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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_build.h"
#include "bvh_node.h"
#include "bvh_params.h"
#include "bvh_sort.h"
#include "mesh.h"
#include "object.h"
#include "scene.h"
#include "util_algorithm.h"
#include "util_foreach.h"
#include "util_progress.h"
#include "util_time.h"
CCL_NAMESPACE_BEGIN
/* Constructor / Destructor */
BVHBuild::BVHBuild(const vector<Object*>& objects_,
vector<int>& prim_index_, vector<int>& prim_object_,
const BVHParams& params_, Progress& progress_)
: objects(objects_),
prim_index(prim_index_),
prim_object(prim_object_),
params(params_),
progress(progress_),
progress_start_time(0.0)
{
spatial_min_overlap = 0.0f;
progress_num_duplicates = 0;
}
BVHBuild::~BVHBuild()
{
}
/* Adding References */
void BVHBuild::add_reference_mesh(NodeSpec& root, Mesh *mesh, int i)
{
for(uint j = 0; j < mesh->triangles.size(); j++) {
Mesh::Triangle t = mesh->triangles[j];
Reference ref;
ref.prim_index = j;
ref.prim_object = i;
for(int k = 0; k < 3; k++) {
float3 pt = mesh->verts[t.v[k]];
ref.bounds.grow(pt);
}
references.push_back(ref);
root.bounds.grow(ref.bounds);
}
}
void BVHBuild::add_reference_object(NodeSpec& root, Object *ob, int i)
{
Reference ref;
ref.prim_index = -1;
ref.prim_object = i;
ref.bounds = ob->bounds;
references.push_back(ref);
root.bounds.grow(ref.bounds);
}
void BVHBuild::add_references(NodeSpec& root)
{
/* init root spec */
root.num = 0;
root.bounds = BoundBox();
/* add objects */
int i = 0;
foreach(Object *ob, objects) {
if(params.top_level) {
if(ob->mesh->transform_applied)
add_reference_mesh(root, ob->mesh, i);
else
add_reference_object(root, ob, i);
}
else
add_reference_mesh(root, ob->mesh, i);
i++;
if(progress.get_cancel()) return;
}
/* happens mostly on empty meshes */
if(!root.bounds.valid())
root.bounds.grow(make_float3(0.0f, 0.0f, 0.0f));
root.num = references.size();
}
/* Build */
BVHNode* BVHBuild::run()
{
NodeSpec 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.area() * params.spatial_split_alpha;
spatial_right_bounds.clear();
spatial_right_bounds.resize(max(root.num, (int)BVHParams::NUM_SPATIAL_BINS) - 1);
/* init progress updates */
progress_num_duplicates = 0;
progress_start_time = time_dt();
/* build recursively */
return build_node(root, 0, 0.0f, 1.0f);
}
void BVHBuild::progress_update(float progress_start, float progress_end)
{
if(time_dt() - progress_start_time < 0.25f)
return;
float duplicates = (float)progress_num_duplicates/(float)references.size();
string msg = string_printf("Building BVH %.0f%%, duplicates %.0f%%",
progress_start*100.0f, duplicates*100.0f);
progress.set_substatus(msg);
progress_start_time = time_dt();
}
BVHNode* BVHBuild::build_node(const NodeSpec& spec, int level, float progress_start, float progress_end)
{
/* progress update */
progress_update(progress_start, progress_end);
if(progress.get_cancel()) return NULL;
/* small enough or too deep => create leaf. */
if(spec.num <= params.min_leaf_size || level >= BVHParams::MAX_DEPTH)
return create_leaf_node(spec);
/* find split candidates. */
float area = spec.bounds.area();
float leafSAH = area * params.triangle_cost(spec.num);
float nodeSAH = area * params.node_cost(2);
ObjectSplit object = find_object_split(spec, nodeSAH);
SpatialSplit spatial;
if(params.use_spatial_split && level < BVHParams::MAX_SPATIAL_DEPTH) {
BoundBox overlap = object.left_bounds;
overlap.intersect(object.right_bounds);
if(overlap.area() >= spatial_min_overlap)
spatial = find_spatial_split(spec, nodeSAH);
}
/* leaf SAH is the lowest => create leaf. */
float minSAH = min(min(leafSAH, object.sah), spatial.sah);
if(minSAH == leafSAH && spec.num <= params.max_leaf_size)
return create_leaf_node(spec);
/* perform split. */
NodeSpec left, right;
if(params.use_spatial_split && minSAH == spatial.sah)
do_spatial_split(left, right, spec, spatial);
if(!left.num || !right.num)
do_object_split(left, right, spec, object);
/* create inner node. */
progress_num_duplicates += left.num + right.num - spec.num;
float progress_mid = lerp(progress_start, progress_end, (float)right.num / (float)(left.num + right.num));
BVHNode* rightNode = build_node(right, level + 1, progress_start, progress_mid);
if(progress.get_cancel()) {
if(rightNode) rightNode->deleteSubtree();
return NULL;
}
BVHNode* leftNode = build_node(left, level + 1, progress_mid, progress_end);
if(progress.get_cancel()) {
if(leftNode) leftNode->deleteSubtree();
return NULL;
}
return new InnerNode(spec.bounds, leftNode, rightNode);
}
BVHNode *BVHBuild::create_object_leaf_nodes(const Reference *ref, int num)
{
if(num == 0) {
BoundBox bounds;
return new LeafNode(bounds, 0, 0);
}
else if(num == 1) {
prim_index.push_back(ref[0].prim_index);
prim_object.push_back(ref[0].prim_object);
return new LeafNode(ref[0].bounds, prim_index.size()-1, prim_index.size());
}
else {
int mid = num/2;
BVHNode *leaf0 = create_object_leaf_nodes(ref, mid);
BVHNode *leaf1 = create_object_leaf_nodes(ref+mid, num-mid);
BoundBox bounds;
bounds.grow(leaf0->m_bounds);
bounds.grow(leaf1->m_bounds);
return new InnerNode(bounds, leaf0, leaf1);
}
}
BVHNode* BVHBuild::create_leaf_node(const NodeSpec& spec)
{
vector<int>& p_index = prim_index;
vector<int>& p_object = prim_object;
BoundBox bounds;
int num = 0;
for(int i = 0; i < spec.num; i++) {
if(references.back().prim_index != -1) {
p_index.push_back(references.back().prim_index);
p_object.push_back(references.back().prim_object);
bounds.grow(references.back().bounds);
references.pop_back();
num++;
}
}
BVHNode *leaf = NULL;
if(num > 0) {
leaf = new LeafNode(bounds, p_index.size() - num, p_index.size());
if(num == spec.num)
return leaf;
}
/* while there may be multiple triangles in a leaf, for object primitives
* we want them to be the only one, so we */
int ob_num = spec.num - num;
BVHNode *oleaf = create_object_leaf_nodes(&references.back() - (ob_num - 1), ob_num);
for(int i = 0; i < ob_num; i++)
references.pop_back();
if(leaf)
return new InnerNode(spec.bounds, leaf, oleaf);
else
return oleaf;
}
/* Object Split */
BVHBuild::ObjectSplit BVHBuild::find_object_split(const NodeSpec& spec, float nodeSAH)
{
ObjectSplit split;
const Reference *ref_ptr = &references[references.size() - spec.num];
for(int dim = 0; dim < 3; dim++) {
/* sort references */
bvh_reference_sort(references.size() - spec.num, references.size(), &references[0], dim);
/* sweep right to left and determine bounds. */
BoundBox right_bounds;
for(int i = spec.num - 1; i > 0; i--) {
right_bounds.grow(ref_ptr[i].bounds);
spatial_right_bounds[i - 1] = right_bounds;
}
/* sweep left to right and select lowest SAH. */
BoundBox left_bounds;
for(int i = 1; i < spec.num; i++) {
left_bounds.grow(ref_ptr[i - 1].bounds);
right_bounds = spatial_right_bounds[i - 1];
float sah = nodeSAH +
left_bounds.area() * params.triangle_cost(i) +
right_bounds.area() * params.triangle_cost(spec.num - i);
if(sah < split.sah) {
split.sah = sah;
split.dim = dim;
split.num_left = i;
split.left_bounds = left_bounds;
split.right_bounds = right_bounds;
}
}
}
return split;
}
void BVHBuild::do_object_split(NodeSpec& left, NodeSpec& right, const NodeSpec& spec, const ObjectSplit& split)
{
/* sort references according to split */
int start = references.size() - spec.num;
int end = references.size(); /* todo: is this right? */
bvh_reference_sort(start, end, &references[0], split.dim);
/* split node specs */
left.num = split.num_left;
left.bounds = split.left_bounds;
right.num = spec.num - split.num_left;
right.bounds = split.right_bounds;
}
/* Spatial Split */
BVHBuild::SpatialSplit BVHBuild::find_spatial_split(const NodeSpec& spec, float nodeSAH)
{
/* initialize bins. */
float3 origin = spec.bounds.min;
float3 binSize = (spec.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++) {
SpatialBin& bin = spatial_bins[dim][i];
bin.bounds = BoundBox();
bin.enter = 0;
bin.exit = 0;
}
}
/* chop references into bins. */
for(unsigned int refIdx = references.size() - spec.num; refIdx < references.size(); refIdx++) {
const Reference& ref = references[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++) {
Reference currRef = ref;
for(int i = firstBin[dim]; i < lastBin[dim]; i++) {
Reference leftRef, rightRef;
split_reference(leftRef, rightRef, currRef, dim, origin[dim] + binSize[dim] * (float)(i + 1));
spatial_bins[dim][i].bounds.grow(leftRef.bounds);
currRef = rightRef;
}
spatial_bins[dim][lastBin[dim]].bounds.grow(currRef.bounds);
spatial_bins[dim][firstBin[dim]].enter++;
spatial_bins[dim][lastBin[dim]].exit++;
}
}
/* select best split plane. */
SpatialSplit split;
for(int dim = 0; dim < 3; dim++) {
/* sweep right to left and determine bounds. */
BoundBox right_bounds;
for(int i = BVHParams::NUM_SPATIAL_BINS - 1; i > 0; i--) {
right_bounds.grow(spatial_bins[dim][i].bounds);
spatial_right_bounds[i - 1] = right_bounds;
}
/* sweep left to right and select lowest SAH. */
BoundBox left_bounds;
int leftNum = 0;
int rightNum = spec.num;
for(int i = 1; i < BVHParams::NUM_SPATIAL_BINS; i++) {
left_bounds.grow(spatial_bins[dim][i - 1].bounds);
leftNum += spatial_bins[dim][i - 1].enter;
rightNum -= spatial_bins[dim][i - 1].exit;
float sah = nodeSAH +
left_bounds.area() * params.triangle_cost(leftNum) +
spatial_right_bounds[i - 1].area() * params.triangle_cost(rightNum);
if(sah < split.sah) {
split.sah = sah;
split.dim = dim;
split.pos = origin[dim] + binSize[dim] * (float)i;
}
}
}
return split;
}
void BVHBuild::do_spatial_split(NodeSpec& left, NodeSpec& right, const NodeSpec& spec, const SpatialSplit& split)
{
/* 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<Reference>& refs = references;
int left_start = refs.size() - spec.num;
int left_end = left_start;
int right_start = refs.size();
left.bounds = right.bounds = BoundBox();
for(int i = left_end; i < right_start; i++) {
if(refs[i].bounds.max[split.dim] <= split.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[split.dim] >= split.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. */
while(left_end < right_start) {
/* split reference. */
Reference lref, rref;
split_reference(lref, rref, refs[left_end], split.dim, split.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 = params.triangle_cost(left_end - left_start);
float rac = params.triangle_cost(refs.size() - right_start);
float lbc = params.triangle_cost(left_end - left_start + 1);
float rbc = params.triangle_cost(refs.size() - right_start + 1);
float unsplitLeftSAH = lub.area() * lbc + right.bounds.area() * rac;
float unsplitRightSAH = left.bounds.area() * lac + rub.area() * rbc;
float duplicateSAH = ldb.area() * lbc + rdb.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;
refs.push_back(rref);
}
}
left.num = left_end - left_start;
right.num = refs.size() - right_start;
}
void BVHBuild::split_reference(Reference& left, Reference& right, const Reference& ref, int dim, float pos)
{
/* initialize references. */
left.prim_index = right.prim_index = ref.prim_index;
left.prim_object = right.prim_object = ref.prim_object;
left.bounds = right.bounds = BoundBox();
/* loop over vertices/edges. */
Object *ob = objects[ref.prim_object];
const Mesh *mesh = ob->mesh;
const int *inds = mesh->triangles[ref.prim_index].v;
const float3 *verts = &mesh->verts[0];
const float3* v1 = &verts[inds[2]];
for(int i = 0; i < 3; i++) {
const float3* v0 = v1;
int vindex = inds[i];
v1 = &verts[vindex];
float v0p = (*v0)[dim];
float v1p = (*v1)[dim];
/* insert vertex to the boxes it belongs to. */
if(v0p <= pos)
left.bounds.grow(*v0);
if(v0p >= pos)
right.bounds.grow(*v0);
/* edge intersects the plane => insert intersection to both boxes. */
if((v0p < pos && v1p > pos) || (v0p > pos && v1p < pos)) {
float3 t = lerp(*v0, *v1, clamp((pos - v0p) / (v1p - v0p), 0.0f, 1.0f));
left.bounds.grow(t);
right.bounds.grow(t);
}
}
/* intersect with original bounds. */
left.bounds.max[dim] = pos;
right.bounds.min[dim] = pos;
left.bounds.intersect(ref.bounds);
right.bounds.intersect(ref.bounds);
}
CCL_NAMESPACE_END
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