bvh.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 "mesh.h"
#include "object.h"
#include "scene.h"

#include "bvh.h"
#include "bvh_build.h"
#include "bvh_node.h"
#include "bvh_params.h"

#include "util_cache.h"
#include "util_debug.h"
#include "util_foreach.h"
#include "util_map.h"
#include "util_progress.h"
#include "util_types.h"

CCL_NAMESPACE_BEGIN

/* Pack Utility */

struct BVHStackEntry
{
    const BVHNode *node;
    int idx;

    BVHStackEntry(const BVHNode* n = 0, int i = 0)
    : node(n), idx(i)
    {
    }

    int encodeIdx() const
    {
        return (node->is_leaf())? ~idx: idx;
    }
};

/* BVH */

BVH::BVH(const BVHParams& params_, const vector<Object*>& objects_)
: params(params_), objects(objects_)
{
}

BVH *BVH::create(const BVHParams& params, const vector<Object*>& objects)
{
    if(params.use_qbvh)
        return new QBVH(params, objects);
    else
        return new RegularBVH(params, objects);
}

/* Cache */

bool BVH::cache_read(CacheData& key)
{
    key.add(&params, sizeof(params));

    foreach(Object *ob, objects) {
        key.add(ob->mesh->verts);
        key.add(ob->mesh->triangles);
        key.add(&ob->bounds, sizeof(ob->bounds));
        key.add(&ob->visibility, sizeof(ob->visibility));
        key.add(&ob->mesh->transform_applied, sizeof(bool));
    }

    CacheData value;

    if(Cache::global.lookup(key, value)) {
        cache_filename = key.get_filename();

        value.read(pack.root_index);
        value.read(pack.SAH);

        value.read(pack.nodes);
        value.read(pack.object_node);
        value.read(pack.tri_woop);
        value.read(pack.prim_visibility);
        value.read(pack.prim_index);
        value.read(pack.prim_object);
        value.read(pack.is_leaf);

        return true;
    }

    return false;
}

void BVH::cache_write(CacheData& key)
{
    CacheData value;

    value.add(pack.root_index);
    value.add(pack.SAH);

    value.add(pack.nodes);
    value.add(pack.object_node);
    value.add(pack.tri_woop);
    value.add(pack.prim_visibility);
    value.add(pack.prim_index);
    value.add(pack.prim_object);
    value.add(pack.is_leaf);

    Cache::global.insert(key, value);

    cache_filename = key.get_filename();
}

void BVH::clear_cache_except()
{
    set<string> except;

    if(!cache_filename.empty())
        except.insert(cache_filename);

    foreach(Object *ob, objects) {
        Mesh *mesh = ob->mesh;
        BVH *bvh = mesh->bvh;

        if(bvh && !bvh->cache_filename.empty())
            except.insert(bvh->cache_filename);
    }

    Cache::global.clear_except("bvh", except);
}

/* Building */

void BVH::build(Progress& progress)
{
    progress.set_substatus("Building BVH");

    /* cache read */
    CacheData key("bvh");

    if(params.use_cache) {
        progress.set_substatus("Looking in BVH cache");

        if(cache_read(key))
            return;
    }

    /* build nodes */
    vector<int> prim_index;
    vector<int> prim_object;

    BVHBuild bvh_build(objects, prim_index, prim_object, params, progress);
    BVHNode *root = bvh_build.run();

    if(progress.get_cancel()) {
        if(root) root->deleteSubtree();
        return;
    }

    /* todo: get rid of this copy */
    pack.prim_index = prim_index;
    pack.prim_object = prim_object;

    /* compute SAH */
    if(!params.top_level)
        pack.SAH = root->computeSubtreeSAHCost(params);

    if(progress.get_cancel()) {
        root->deleteSubtree();
        return;
    }

    /* pack triangles */
    progress.set_substatus("Packing BVH triangles");
    pack_triangles();

    if(progress.get_cancel()) {
        root->deleteSubtree();
        return;
    }

    /* pack nodes */
    progress.set_substatus("Packing BVH nodes");
    array<int> tmp_prim_object = pack.prim_object;
    pack_nodes(tmp_prim_object, root);
    
    /* free build nodes */
    root->deleteSubtree();

    if(progress.get_cancel()) return;

    /* cache write */
    if(params.use_cache) {
        progress.set_substatus("Writing BVH cache");
        cache_write(key);

        /* clear other bvh files from cache */
        if(params.top_level)
            clear_cache_except();
    }
}

/* Refitting */

void BVH::refit(Progress& progress)
{
    progress.set_substatus("Packing BVH triangles");
    pack_triangles();

    if(progress.get_cancel()) return;

    progress.set_substatus("Refitting BVH nodes");
    refit_nodes();
}

/* Triangles */

void BVH::pack_triangle(int idx, float4 woop[3])
{
    /* create Woop triangle */
    int tob = pack.prim_object[idx];
    const Mesh *mesh = objects[tob]->mesh;
    int tidx = pack.prim_index[idx];
    const int *vidx = mesh->triangles[tidx].v;
    const float3* vpos = &mesh->verts[0];
    float3 v0 = vpos[vidx[0]];
    float3 v1 = vpos[vidx[1]];
    float3 v2 = vpos[vidx[2]];

    float3 r0 = v0 - v2;
    float3 r1 = v1 - v2;
    float3 r2 = cross(r0, r1);

    if(dot(r0, r0) == 0.0f || dot(r1, r1) == 0.0f || dot(r2, r2) == 0.0f) {
        /* degenerate */
        woop[0] = make_float4(0.0f, 0.0f, 0.0f, 0.0f);
        woop[1] = make_float4(0.0f, 0.0f, 0.0f, 0.0f);
        woop[2] = make_float4(0.0f, 0.0f, 0.0f, 0.0f);
    }
    else {
        Transform t = make_transform(
            r0.x, r1.x, r2.x, v2.x,
            r0.y, r1.y, r2.y, v2.y,
            r0.z, r1.z, r2.z, v2.z,
            0.0f, 0.0f, 0.0f, 1.0f);

        t = transform_inverse(t);

        woop[0] = make_float4(t.z.x, t.z.y, t.z.z, -t.z.w);
        woop[1] = make_float4(t.x.x, t.x.y, t.x.z, t.x.w);
        woop[2] = make_float4(t.y.x, t.y.y, t.y.z, t.y.w);
    }
}

void BVH::pack_triangles()
{
    int nsize = TRI_NODE_SIZE;
    size_t tidx_size = pack.prim_index.size();

    pack.tri_woop.clear();
    pack.tri_woop.resize(tidx_size * nsize);
    pack.prim_visibility.clear();
    pack.prim_visibility.resize(tidx_size);

    for(unsigned int i = 0; i < tidx_size; i++) {
        if(pack.prim_index[i] != -1) {
            float4 woop[3];

            pack_triangle(i, woop);
            memcpy(&pack.tri_woop[i * nsize], woop, sizeof(float4)*3);

            int tob = pack.prim_object[i];
            Object *ob = objects[tob];
            pack.prim_visibility[i] = ob->visibility;
        }
    }
}

/* Pack Instances */

void BVH::pack_instances(size_t nodes_size)
{
    /* The BVH's for instances are built separately, but for traversal all
       BVH's are stored in global arrays. This function merges them into the
       top level BVH, adjusting indexes and offsets where appropriate. */
    bool use_qbvh = params.use_qbvh;
    size_t nsize = (use_qbvh)? BVH_QNODE_SIZE: BVH_NODE_SIZE;

    /* adjust primitive index to point to the triangle in the global array, for
       meshes with transform applied and already in the top level BVH */
    for(size_t i = 0; i < pack.prim_index.size(); i++)
        if(pack.prim_index[i] != -1)
            pack.prim_index[i] += objects[pack.prim_object[i]]->mesh->tri_offset;

    /* track offsets of instanced BVH data in global array */
    size_t tri_offset = pack.prim_index.size();
    size_t nodes_offset = nodes_size;

    /* clear array that gives the node indexes for instanced objects */
    pack.object_node.clear();

    /* reserve */
    size_t prim_index_size = pack.prim_index.size();
    size_t tri_woop_size = pack.tri_woop.size();

    size_t pack_prim_index_offset = prim_index_size;
    size_t pack_tri_woop_offset = tri_woop_size;
    size_t pack_nodes_offset = nodes_size;
    size_t object_offset = 0;

    map<Mesh*, int> mesh_map;

    foreach(Object *ob, objects) {
        Mesh *mesh = ob->mesh;
        BVH *bvh = mesh->bvh;

        if(!mesh->transform_applied) {
            if(mesh_map.find(mesh) == mesh_map.end()) {
                prim_index_size += bvh->pack.prim_index.size();
                tri_woop_size += bvh->pack.tri_woop.size();
                nodes_size += bvh->pack.nodes.size()*nsize;

                mesh_map[mesh] = 1;
            }
        }
    }

    mesh_map.clear();

    pack.prim_index.resize(prim_index_size);
    pack.prim_object.resize(prim_index_size);
    pack.prim_visibility.resize(prim_index_size);
    pack.tri_woop.resize(tri_woop_size);
    pack.nodes.resize(nodes_size);
    pack.object_node.resize(objects.size());

    int *pack_prim_index = (pack.prim_index.size())? &pack.prim_index[0]: NULL;
    int *pack_prim_object = (pack.prim_object.size())? &pack.prim_object[0]: NULL;
    uint *pack_prim_visibility = (pack.prim_visibility.size())? &pack.prim_visibility[0]: NULL;
    float4 *pack_tri_woop = (pack.tri_woop.size())? &pack.tri_woop[0]: NULL;
    int4 *pack_nodes = (pack.nodes.size())? &pack.nodes[0]: NULL;

    /* merge */
    foreach(Object *ob, objects) {
        Mesh *mesh = ob->mesh;

        /* if mesh transform is applied, that means it's already in the top
           level BVH, and we don't need to merge it in */
        if(mesh->transform_applied) {
            pack.object_node[object_offset++] = 0;
            continue;
        }

        /* if mesh already added once, don't add it again, but used set
           node offset for this object */
        map<Mesh*, int>::iterator it = mesh_map.find(mesh);

        if(mesh_map.find(mesh) != mesh_map.end()) {
            int noffset = it->second;
            pack.object_node[object_offset++] = noffset;
            continue;
        }

        BVH *bvh = mesh->bvh;

        int noffset = nodes_offset/nsize;
        int mesh_tri_offset = mesh->tri_offset;

        /* fill in node indexes for instances */
        if(bvh->pack.is_leaf[0])
            pack.object_node[object_offset++] = -noffset-1;
        else
            pack.object_node[object_offset++] = noffset;

        mesh_map[mesh] = pack.object_node[object_offset-1];

        /* merge primitive and object indexes */
        if(bvh->pack.prim_index.size()) {
            size_t bvh_prim_index_size = bvh->pack.prim_index.size();
            int *bvh_prim_index = &bvh->pack.prim_index[0];
            uint *bvh_prim_visibility = &bvh->pack.prim_visibility[0];

            for(size_t i = 0; i < bvh_prim_index_size; i++) {
                pack_prim_index[pack_prim_index_offset] = bvh_prim_index[i] + mesh_tri_offset;
                pack_prim_visibility[pack_prim_index_offset] = bvh_prim_visibility[i];
                pack_prim_object[pack_prim_index_offset] = 0;  // unused for instances
                pack_prim_index_offset++;
            }
        }

        /* merge triangle intersection data */
        if(bvh->pack.tri_woop.size()) {
            memcpy(pack_tri_woop+pack_tri_woop_offset, &bvh->pack.tri_woop[0],
                bvh->pack.tri_woop.size()*sizeof(float4));
            pack_tri_woop_offset += bvh->pack.tri_woop.size();
        }

        /* merge nodes */
        if( bvh->pack.nodes.size()) {
            size_t nsize_bbox = (use_qbvh)? nsize-2: nsize-1;
            int4 *bvh_nodes = &bvh->pack.nodes[0];
            size_t bvh_nodes_size = bvh->pack.nodes.size(); 
            int *bvh_is_leaf = &bvh->pack.is_leaf[0];

            for(size_t i = 0, j = 0; i < bvh_nodes_size; i+=nsize, j++) {
                memcpy(pack_nodes + pack_nodes_offset, bvh_nodes + i, nsize_bbox*sizeof(int4));

                /* modify offsets into arrays */
                int4 data = bvh_nodes[i + nsize_bbox];

                if(bvh_is_leaf[j]) {
                    data.x += tri_offset;
                    data.y += tri_offset;
                }
                else {
                    data.x += (data.x < 0)? -noffset: noffset;
                    data.y += (data.y < 0)? -noffset: noffset;

                    if(use_qbvh) {
                        data.z += (data.z < 0)? -noffset: noffset;
                        data.w += (data.w < 0)? -noffset: noffset;
                    }
                }

                pack_nodes[pack_nodes_offset + nsize_bbox] = data;

                if(use_qbvh)
                    pack_nodes[pack_nodes_offset + nsize_bbox+1] = bvh_nodes[i + nsize_bbox+1];

                pack_nodes_offset += nsize;
            }
        }

        nodes_offset += bvh->pack.nodes.size();
        tri_offset += bvh->pack.prim_index.size();
    }
}

/* Regular BVH */

RegularBVH::RegularBVH(const BVHParams& params_, const vector<Object*>& objects_)
: BVH(params_, objects_)
{
}

void RegularBVH::pack_leaf(const BVHStackEntry& e, const LeafNode *leaf)
{
    if(leaf->num_triangles() == 1 && pack.prim_index[leaf->m_lo] == -1)
        /* object */
        pack_node(e.idx, leaf->m_bounds, leaf->m_bounds, ~(leaf->m_lo), 0, leaf->m_visibility, leaf->m_visibility);
    else
        /* triangle */
        pack_node(e.idx, leaf->m_bounds, leaf->m_bounds, leaf->m_lo, leaf->m_hi, leaf->m_visibility, leaf->m_visibility);
}

void RegularBVH::pack_inner(const BVHStackEntry& e, const BVHStackEntry& e0, const BVHStackEntry& e1)
{
    pack_node(e.idx, e0.node->m_bounds, e1.node->m_bounds, e0.encodeIdx(), e1.encodeIdx(), e0.node->m_visibility, e1.node->m_visibility);
}

void RegularBVH::pack_node(int idx, const BoundBox& b0, const BoundBox& b1, int c0, int c1, uint visibility0, uint visibility1)
{
    int4 data[BVH_NODE_SIZE] =
    {
        make_int4(__float_as_int(b0.min.x), __float_as_int(b0.max.x), __float_as_int(b0.min.y), __float_as_int(b0.max.y)),
        make_int4(__float_as_int(b1.min.x), __float_as_int(b1.max.x), __float_as_int(b1.min.y), __float_as_int(b1.max.y)),
        make_int4(__float_as_int(b0.min.z), __float_as_int(b0.max.z), __float_as_int(b1.min.z), __float_as_int(b1.max.z)),
        make_int4(c0, c1, visibility0, visibility1)
    };

    memcpy(&pack.nodes[idx * BVH_NODE_SIZE], data, sizeof(int4)*BVH_NODE_SIZE);
}

void RegularBVH::pack_nodes(const array<int>& prims, const BVHNode *root)
{
    size_t node_size = root->getSubtreeSize(BVH_STAT_NODE_COUNT);

    /* resize arrays */
    pack.nodes.clear();
    pack.is_leaf.clear();
    pack.is_leaf.resize(node_size);

    /* for top level BVH, first merge existing BVH's so we know the offsets */
    if(params.top_level)
        pack_instances(node_size*BVH_NODE_SIZE);
    else
        pack.nodes.resize(node_size*BVH_NODE_SIZE);

    int nextNodeIdx = 0;

    vector<BVHStackEntry> stack;
    stack.push_back(BVHStackEntry(root, nextNodeIdx++));

    while(stack.size()) {
        BVHStackEntry e = stack.back();
        stack.pop_back();

        pack.is_leaf[e.idx] = e.node->is_leaf();

        if(e.node->is_leaf()) {
            /* leaf node */
            const LeafNode* leaf = reinterpret_cast<const LeafNode*>(e.node);
            pack_leaf(e, leaf);
        }
        else {
            /* innner node */
            stack.push_back(BVHStackEntry(e.node->get_child(0), nextNodeIdx++));
            stack.push_back(BVHStackEntry(e.node->get_child(1), nextNodeIdx++));

            pack_inner(e, stack[stack.size()-2], stack[stack.size()-1]);
        }
    }

    /* root index to start traversal at, to handle case of single leaf node */
    pack.root_index = (pack.is_leaf[0])? -1: 0;
}

void RegularBVH::refit_nodes()
{
    assert(!params.top_level);

    BoundBox bbox;
    uint visibility = 0;
    refit_node(0, (pack.is_leaf[0])? true: false, bbox, visibility);
}

void RegularBVH::refit_node(int idx, bool leaf, BoundBox& bbox, uint& visibility)
{
    int4 *data = &pack.nodes[idx*4];

    int c0 = data[3].x;
    int c1 = data[3].y;

    if(leaf) {
        /* refit leaf node */
        for(int tri = c0; tri < c1; tri++) {
            int tidx = pack.prim_index[tri];
            int tob = pack.prim_object[tri];
            Object *ob = objects[tob];

            if(tidx == -1) {
                /* object instance */
                bbox.grow(ob->bounds);
            }
            else {
                /* triangles */
                const Mesh *mesh = ob->mesh;
                int tri_offset = (params.top_level)? mesh->tri_offset: 0;
                const int *vidx = mesh->triangles[tidx - tri_offset].v;
                const float3 *vpos = &mesh->verts[0];

                bbox.grow(vpos[vidx[0]]);
                bbox.grow(vpos[vidx[1]]);
                bbox.grow(vpos[vidx[2]]);
            }

            visibility |= ob->visibility;
        }

        pack_node(idx, bbox, bbox, c0, c1, visibility, visibility);
    }
    else {
        /* refit inner node, set bbox from children */
        BoundBox bbox0, bbox1;
        uint visibility0 = 0, visibility1 = 0;

        refit_node((c0 < 0)? -c0-1: c0, (c0 < 0), bbox0, visibility0);
        refit_node((c1 < 0)? -c1-1: c1, (c1 < 0), bbox1, visibility1);

        pack_node(idx, bbox0, bbox1, c0, c1, visibility0, visibility1);

        bbox.grow(bbox0);
        bbox.grow(bbox1);
        visibility = visibility0|visibility1;
    }
}

/* QBVH */

QBVH::QBVH(const BVHParams& params_, const vector<Object*>& objects_)
: BVH(params_, objects_)
{
    params.use_qbvh = true;

    /* todo: use visibility */
}

void QBVH::pack_leaf(const BVHStackEntry& e, const LeafNode *leaf)
{
    float4 data[BVH_QNODE_SIZE];

    memset(data, 0, sizeof(data));

    if(leaf->num_triangles() == 1 && pack.prim_index[leaf->m_lo] == -1) {
        /* object */
        data[6].x = __int_as_float(~(leaf->m_lo));
        data[6].y = __int_as_float(0);
    }
    else {
        /* triangle */
        data[6].x = __int_as_float(leaf->m_lo);
        data[6].y = __int_as_float(leaf->m_hi);
    }

    memcpy(&pack.nodes[e.idx * BVH_QNODE_SIZE], data, sizeof(float4)*BVH_QNODE_SIZE);
}

void QBVH::pack_inner(const BVHStackEntry& e, const BVHStackEntry *en, int num)
{
    float4 data[BVH_QNODE_SIZE];

    for(int i = 0; i < num; i++) {
        float3 bb_min = en[i].node->m_bounds.min;
        float3 bb_max = en[i].node->m_bounds.max;

        data[0][i] = bb_min.x;
        data[1][i] = bb_max.x;
        data[2][i] = bb_min.y;
        data[3][i] = bb_max.y;
        data[4][i] = bb_min.z;
        data[5][i] = bb_max.z;

        data[6][i] = __int_as_float(en[i].encodeIdx());
        data[7][i] = 0.0f;
    }

    for(int i = num; i < 4; i++) {
        data[0][i] = 0.0f;
        data[1][i] = 0.0f;
        data[2][i] = 0.0f;

        data[3][i] = 0.0f;
        data[4][i] = 0.0f;
        data[5][i] = 0.0f;

        data[6][i] = __int_as_float(0);
        data[7][i] = 0.0f;
    }

    memcpy(&pack.nodes[e.idx * BVH_QNODE_SIZE], data, sizeof(float4)*BVH_QNODE_SIZE);
}

/* Quad SIMD Nodes */

void QBVH::pack_nodes(const array<int>& prims, const BVHNode *root)
{
    size_t node_size = root->getSubtreeSize(BVH_STAT_NODE_COUNT);

    /* resize arrays */
    pack.nodes.clear();
    pack.is_leaf.clear();
    pack.is_leaf.resize(node_size);

    /* for top level BVH, first merge existing BVH's so we know the offsets */
    if(params.top_level)
        pack_instances(node_size*BVH_QNODE_SIZE);
    else
        pack.nodes.resize(node_size*BVH_QNODE_SIZE);

    int nextNodeIdx = 0;

    vector<BVHStackEntry> stack;
    stack.push_back(BVHStackEntry(root, nextNodeIdx++));

    while(stack.size()) {
        BVHStackEntry e = stack.back();
        stack.pop_back();

        pack.is_leaf[e.idx] = e.node->is_leaf();

        if(e.node->is_leaf()) {
            /* leaf node */
            const LeafNode* leaf = reinterpret_cast<const LeafNode*>(e.node);
            pack_leaf(e, leaf);
        }
        else {
            /* inner node */
            const BVHNode *node = e.node;
            const BVHNode *node0 = node->get_child(0);
            const BVHNode *node1 = node->get_child(1);

            /* collect nodes */
            const BVHNode *nodes[4];
            int numnodes = 0;

            if(node0->is_leaf()) {
                nodes[numnodes++] = node0;
            }
            else {
                nodes[numnodes++] = node0->get_child(0);
                nodes[numnodes++] = node0->get_child(1);
            }

            if(node1->is_leaf()) {
                nodes[numnodes++] = node1;
            }
            else {
                nodes[numnodes++] = node1->get_child(0);
                nodes[numnodes++] = node1->get_child(1);
            }

            /* push entries on the stack */
            for(int i = 0; i < numnodes; i++)
                stack.push_back(BVHStackEntry(nodes[i], nextNodeIdx++));

            /* set node */
            pack_inner(e, &stack[stack.size()-numnodes], numnodes);
        }
    }

    /* root index to start traversal at, to handle case of single leaf node */
    pack.root_index = (pack.is_leaf[0])? -1: 0;
}

void QBVH::refit_nodes()
{
    assert(0); /* todo */
}

CCL_NAMESPACE_END