reorganize.h

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/*
 * ***** BEGIN GPL LICENSE BLOCK *****
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version. 
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 *
 * The Original Code is Copyright (C) 2009 Blender Foundation.
 * All rights reserved.
 *
 * The Original Code is: all of this file.
 *
 * Contributor(s): André Pinto.
 *
 * ***** END GPL LICENSE BLOCK *****
 */

#include <float.h>
#include <math.h>
#include <stdio.h>

#include <algorithm>
#include <queue>
#include <vector>

#include "BKE_global.h"

#ifdef _WIN32
#  ifdef INFINITY
#    undef INFINITY
#  endif
#  define INFINITY FLT_MAX // in mingw math.h: (1.0F/0.0F). This generates compile error, though.
#endif

extern int tot_pushup;
extern int tot_pushdown;

#if !defined(INFINITY) && defined(HUGE_VAL)
#define INFINITY HUGE_VAL
#endif

template<class Node>
bool node_fits_inside(Node *a, Node *b)
{
    return bb_fits_inside(b->bb, b->bb+3, a->bb, a->bb+3);
}

template<class Node>
void reorganize_find_fittest_parent(Node *tree, Node *node, std::pair<float,Node*> &cost)
{
    std::queue<Node*> q;
    q.push(tree);
    
    while(!q.empty())
    {
        Node *parent = q.front();
        q.pop();
        
        if(parent == node) continue;
        if(node_fits_inside(node, parent) && RE_rayobject_isAligned(parent->child) )
        {
            float pcost = bb_area(parent->bb, parent->bb+3);
            cost = std::min( cost, std::make_pair(pcost,parent) );
            for(Node *child = parent->child; child; child = child->sibling)
                q.push(child);          
        }
    }
}

static int tot_moves = 0;
template<class Node>
void reorganize(Node *root)
{
    std::queue<Node*> q;

    q.push(root);
    while(!q.empty())
    {
        Node * node = q.front();
        q.pop();
        
        if( RE_rayobject_isAligned(node->child) )
        {
            for(Node **prev = &node->child; *prev; )
            {
                assert( RE_rayobject_isAligned(*prev) ); 
                q.push(*prev);

                std::pair<float,Node*> best(FLT_MAX, root);
                reorganize_find_fittest_parent( root, *prev, best );

                if(best.second == node)
                {
                    //Already inside the fitnest BB
                    prev = &(*prev)->sibling;
                }
                else
                {
                    Node *tmp = *prev;
                    *prev = (*prev)->sibling;
                    
                    tmp->sibling =  best.second->child;
                    best.second->child = tmp;
                    
                    tot_moves++;
                }
            
            
            }
        }
        if(node != root)
        {
        }
    }
}

/*
 * Prunes useless nodes from trees:
 *  erases nodes with total amount of primitives = 0
 *  prunes nodes with only one child (except if that child is a primitive)
 */
template<class Node>
void remove_useless(Node *node, Node **new_node)
{
    if( RE_rayobject_isAligned(node->child) )
    {

        for(Node **prev = &node->child; *prev; )
        {
            Node *next = (*prev)->sibling;
            remove_useless(*prev, prev);
            if(*prev == 0)
                *prev = next;
            else
            {
                (*prev)->sibling = next;
                prev = &((*prev)->sibling);
            }
        }           
    }
    if(node->child)
    {
        if(RE_rayobject_isAligned(node->child) && node->child->sibling == 0)
            *new_node = node->child;
    }
    else if(node->child == 0)
        *new_node = 0;  
}

/*
 * Minimizes expected number of BBtest by colapsing nodes
 * it uses surface area heuristic for determining whether a node should be colapsed
 */
template<class Node>
void pushup(Node *parent)
{
    if(is_leaf(parent)) return;
    
    float p_area = bb_area(parent->bb, parent->bb+3);
    Node **prev = &parent->child;
    for(Node *child = parent->child; RE_rayobject_isAligned(child) && child; )
    {
        float c_area = bb_area(child->bb, child->bb+3) ;
        int nchilds = count_childs(child);
        float original_cost = ((p_area != 0.0f)? (c_area / p_area)*nchilds: 1.0f) + 1;
        float flatten_cost = nchilds;
        if(flatten_cost < original_cost && nchilds >= 2)
        {
            append_sibling(child, child->child);
            child = child->sibling;
            *prev = child;

//          *prev = child->child;
//          append_sibling( *prev, child->sibling );
//          child = *prev;
            tot_pushup++;
        }
        else
        {
            *prev = child;
            prev = &(*prev)->sibling;
            child = *prev;
        }       
    }
    
    for(Node *child = parent->child; RE_rayobject_isAligned(child) && child; child = child->sibling)
        pushup(child);
}

/*
 * try to optimize number of childs to be a multiple of SSize
 */
template<class Node, int SSize>
void pushup_simd(Node *parent)
{
    if(is_leaf(parent)) return;
    
    int n = count_childs(parent);
        
    Node **prev = &parent->child;
    for(Node *child = parent->child; RE_rayobject_isAligned(child) && child; )
    {
        int cn = count_childs(child);
        if(cn-1 <= (SSize - (n%SSize) ) % SSize && RE_rayobject_isAligned(child->child) )
        {
            n += (cn - 1);
            append_sibling(child, child->child);
            child = child->sibling;
            *prev = child;  
        }
        else
        {
            *prev = child;
            prev = &(*prev)->sibling;
            child = *prev;
        }       
    }
        
    for(Node *child = parent->child; RE_rayobject_isAligned(child) && child; child = child->sibling)
        pushup_simd<Node,SSize>(child);
}


/*
 * Pushdown
 *  makes sure no child fits inside any of its sibling
 */
template<class Node>
void pushdown(Node *parent)
{
    Node **s_child = &parent->child;
    Node * child = parent->child;
    
    while(child && RE_rayobject_isAligned(child))
    {
        Node *next = child->sibling;
        Node **next_s_child = &child->sibling;
        
        //assert(bb_fits_inside(parent->bb, parent->bb+3, child->bb, child->bb+3));
        
        for(Node *i = parent->child; RE_rayobject_isAligned(i) && i; i = i->sibling)
        if(child != i && bb_fits_inside(i->bb, i->bb+3, child->bb, child->bb+3) && RE_rayobject_isAligned(i->child))
        {
//          todo optimize (should the one with the smallest area?)
//          float ia = bb_area(i->bb, i->bb+3)
//          if(child->i)
            *s_child = child->sibling;
            child->sibling = i->child;
            i->child = child;
            next_s_child = s_child;
            
            tot_pushdown++;
            break;
        }
        child = next;
        s_child = next_s_child;
    }
    
    for(Node *i = parent->child; RE_rayobject_isAligned(i) && i; i = i->sibling)
        pushdown( i );  
}


/*
 * BVH refit
 * readjust nodes BB (useful if nodes childs where modified)
 */
template<class Node>
float bvh_refit(Node *node)
{
    if(is_leaf(node)) return 0; 
    if(is_leaf(node->child)) return 0;
    
    float total = 0;
    
    for(Node *child = node->child; child; child = child->sibling)
        total += bvh_refit(child);
        
    float old_area = bb_area(node->bb, node->bb+3);
    INIT_MINMAX(node->bb, node->bb+3);
    for(Node *child = node->child; child; child = child->sibling)
    {
        DO_MIN(child->bb, node->bb);
        DO_MAX(child->bb+3, node->bb+3);
    }
    total += old_area - bb_area(node->bb, node->bb+3);
    return total;
}


/*
 * this finds the best way to packing a tree according to a given test cost function
 * with the purpose to reduce the expected cost (eg.: number of BB tests).
 */
#include <vector>
#define MAX_CUT_SIZE        4               /* svbvh assumes max 4 children! */
#define MAX_OPTIMIZE_CHILDS MAX_CUT_SIZE

struct OVBVHNode
{
    float   bb[6];

    OVBVHNode *child;
    OVBVHNode *sibling;
    
    /*
     * Returns min cost to represent the subtree starting at the given node,
     * allowing it to have a given cutsize
     */
    float cut_cost[MAX_CUT_SIZE];
    float get_cost(int cutsize)
    {
        return cut_cost[cutsize-1];
    }
    
    /*
     * This saves the cut size of this child, when parent is reaching
     * its minimum cut with the given cut size
     */
    int cut_size[MAX_CUT_SIZE];
    int get_cut_size(int parent_cut_size)
    {
        return cut_size[parent_cut_size-1];
    }
    
    /*
     * Reorganize the node based on calculated cut costs
     */  
    int best_cutsize;
    void set_cut(int cutsize, OVBVHNode ***cut)
    {
        if(cutsize == 1)
        {
            **cut = this;
             *cut = &(**cut)->sibling;
        }
        else
        {
            if(cutsize > MAX_CUT_SIZE)
            {
                for(OVBVHNode *child = this->child; child && RE_rayobject_isAligned(child); child = child->sibling)
                {
                    child->set_cut( 1, cut );
                    cutsize--;
                }
                assert(cutsize == 0);
            }
            else
                for(OVBVHNode *child = this->child; child && RE_rayobject_isAligned(child); child = child->sibling)
                    child->set_cut( child->get_cut_size( cutsize ), cut );
        }
    }

    void optimize()
    {
        if(RE_rayobject_isAligned(this->child))
        {
            //Calc new childs
            {
                OVBVHNode **cut = &(this->child);
                set_cut( best_cutsize, &cut );
                *cut = NULL;
            }

            //Optimize new childs
            for(OVBVHNode *child = this->child; child && RE_rayobject_isAligned(child); child = child->sibling)
                child->optimize();
        }       
    }
};

/*
 * Calculates an optimal SIMD packing
 *
 */
template<class Node, class TestCost>
struct VBVH_optimalPackSIMD
{
    TestCost testcost;
    
    VBVH_optimalPackSIMD(TestCost testcost)
    {
        this->testcost = testcost;
    }
    
    /*
     * calc best cut on a node
     */
    struct calc_best
    {
        Node *child[MAX_OPTIMIZE_CHILDS];
        float child_hit_prob[MAX_OPTIMIZE_CHILDS];
        
        calc_best(Node *node)
        {
            int nchilds = 0;
            //Fetch childs and needed data
            {
                float parent_area = bb_area(node->bb, node->bb+3);
                for(Node *child = node->child; child && RE_rayobject_isAligned(child); child = child->sibling)
                {
                    this->child[nchilds] = child;
                    this->child_hit_prob[nchilds] = (parent_area != 0.0f)? bb_area(child->bb, child->bb+3) / parent_area: 1.0f;
                    nchilds++;
                }

                assert(nchilds >= 2 && nchilds <= MAX_OPTIMIZE_CHILDS);
            }
            
            
            //Build DP table to find minimum cost to represent this node with a given cutsize
            int   bt  [MAX_OPTIMIZE_CHILDS+1][MAX_CUT_SIZE+1]; //backtrace table
            float cost[MAX_OPTIMIZE_CHILDS+1][MAX_CUT_SIZE+1]; //cost table (can be reduced to float[2][MAX_CUT_COST])
            
            for(int i=0; i<=nchilds; i++)
            for(int j=0; j<=MAX_CUT_SIZE; j++)
                cost[i][j] = INFINITY;

            cost[0][0] = 0;
            
            for(int i=1; i<=nchilds; i++)
            for(int size=i-1; size/*+(nchilds-i)*/<=MAX_CUT_SIZE; size++)
            for(int cut=1; cut+size/*+(nchilds-i)*/<=MAX_CUT_SIZE; cut++)
            {
                float new_cost = cost[i-1][size] + child_hit_prob[i-1]*child[i-1]->get_cost(cut);
                if(new_cost < cost[i][size+cut])
                {
                    cost[i][size+cut] = new_cost;
                    bt[i][size+cut] = cut;
                }
            }
            
            //Save the ways to archieve the minimum cost with a given cutsize
            for(int i = nchilds; i <= MAX_CUT_SIZE; i++)
            {
                node->cut_cost[i-1] = cost[nchilds][i];
                if(cost[nchilds][i] < INFINITY)
                {
                    int current_size = i;
                    for(int j=nchilds; j>0; j--)
                    {
                        child[j-1]->cut_size[i-1] = bt[j][current_size];
                        current_size -= bt[j][current_size];
                    }
                }
            }           
        }
    };
    
    void calc_costs(Node *node)
    {
        
        if( RE_rayobject_isAligned(node->child) )
        {
            int nchilds = 0;
            for(Node *child = node->child; child && RE_rayobject_isAligned(child); child = child->sibling)
            {
                calc_costs(child);
                nchilds++;
            }

            for(int i=0; i<MAX_CUT_SIZE; i++)
                node->cut_cost[i] = INFINITY;

            //We are not allowed to look on nodes with with so many childs
            if(nchilds > MAX_CUT_SIZE)
            {
                float cost = 0;

                float parent_area = bb_area(node->bb, node->bb+3);
                for(Node *child = node->child; child && RE_rayobject_isAligned(child); child = child->sibling)
                {
                    cost += ((parent_area != 0.0f)? ( bb_area(child->bb, child->bb+3) / parent_area ): 1.0f) * child->get_cost(1);
                }
                
                cost += testcost(nchilds);
                node->cut_cost[0] = cost;
                node->best_cutsize = nchilds;
            }
            else
            {
                calc_best calc(node);
        
                //calc expected cost if we optimaly pack this node
                for(int cutsize=nchilds; cutsize<=MAX_CUT_SIZE; cutsize++)
                {
                    float m = node->get_cost(cutsize) + testcost(cutsize);
                    if(m < node->cut_cost[0])
                    {
                        node->cut_cost[0] = m;
                        node->best_cutsize = cutsize;
                    }
                }
            }
            assert(node->cut_cost[0] != INFINITY);
        }
        else
        {
            node->cut_cost[0] = 1.0f;
            for(int i=1; i<MAX_CUT_SIZE; i++)
                node->cut_cost[i] = INFINITY;
        }
    }

    Node *transform(Node *node)
    {
        if(RE_rayobject_isAligned(node->child))
        {
            static int num = 0;
            bool first = false;
            if(num == 0) { num++; first = true; }
            
            calc_costs(node);
            if((G.f & G_DEBUG) && first) printf("expected cost = %f (%d)\n", node->cut_cost[0], node->best_cutsize );
            node->optimize();
        }
        return node;        
    }   
};