(double)progress_total;
string msg = string_printf("Building BVH %.0f%%, duplicates %.0f%%",
progress_start * 100.0, duplicates * 100.0);
progress.set_substatus(msg);
progress_start_time = time_dt();
}
void BVHBuild::thread_build_node(InnerNode *inner,
int child,
BVHObjectBinning *range,
int level)
{
if(progress.get_cancel())
return;
/* build nodes */
BVHNode *node = build_node(*range, level);
/* set child in inner node */
inner->children[child] = node;
/* update progress */
if(range->size() < THREAD_TASK_SIZE) {
/*rotate(node, INT_MAX, 5);*/
thread_scoped_lock lock(build_mutex);
progress_count += range->size();
progress_update();
}
}
void BVHBuild::thread_build_spatial_split_node(InnerNode *inner,
int child,
BVHRange *range,
vector<BVHReference> *references,
int level,
int thread_id)
{
if(progress.get_cancel()) {
return;
}
/* build nodes */
BVHNode *node = build_node(*range, references, level, thread_id);
/* set child in inner node */
inner->children[child] = node;
}
bool BVHBuild::range_within_max_leaf_size(const BVHRange& range,
const vector<BVHReference>& references) const
{
size_t size = range.size();
size_t max_leaf_size = max(params.max_triangle_leaf_size, params.max_curve_leaf_size);
if(size > max_leaf_size)
return false;
size_t num_triangles = 0;
size_t num_motion_triangles = 0;
size_t num_curves = 0;
size_t num_motion_curves = 0;
for(int i = 0; i < size; i++) {
const BVHReference& ref = references[range.start() + i];
if(ref.prim_type() & PRIMITIVE_CURVE)
num_curves++;
if(ref.prim_type() & PRIMITIVE_MOTION_CURVE)
num_motion_curves++;
else if(ref.prim_type() & PRIMITIVE_TRIANGLE)
num_triangles++;
else if(ref.prim_type() & PRIMITIVE_MOTION_TRIANGLE)
num_motion_triangles++;
}
return (num_triangles <= params.max_triangle_leaf_size) &&
(num_motion_triangles <= params.max_motion_triangle_leaf_size) &&
(num_curves <= params.max_curve_leaf_size) &&
(num_motion_curves <= params.max_motion_curve_leaf_size);
}
/* multithreaded binning builder */
BVHNode* BVHBuild::build_node(const BVHObjectBinning& range, int level)
{
size_t size = range.size();
float leafSAH = params.sah_primitive_cost * range.leafSAH;
float splitSAH = params.sah_node_cost * range.bounds().half_area() + params.sah_primitive_cost * range.splitSAH;
/* Have at least one inner node on top level, for performance and correct
* visibility tests, since object instances do not check visibility flag.
*/
if(!(range.size() > 0 && params.top_level && level == 0)) {
/* Make leaf node when threshold reached or SAH tells us. */
if((params.small_enough_for_leaf(size, level)) ||
(range_within_max_leaf_size(range, references) && leafSAH < splitSAH))
{
return create_leaf_node(range, references);
}
}
BVHObjectBinning unaligned_range;
float unalignedSplitSAH = FLT_MAX;
float unalignedLeafSAH = FLT_MAX;
Transform aligned_space;
bool do_unalinged_split = false;
if(params.use_unaligned_nodes &&
splitSAH > params.unaligned_split_threshold*leafSAH)
{
aligned_space = unaligned_heuristic.compute_aligned_space(
range, &references[0]);
unaligned_range = BVHObjectBinning(range,
&references[0],
&unaligned_heuristic,
&aligned_space);
unalignedSplitSAH = params.sah_node_cost * unaligned_range.unaligned_bounds().half_area() +
params.sah_primitive_cost * unaligned_range.splitSAH;
unalignedLeafSAH = params.sah_primitive_cost * unaligned_range.leafSAH;
if(!(range.size() > 0 && params.top_level && level == 0)) {
if(unalignedLeafSAH < unalignedSplitSAH && unalignedSplitSAH < splitSAH &&
range_within_max_leaf_size(range, references))
{
return create_leaf_node(range, references);
}
}
/* Check whether unaligned split is better than the regulat one. */
if(unalignedSplitSAH < splitSAH) {
do_unalinged_split = true;
}
}
/* Perform split. */
BVHObjectBinning left, right;
if(do_unalinged_split) {
unaligned_range.split(&references[0], left, right);
}
else {
range.split(&references[0], left, right);
}
BoundBox bounds;
if(do_unalinged_split) {
bounds = unaligned_heuristic.compute_aligned_boundbox(
range, &references[0], aligned_space);
}
else {
bounds = range.bounds();
}
/* Create inner node. */
InnerNode *inner;
if(range.size() < THREAD_TASK_SIZE) {
/* local build */
BVHNode *leftnode = build_node(left, level + 1);
BVHNode *rightnode = build_node(right, level + 1);
inner = new InnerNode(bounds, leftnode, rightnode);
}
else {
/* Threaded build */
inner = new InnerNode(bounds);
task_pool.push(new BVHBuildTask(this, inner, 0, left, level + 1), true);
task_pool.push(new BVHBuildTask(this, inner, 1, right, level + 1), true);
}
if(do_unalinged_split) {
inner->set_aligned_space(aligned_space);
}
return inner;
}
/* multithreaded spatial split builder */
BVHNode* BVHBuild::build_node(const BVHRange& range,
vector<BVHReference> *references,
int level,
int thread_id)
{
/* Update progress.
*
* TODO(sergey): Currently it matches old behavior, but we can move it to the
* task thread (which will mimic non=split builder) and save some CPU ticks
* on checking cancel status.
*/
progress_update();
if(progress.get_cancel()) {
return NULL;
}
/* Small enough or too deep => create leaf. */
if(!(range.size() > 0 && params.top_level && level == 0)) {
if(params.small_enough_for_leaf(range.size(), level)) {
progress_count += range.size();
return create_leaf_node(range, *references);
}
}
/* Perform splitting test. */
BVHSpatialStorage *storage = &spatial_storage[thread_id];
BVHMixedSplit split(this, storage, range, references, level);
if(!(range.size() > 0 && params.top_level && level == 0)) {
if(split.no_split) {
progress_count += range.size();
return create_leaf_node(range, *references);
}
}
float leafSAH = params.sah_primitive_cost * split.leafSAH;
float splitSAH = params.sah_node_cost * range.bounds().half_area() +
params.sah_primitive_cost * split.nodeSAH;
BVHMixedSplit unaligned_split;
float unalignedSplitSAH = FLT_MAX;
/* float unalignedLeafSAH = FLT_MAX; */
Transform aligned_space;
bool do_unalinged_split = false;
if(params.use_unaligned_nodes &&
splitSAH > params.unaligned_split_threshold*leafSAH)
{
aligned_space =
unaligned_heuristic.compute_aligned_space(range, &references->at(0));
unaligned_split = BVHMixedSplit(this,
storage,
range,
references,
level,
&unaligned_heuristic,
&aligned_space);
/* unalignedLeafSAH = params.sah_primitive_cost * split.leafSAH; */
unalignedSplitSAH = params.sah_node_cost * unaligned_split.bounds.half_area() +
params.sah_primitive_cost * unaligned_split.nodeSAH;
/* TOOD(sergey): Check we can create leaf already. */
/* Check whether unaligned split is better than the regulat one. */
if(unalignedSplitSAH < splitSAH) {
do_unalinged_split = true;
}
}
/* Do split. */
BVHRange left, right;
if(do_unalinged_split) {
unaligned_split.split(this, left, right, range);
}
else {
split.split(this, left, right, range);
}
progress_total += left.size() + right.size() - range.size();
BoundBox bounds;
if(do_unalinged_split) {
bounds = unaligned_heuristic.compute_aligned_boundbox(
range, &references->at(0), aligned_space);
}
else {
bounds = range.bounds();
}
/* Create inner node. */
InnerNode *inner;
if(range.size() < THREAD_TASK_SIZE) {
/* Local build. */
/* Build left node. */
vector<BVHReference> copy(references->begin() + right.start(),
references->begin() + right.end());
right.set_start(0);
BVHNode *leftnode = build_node(left, references, level + 1, thread_id);
/* Build right node. */
BVHNode *rightnode = build_node(right, &copy, level + 1, thread_id);
inner = new InnerNode(bounds, leftnode, rightnode);
}
else {
/* Threaded build. */
inner = new InnerNode(bounds);
task_pool.push(new BVHSpatialSplitBuildTask(this,
inner,
0,
left,
*references,
level + 1),
true);
task_pool.push(new BVHSpatialSplitBuildTask(this,
inner,
1,
right,
*references,
level + 1),
true);
}
if(do_unalinged_split) {
inner->set_aligned_space(aligned_space);
}
return inner;
}
/* Create Nodes */
BVHNode *BVHBuild::create_object_leaf_nodes(const BVHReference *ref, int start, int num)
{
if(num == 0) {
BoundBox bounds = BoundBox::empty;
return new LeafNode(bounds, 0, 0, 0);
}
else if(num == 1) {
assert(start < prim_type.size());
prim_type[start] = ref->prim_type();
prim_index[start] = ref->prim_index();
prim_object[start] = ref->prim_object();
if(need_prim_time) {
prim_time[start] = make_float2(ref->time_from(), ref->time_to());
}
uint visibility = objects[ref->prim_object()]->visibility;
BVHNode *leaf_node = new LeafNode(ref->bounds(), visibility, start, start+1);
leaf_node->time_from = ref->time_from();
leaf_node->time_to = ref->time_to();
return leaf_node;
}
else {
int mid = num/2;
BVHNode *leaf0 = create_object_leaf_nodes(ref, start, mid);
BVHNode *leaf1 = create_object_leaf_nodes(ref+mid, start+mid, num-mid);
BoundBox bounds = BoundBox::empty;
bounds.grow(leaf0->bounds);
bounds.grow(leaf1->bounds);
BVHNode *inner_node = new InnerNode(bounds, leaf0, leaf1);
inner_node->time_from = min(leaf0->time_from, leaf1->time_from);
inner_node->time_to = max(leaf0->time_to, leaf1->time_to);
return inner_node;
}
}
BVHNode* BVHBuild::create_leaf_node(const BVHRange& range,
const vector<BVHReference>& references)
{
/* This is a bit overallocating here (considering leaf size into account),
* but chunk-based re-allocation in vector makes it difficult to use small
* size of stack storage here. Some tweaks are possible tho.
*
* NOTES:
* - If the size is too big, we'll have inefficient stack usage,
* and lots of cache misses.
* - If the size is too small, then we can run out of memory
* allowed to be used by vector.
* In practice it wouldn't mean crash, just allocator will fallback
* to heap which is slower.
* - Optimistic re-allocation in STL could jump us out of stack usage
* because re-allocation happens in chunks and size of those chunks we
* can not control.
*/
typedef StackAllocator<256, int> LeafStackAllocator;
typedef StackAllocator<256, float2> LeafTimeStackAllocator;
typedef StackAllocator<256, BVHReference> LeafReferenceStackAllocator;
vector<int, LeafStackAllocator> p_type[PRIMITIVE_NUM_TOTAL];
vector<int, LeafStackAllocator> p_index[PRIMITIVE_NUM_TOTAL];
vector<int, LeafStackAllocator> p_object[PRIMITIVE_NUM_TOTAL];
vector<float2, LeafTimeStackAllocator> p_time[PRIMITIVE_NUM_TOTAL];
vector<BVHReference, LeafReferenceStackAllocator> p_ref[PRIMITIVE_NUM_TOTAL];
/* TODO(sergey): In theory we should be able to store references. */
vector<BVHReference, LeafReferenceStackAllocator> object_references;
uint visibility[PRIMITIVE_NUM_TOTAL] = {0};
/* NOTE: Keep initializtion in sync with actual number of primitives. */
BoundBox bounds[PRIMITIVE_NUM_TOTAL] = {BoundBox::empty,
BoundBox::empty,
BoundBox::empty,
BoundBox::empty};
int ob_num = 0;
int num_new_prims = 0;
/* Fill in per-type type/index array. */
for(int i = 0; i < range.size(); i++) {
const BVHReference& ref = references[range.start() + i];
if(ref.prim_index() != -1) {
int type_index = bitscan(ref.prim_type() & PRIMITIVE_ALL);
p_ref[type_index].push_back(ref);
p_type[type_index].push_back(ref.prim_type());
p_index[type_index].push_back(ref.prim_index());
p_object[type_index].push_back(ref.prim_object());
p_time[type_index].push_back(make_float2(ref.time_from(),
ref.time_to()));
bounds[type_index].grow(ref.bounds());
visibility[type_index] |= objects[ref.prim_object()]->visibility;
if(ref.prim_type() & PRIMITIVE_ALL_CURVE) {
visibility[type_index] |= PATH_RAY_CURVE;
}
++num_new_prims;
}
else {
object_references.push_back(ref);
++ob_num;
}
}
/* Create leaf nodes for every existing primitive.
*
* Here we write primitive types, indices and objects to a temporary array.
* This way we keep all the heavy memory allocation code outside of the
* thread lock in the case of spatial split building.
*
* TODO(sergey): With some pointer trickery we can write directly to the
* destination buffers for the non-spatial split BVH.
*/
BVHNode *leaves[PRIMITIVE_NUM_TOTAL + 1] = {NULL};
int num_leaves = 0;
size_t start_index = 0;
vector<int, LeafStackAllocator> local_prim_type,
local_prim_index,
local_prim_object;
vector<float2, LeafTimeStackAllocator> local_prim_time;
local_prim_type.resize(num_new_prims);
local_prim_index.resize(num_new_prims);
local_prim_object.resize(num_new_prims);
if(need_prim_time) {
local_prim_time.resize(num_new_prims);
}
for(int i = 0; i < PRIMITIVE_NUM_TOTAL; ++i) {
int num = (int)p_type[i].size();
if(num != 0) {
assert(p_type[i].size() == p_index[i].size());
assert(p_type[i].size() == p_object[i].size());
Transform aligned_space;
bool alignment_found = false;
for(int j = 0; j < num; ++j) {
const int index = start_index + j;
local_prim_type[index] = p_type[i][j];
local_prim_index[index] = p_index[i][j];
local_prim_object[index] = p_object[i][j];
if(need_prim_time) {
local_prim_time[index] = p_time[i][j];
}
if(params.use_unaligned_nodes && !alignment_found) {
alignment_found =
unaligned_heuristic.compute_aligned_space(p_ref[i][j],
&aligned_space);
}
}
LeafNode *leaf_node = new LeafNode(bounds[i],
visibility[i],
start_index,
start_index + num);
if(true) {
float time_from = 1.0f, time_to = 0.0f;
for(int j = 0; j < num; ++j) {
const BVHReference &ref = p_ref[i][j];
time_from = min(time_from, ref.time_from());
time_to = max(time_to, ref.time_to());
}
leaf_node->time_from = time_from;
leaf_node->time_to = time_to;
}
if(alignment_found) {
/* Need to recalculate leaf bounds with new alignment. */
leaf_node->bounds = BoundBox::empty;
for(int j = 0; j < num; ++j) {
const BVHReference &ref = p_ref[i][j];
BoundBox ref_bounds =
unaligned_heuristic.compute_aligned_prim_boundbox(
ref,
aligned_space);
leaf_node->bounds.grow(ref_bounds);
}
/* Set alignment space. */
leaf_node->set_aligned_space(aligned_space);
}
leaves[num_leaves++] = leaf_node;
start_index += num;
}
}
/* Get size of new data to be copied to the packed arrays. */
const int num_new_leaf_data = start_index;
const size_t new_leaf_data_size = sizeof(int) * num_new_leaf_data;
/* Copy actual data to the packed array. */
if(params.use_spatial_split) {
spatial_spin_lock.lock();
/* We use first free index in the packed arrays and mode pointer to the
* end of the current range.
*
* This doesn't give deterministic packed arrays, but it shouldn't really
* matter because order of children in BVH is deterministic.
*/
start_index = spatial_free_index;
spatial_free_index += range.size();
/* Extend an array when needed. */
const size_t range_end = start_index + range.size();
if(prim_type.size() < range_end) {
/* Avoid extra re-allocations by pre-allocating bigger array in an
* advance.
*/
if(range_end >= prim_type.capacity()) {
float progress = (float)progress_count/(float)progress_total;
float factor = (1.0f - progress);
const size_t reserve = (size_t)(range_end + (float)range_end*factor);
prim_type.reserve(reserve);
prim_index.reserve(reserve);
prim_object.reserve(reserve);
if(need_prim_time) {
prim_time.reserve(reserve);
}
}
prim_type.resize(range_end);
prim_index.resize(range_end);
prim_object.resize(range_end);
if(need_prim_time) {
prim_time.resize(range_end);
}
}
spatial_spin_lock.unlock();
/* Perform actual data copy. */
if(new_leaf_data_size > 0) {
memcpy(&prim_type[start_index], &local_prim_type[0], new_leaf_data_size);
memcpy(&prim_index[start_index], &local_prim_index[0], new_leaf_data_size);
memcpy(&prim_object[start_index], &local_prim_object[0], new_leaf_data_size);
if(need_prim_time) {
memcpy(&prim_time[start_index], &local_prim_time[0], sizeof(float2)*num_new_leaf_data);
}
}
}
else {
/* For the regular BVH builder we simply copy new data starting at the
* range start. This is totally thread-safe, all threads are living
* inside of their own range.
*/
start_index = range.start();
if(new_leaf_data_size > 0) {
memcpy(&prim_type[start_index], &local_prim_type[0], new_leaf_data_size);
memcpy(&prim_index[start_index], &local_prim_index[0], new_leaf_data_size);
memcpy(&prim_object[start_index], &local_prim_object[0], new_leaf_data_size);
if(need_prim_time) {
memcpy(&prim_time[start_index], &local_prim_time[0], sizeof(float2)*num_new_leaf_data);
}
}
}
/* So far leaves were created with the zero-based index in an arrays,
* here we modify the indices to correspond to actual packed array start
* index.
*/
for(int i = 0; i < num_leaves; ++i) {
LeafNode *leaf = (LeafNode *)leaves[i];
leaf->lo += start_index;
leaf->hi += start_index;
}
/* Create leaf node for object. */
if(num_leaves == 0 || ob_num) {
/* Only create object leaf nodes if there are objects or no other
* nodes created.
*/
const BVHReference *ref = (ob_num)? &object_references[0]: NULL;
leaves[num_leaves] = create_object_leaf_nodes(ref,
start_index + num_new_leaf_data,
ob_num);
++num_leaves;
}
/* TODO(sergey): Need to take care of alignment when number of leaves
* is more than 1.
*/
if(num_leaves == 1) {
/* Simplest case: single leaf, just return it.
* In all the rest cases we'll be creating intermediate inner node with
* an appropriate bounding box.
*/
return leaves[0];
}
else if(num_leaves == 2) {
return new InnerNode(range.bounds(), leaves[0], leaves[1]);
}
else if(num_leaves == 3) {
BoundBox inner_bounds = merge(leaves[1]->bounds, leaves[2]->bounds);
BVHNode *inner = new InnerNode(inner_bounds, leaves[1], leaves[2]);
return new InnerNode(range.bounds(), leaves[0], inner);
} else {
/* Should be doing more branches if more primitive types added. */
assert(num_leaves <= 5);
BoundBox inner_bounds_a = merge(leaves[0]->bounds, leaves[1]->bounds);
BoundBox inner_bounds_b = merge(leaves[2]->bounds, leaves[3]->bounds);
BVHNode *inner_a = new InnerNode(inner_bounds_a, leaves[0], leaves[1]);
BVHNode *inner_b = new InnerNode(inner_bounds_b, leaves[2], leaves[3]);
BoundBox inner_bounds_c = merge(inner_a->bounds, inner_b->bounds);
BVHNode *inner_c = new InnerNode(inner_bounds_c, inner_a, inner_b);
if(num_leaves == 5) {
return new InnerNode(range.bounds(), inner_c, leaves[4]);
}
return inner_c;
}
#undef MAX_ITEMS_PER_LEAF
}
/* Tree Rotations */
void BVHBuild::rotate(BVHNode *node, int max_depth, int iterations)
{
/* in tested scenes, this resulted in slightly slower raytracing, so disabled
* it for now. could be implementation bug, or depend on the scene */
if(node)
for(int i = 0; i < iterations; i++)
rotate(node, max_depth);
}
void BVHBuild::rotate(BVHNode *node, int max_depth)
{
/* nothing to rotate if we reached a leaf node. */
if(node->is_leaf() || max_depth < 0)
return;
InnerNode *parent = (InnerNode*)node;
/* rotate all children first */
for(size_t c = 0; c < 2; c++)
rotate(parent->children[c], max_depth-1);
/* compute current area of all children */
BoundBox bounds0 = parent->children[0]->bounds;
BoundBox bounds1 = parent->children[1]->bounds;
float area0 = bounds0.half_area();
float area1 = bounds1.half_area();
float4 child_area = make_float4(area0, area1, 0.0f, 0.0f);
/* find best rotation. we pick a target child of a first child, and swap
* this with an other child. we perform the best such swap. */
float best_cost = FLT_MAX;
int best_child = -1, best_target = -1, best_other = -1;
for(size_t c = 0; c < 2; c++) {
/* ignore leaf nodes as we cannot descent into */
if(parent->children[c]->is_leaf())
continue;
InnerNode *child = (InnerNode*)parent->children[c];
BoundBox& other = (c == 0)? bounds1: bounds0;
/* transpose child bounds */
BoundBox target0 = child->children[0]->bounds;
BoundBox target1 = child->children[1]->bounds;
/* compute cost for both possible swaps */
float cost0 = merge(other, target1).half_area() - child_area[c];
float cost1 = merge(target0, other).half_area() - child_area[c];
if(min(cost0,cost1) < best_cost) {
best_child = (int)c;
best_other = (int)(1-c);
if(cost0 < cost1) {
best_cost = cost0;
best_target = 0;
}
else {
best_cost = cost0;
best_target = 1;
}
}
}
/* if we did not find a swap that improves the SAH then do nothing */
if(best_cost >= 0)
return;
assert(best_child == 0 || best_child == 1);
assert(best_target != -1);
/* perform the best found tree rotation */
InnerNode *child = (InnerNode*)parent->children[best_child];
swap(parent->children[best_other], child->children[best_target]);
child->bounds = merge(child->children[0]->bounds, child->children[1]->bounds);
}
CCL_NAMESPACE_END
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