btGImpactBvh.cpp

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/*
This source file is part of GIMPACT Library.

For the latest info, see http://gimpact.sourceforge.net/

Copyright (c) 2007 Francisco Leon Najera. C.C. 80087371.
email: projectileman@yahoo.com


This software is provided 'as-is', without any express or implied warranty.
In no event will the authors be held liable for any damages arising from the use of this software.
Permission is granted to anyone to use this software for any purpose,
including commercial applications, and to alter it and redistribute it freely,
subject to the following restrictions:

1. The origin of this software must not be misrepresented; you must not claim that you wrote the original software. If you use this software in a product, an acknowledgment in the product documentation would be appreciated but is not required.
2. Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software.
3. This notice may not be removed or altered from any source distribution.
*/
#include "btGImpactBvh.h"
#include "LinearMath/btQuickprof.h"

#ifdef TRI_COLLISION_PROFILING

btClock g_tree_clock;

float g_accum_tree_collision_time = 0;
int g_count_traversing = 0;


void bt_begin_gim02_tree_time()
{
        g_tree_clock.reset();
}

void bt_end_gim02_tree_time()
{
        g_accum_tree_collision_time += g_tree_clock.getTimeMicroseconds();
        g_count_traversing++;
}

float btGImpactBvh::getAverageTreeCollisionTime()
{
        if(g_count_traversing == 0) return 0;

        float avgtime = g_accum_tree_collision_time;
        avgtime /= (float)g_count_traversing;

        g_accum_tree_collision_time = 0;
        g_count_traversing = 0;
        return avgtime;

//      float avgtime = g_count_traversing;
//      g_count_traversing = 0;
//      return avgtime;

}

#endif //TRI_COLLISION_PROFILING


int btBvhTree::_calc_splitting_axis(
        GIM_BVH_DATA_ARRAY & primitive_boxes, int startIndex,  int endIndex)
{

        int i;

        btVector3 means(btScalar(0.),btScalar(0.),btScalar(0.));
        btVector3 variance(btScalar(0.),btScalar(0.),btScalar(0.));
        int numIndices = endIndex-startIndex;

        for (i=startIndex;i<endIndex;i++)
        {
                btVector3 center = btScalar(0.5)*(primitive_boxes[i].m_bound.m_max +
                                         primitive_boxes[i].m_bound.m_min);
                means+=center;
        }
        means *= (btScalar(1.)/(btScalar)numIndices);

        for (i=startIndex;i<endIndex;i++)
        {
                btVector3 center = btScalar(0.5)*(primitive_boxes[i].m_bound.m_max +
                                         primitive_boxes[i].m_bound.m_min);
                btVector3 diff2 = center-means;
                diff2 = diff2 * diff2;
                variance += diff2;
        }
        variance *= (btScalar(1.)/      ((btScalar)numIndices-1)        );

        return variance.maxAxis();
}


int btBvhTree::_sort_and_calc_splitting_index(
        GIM_BVH_DATA_ARRAY & primitive_boxes, int startIndex,
        int endIndex, int splitAxis)
{
        int i;
        int splitIndex =startIndex;
        int numIndices = endIndex - startIndex;

        // average of centers
        btScalar splitValue = 0.0f;

        btVector3 means(btScalar(0.),btScalar(0.),btScalar(0.));
        for (i=startIndex;i<endIndex;i++)
        {
                btVector3 center = btScalar(0.5)*(primitive_boxes[i].m_bound.m_max +
                                         primitive_boxes[i].m_bound.m_min);
                means+=center;
        }
        means *= (btScalar(1.)/(btScalar)numIndices);

        splitValue = means[splitAxis];


        //sort leafNodes so all values larger then splitValue comes first, and smaller values start from 'splitIndex'.
        for (i=startIndex;i<endIndex;i++)
        {
                btVector3 center = btScalar(0.5)*(primitive_boxes[i].m_bound.m_max +
                                         primitive_boxes[i].m_bound.m_min);
                if (center[splitAxis] > splitValue)
                {
                        //swap
                        primitive_boxes.swap(i,splitIndex);
                        //swapLeafNodes(i,splitIndex);
                        splitIndex++;
                }
        }

        //if the splitIndex causes unbalanced trees, fix this by using the center in between startIndex and endIndex
        //otherwise the tree-building might fail due to stack-overflows in certain cases.
        //unbalanced1 is unsafe: it can cause stack overflows
        //bool unbalanced1 = ((splitIndex==startIndex) || (splitIndex == (endIndex-1)));

        //unbalanced2 should work too: always use center (perfect balanced trees)
        //bool unbalanced2 = true;

        //this should be safe too:
        int rangeBalancedIndices = numIndices/3;
        bool unbalanced = ((splitIndex<=(startIndex+rangeBalancedIndices)) || (splitIndex >=(endIndex-1-rangeBalancedIndices)));

        if (unbalanced)
        {
                splitIndex = startIndex+ (numIndices>>1);
        }

        btAssert(!((splitIndex==startIndex) || (splitIndex == (endIndex))));

        return splitIndex;

}


void btBvhTree::_build_sub_tree(GIM_BVH_DATA_ARRAY & primitive_boxes, int startIndex,  int endIndex)
{
        int curIndex = m_num_nodes;
        m_num_nodes++;

        btAssert((endIndex-startIndex)>0);

        if ((endIndex-startIndex)==1)
        {
            //We have a leaf node
            setNodeBound(curIndex,primitive_boxes[startIndex].m_bound);
                m_node_array[curIndex].setDataIndex(primitive_boxes[startIndex].m_data);

                return;
        }
        //calculate Best Splitting Axis and where to split it. Sort the incoming 'leafNodes' array within range 'startIndex/endIndex'.

        //split axis
        int splitIndex = _calc_splitting_axis(primitive_boxes,startIndex,endIndex);

        splitIndex = _sort_and_calc_splitting_index(
                        primitive_boxes,startIndex,endIndex,
                        splitIndex//split axis
                        );


        //calc this node bounding box

        btAABB node_bound;
        node_bound.invalidate();

        for (int i=startIndex;i<endIndex;i++)
        {
                node_bound.merge(primitive_boxes[i].m_bound);
        }

        setNodeBound(curIndex,node_bound);


        //build left branch
        _build_sub_tree(primitive_boxes, startIndex, splitIndex );


        //build right branch
         _build_sub_tree(primitive_boxes, splitIndex ,endIndex);

        m_node_array[curIndex].setEscapeIndex(m_num_nodes - curIndex);


}

void btBvhTree::build_tree(
        GIM_BVH_DATA_ARRAY & primitive_boxes)
{
        // initialize node count to 0
        m_num_nodes = 0;
        // allocate nodes
        m_node_array.resize(primitive_boxes.size()*2);

        _build_sub_tree(primitive_boxes, 0, primitive_boxes.size());
}


void btGImpactBvh::refit()
{
        int nodecount = getNodeCount();
        while(nodecount--)
        {
                if(isLeafNode(nodecount))
                {
                        btAABB leafbox;
                        m_primitive_manager->get_primitive_box(getNodeData(nodecount),leafbox);
                        setNodeBound(nodecount,leafbox);
                }
                else
                {
                        //const GIM_BVH_TREE_NODE * nodepointer = get_node_pointer(nodecount);
                        //get left bound
                        btAABB bound;
                        bound.invalidate();

                        btAABB temp_box;

                        int child_node = getLeftNode(nodecount);
                        if(child_node)
                        {
                                getNodeBound(child_node,temp_box);
                                bound.merge(temp_box);
                        }

                        child_node = getRightNode(nodecount);
                        if(child_node)
                        {
                                getNodeBound(child_node,temp_box);
                                bound.merge(temp_box);
                        }

                        setNodeBound(nodecount,bound);
                }
        }
}

void btGImpactBvh::buildSet()
{
        //obtain primitive boxes
        GIM_BVH_DATA_ARRAY primitive_boxes;
        primitive_boxes.resize(m_primitive_manager->get_primitive_count());

        for (int i = 0;i<primitive_boxes.size() ;i++ )
        {
                 m_primitive_manager->get_primitive_box(i,primitive_boxes[i].m_bound);
                 primitive_boxes[i].m_data = i;
        }

        m_box_tree.build_tree(primitive_boxes);
}

bool btGImpactBvh::boxQuery(const btAABB & box, btAlignedObjectArray<int> & collided_results) const
{
        int curIndex = 0;
        int numNodes = getNodeCount();

        while (curIndex < numNodes)
        {
                btAABB bound;
                getNodeBound(curIndex,bound);

                //catch bugs in tree data

                bool aabbOverlap = bound.has_collision(box);
                bool isleafnode = isLeafNode(curIndex);

                if (isleafnode && aabbOverlap)
                {
                        collided_results.push_back(getNodeData(curIndex));
                }

                if (aabbOverlap || isleafnode)
                {
                        //next subnode
                        curIndex++;
                }
                else
                {
                        //skip node
                        curIndex+= getEscapeNodeIndex(curIndex);
                }
        }
        if(collided_results.size()>0) return true;
        return false;
}



bool btGImpactBvh::rayQuery(
        const btVector3 & ray_dir,const btVector3 & ray_origin ,
        btAlignedObjectArray<int> & collided_results) const
{
        int curIndex = 0;
        int numNodes = getNodeCount();

        while (curIndex < numNodes)
        {
                btAABB bound;
                getNodeBound(curIndex,bound);

                //catch bugs in tree data

                bool aabbOverlap = bound.collide_ray(ray_origin,ray_dir);
                bool isleafnode = isLeafNode(curIndex);

                if (isleafnode && aabbOverlap)
                {
                        collided_results.push_back(getNodeData( curIndex));
                }

                if (aabbOverlap || isleafnode)
                {
                        //next subnode
                        curIndex++;
                }
                else
                {
                        //skip node
                        curIndex+= getEscapeNodeIndex(curIndex);
                }
        }
        if(collided_results.size()>0) return true;
        return false;
}


SIMD_FORCE_INLINE bool _node_collision(
        btGImpactBvh * boxset0, btGImpactBvh * boxset1,
        const BT_BOX_BOX_TRANSFORM_CACHE & trans_cache_1to0,
        int node0 ,int node1, bool complete_primitive_tests)
{
        btAABB box0;
        boxset0->getNodeBound(node0,box0);
        btAABB box1;
        boxset1->getNodeBound(node1,box1);

        return box0.overlapping_trans_cache(box1,trans_cache_1to0,complete_primitive_tests );
//      box1.appy_transform_trans_cache(trans_cache_1to0);
//      return box0.has_collision(box1);

}


//stackless recursive collision routine
static void _find_collision_pairs_recursive(
        btGImpactBvh * boxset0, btGImpactBvh * boxset1,
        btPairSet * collision_pairs,
        const BT_BOX_BOX_TRANSFORM_CACHE & trans_cache_1to0,
        int node0, int node1, bool complete_primitive_tests)
{



        if( _node_collision(
                boxset0,boxset1,trans_cache_1to0,
                node0,node1,complete_primitive_tests) ==false) return;//avoid colliding internal nodes

        if(boxset0->isLeafNode(node0))
        {
                if(boxset1->isLeafNode(node1))
                {
                        // collision result
                        collision_pairs->push_pair(
                                boxset0->getNodeData(node0),boxset1->getNodeData(node1));
                        return;
                }
                else
                {

                        //collide left recursive

                        _find_collision_pairs_recursive(
                                                                boxset0,boxset1,
                                                                collision_pairs,trans_cache_1to0,
                                                                node0,boxset1->getLeftNode(node1),false);

                        //collide right recursive
                        _find_collision_pairs_recursive(
                                                                boxset0,boxset1,
                                                                collision_pairs,trans_cache_1to0,
                                                                node0,boxset1->getRightNode(node1),false);


                }
        }
        else
        {
                if(boxset1->isLeafNode(node1))
                {

                        //collide left recursive
                        _find_collision_pairs_recursive(
                                                                boxset0,boxset1,
                                                                collision_pairs,trans_cache_1to0,
                                                                boxset0->getLeftNode(node0),node1,false);


                        //collide right recursive

                        _find_collision_pairs_recursive(
                                                                boxset0,boxset1,
                                                                collision_pairs,trans_cache_1to0,
                                                                boxset0->getRightNode(node0),node1,false);


                }
                else
                {
                        //collide left0 left1



                        _find_collision_pairs_recursive(
                                boxset0,boxset1,
                                collision_pairs,trans_cache_1to0,
                                boxset0->getLeftNode(node0),boxset1->getLeftNode(node1),false);

                        //collide left0 right1

                        _find_collision_pairs_recursive(
                                boxset0,boxset1,
                                collision_pairs,trans_cache_1to0,
                                boxset0->getLeftNode(node0),boxset1->getRightNode(node1),false);


                        //collide right0 left1

                        _find_collision_pairs_recursive(
                                boxset0,boxset1,
                                collision_pairs,trans_cache_1to0,
                                boxset0->getRightNode(node0),boxset1->getLeftNode(node1),false);

                        //collide right0 right1

                        _find_collision_pairs_recursive(
                                boxset0,boxset1,
                                collision_pairs,trans_cache_1to0,
                                boxset0->getRightNode(node0),boxset1->getRightNode(node1),false);

                }// else if node1 is not a leaf
        }// else if node0 is not a leaf
}


void btGImpactBvh::find_collision(btGImpactBvh * boxset0, const btTransform & trans0,
                btGImpactBvh * boxset1, const btTransform & trans1,
                btPairSet & collision_pairs)
{

        if(boxset0->getNodeCount()==0 || boxset1->getNodeCount()==0 ) return;

        BT_BOX_BOX_TRANSFORM_CACHE trans_cache_1to0;

        trans_cache_1to0.calc_from_homogenic(trans0,trans1);

#ifdef TRI_COLLISION_PROFILING
        bt_begin_gim02_tree_time();
#endif //TRI_COLLISION_PROFILING

        _find_collision_pairs_recursive(
                boxset0,boxset1,
                &collision_pairs,trans_cache_1to0,0,0,true);
#ifdef TRI_COLLISION_PROFILING
        bt_end_gim02_tree_time();
#endif //TRI_COLLISION_PROFILING

}