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kdtree.cpp
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kdtree.cpp
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/*
Copyright 2008 Utah State University
This file is part of OIP.
OIP 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 3 of the License, or
(at your option) any later version.
OIP 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 OIP. If not, see <http://www.gnu.org/licenses/>.
*/
#include "kdtree.h"
//see if point and other->point are within distance of each other
bool kdnode::closeto(float x, float y, float distance)
{
if (point &&
(x - point->getX()) *
(x - point->getX()) +
(y - point->getY()) *
(y - point->getY()) < distance * distance )
return true;
return false;
}
/*
* This function will divide the given list of nodes into two sets, based on which dimension we are dividing
* precondition:
* r is a node with no valid information
* plist is a list of particles that need to be placed into r
* postcondition:
* r->point contains a particle from plist
* r->left contains a new node if there are particles less than r->point. likewies for r->right
*/
void kdtree::maketree(kdnode* r, vector<particle*> & plist, bool xplane)
{
//select three random nodes
particle* r1 = plist[rand() % plist.size()];
particle* r2 = plist[rand() % plist.size()];
particle* r3 = plist[rand() % plist.size()];
particle* mid;
vector<particle*> leftl;
vector<particle*> rightl;
typedef vector<particle*> myv; //working around _yet_ another mvc++ bug
if (xplane) //do we sort between the x coordinates?
{
if (r1->getX() < r2->getX() && r2->getX() < r3->getX())
mid = r2;
else if (r2->getX() < r1->getX() && r1->getX() < r3->getX())
mid = r1;
else
mid = r3;
//set the particle to the node, and divide the remainder
myv::iterator i = plist.begin();
//vector<particle*>::iterator i = plist.begin();
for(;i!= plist.end(); i++)
{
if ((*i)->getX() < mid->getX())
leftl.push_back(*i);
else if ((*i)->getX() > mid->getX())
rightl.push_back(*i);
}
}
else
{
if (r1->getY() < r2->getY() && r2->getY() < r3->getY())
mid = r2;
else if (r2->getY() < r1->getY() && r1->getY() < r3->getY())
mid = r1;
else
mid = r3;
//set the particle to the node, and divide the remainder
myv::iterator i = plist.begin();
for(;i!= plist.end(); i++)
{
if ((*i)->getY() < mid->getY())
leftl.push_back(*i);
else if ((*i)->getY() > mid->getY())
rightl.push_back(*i);
}
}
//allocate two nodes, if necessary
if (leftl.size())
{
r->left = new kdnode();
maketree(r->left, leftl, !xplane);
}
if (rightl.size())
{
r->right = new kdnode();
maketree(r->right, rightl, !xplane);
}
//save the particle at the midpoint
r->point = mid;
}
/*
* recursive function that gathers particles near a particular point.
* it walks through the tree, eliminating branches it doesnt need to search
*/
void kdtree::collect(kdnode* r, float distance, float x, float y, vector<particle*>& pnear, float x0, float y0, float x1, float y1, bool xplane)
{
//is this nodes point within the distance?
if (r->closeto(x, y, distance))
pnear.push_back(r->point);
if (xplane)
{
//what children should we consider?
if (r->left && x > x0-distance && x < r->point->getX()+distance &&
y > y0-distance && y < y1+distance)
collect(r->left, distance, x, y, pnear, x0, y0, r->point->getX(), y1, false);
if (r->right && x > r->point->getX() -distance && x < x1 + distance &&
y > y0-distance && y < y1+distance)
collect(r->right, distance, x, y, pnear, r->point->getX(), y0, x1, y1, false);
}
else
{
//what children should we consider?
if (r->left && x > x0-distance && x < y1+distance &&
y > y0-distance && y < r->point->getY()+distance)
collect(r->left, distance, x, y, pnear, x0, y0, x1, r->point->getY(), true);
if (r->right && x > x0-distance && x < x1 + distance &&
y > r->point->getY()-distance && y < y1+distance)
collect(r->right, distance, x, y, pnear, x0, r->point->getY(), x1, y1, true);
}
}
kdtree::kdtree(vector<particle*> & plist)
{
if (plist.size())
{
root = new kdnode();
maketree(root, plist, true);
}
else
root = NULL;
}
void kdtree::erase(kdnode* r)
{
if (r->left)
erase(r->left);
if (r->right)
erase(r->right);
r->left = NULL;
r->right = NULL;
delete r;
}
kdtree::~kdtree()
{
if (root)
erase(root);
root = NULL;
}
void kdtree::collect(float distance, float x, float y, vector<particle*>&pnear)
{
if (root)
collect(root, distance, x, y, pnear, 0, 0, 1, 1, true);
}