/* returns true if p is to right of halfedge e */
private bool right_of(Halfedge el, DoubleVector2 p)
{
Edge e;
Site topsite;
bool right_of_site;
bool above, fast;
double dxp, dyp, dxs, t1, t2, t3, yl;
e = el.ELedge;
topsite = e.reg[1];
if ( p.X > topsite.Coord.X )
right_of_site = true;
else
right_of_site = false;
if ( right_of_site && el.ELpm == LE )
return true;
if (!right_of_site && el.ELpm == RE )
return false;
if ( e.a == 1.0 )
{
dxp = p.X - topsite.Coord.X;
dyp = p.Y - topsite.Coord.Y;
fast = false;
if ( (!right_of_site & (e.b < 0.0)) | (right_of_site & (e.b >= 0.0)) )
{
above = dyp >= e.b * dxp;
fast = above;
}
else
{
above = p.X + p.Y * e.b > e.c;
if ( e.b < 0.0 )
above = !above;
if ( !above )
fast = true;
}
if ( !fast )
{
dxs = topsite.Coord.X - ( e.reg[0] ).Coord.X;
above = e.b * (dxp * dxp - dyp * dyp)
< dxs * dyp * (1.0 + 2.0 * dxp / dxs + e.b * e.b);
if ( e.b < 0 )
above = !above;
}
}
else // e.b == 1.0
{
yl = e.c - e.a * p.X;
t1 = p.Y - yl;
t2 = p.X - topsite.Coord.X;
t3 = yl - topsite.Coord.Y;
above = t1 * t1 > t2 * t2 + t3 * t3;
}
return ( el.ELpm == LE ? above : !above );
}
public int Compare ( Site p1, Site p2 )
{
DoubleVector2 s1 = p1.Coord;
DoubleVector2 s2 = p2.Coord;
if ( s1.Y < s2.Y ) return -1;
if ( s1.Y > s2.Y ) return 1;
if ( s1.X < s2.X ) return -1;
if ( s1.X > s2.X ) return 1;
return 0;
}
private DoubleVector2 PQ_min ()
{
DoubleVector2 answer = new DoubleVector2 ();
while ( PQhash[PQmin].PQnext == null )
{
PQmin++;
}
answer.X = PQhash[PQmin].PQnext.vertex.Coord.X;
answer.Y = PQhash[PQmin].PQnext.ystar;
return answer;
}
public int Compare(Site p1, Site p2)
{
DoubleVector2 s1 = p1.Coord;
DoubleVector2 s2 = p2.Coord;
if (s1.Y < s2.Y)
{
return(-1);
}
if (s1.Y > s2.Y)
{
return(1);
}
if (s1.X < s2.X)
{
return(-1);
}
if (s1.X > s2.X)
{
return(1);
}
return(0);
}
public Site()
{
Coord = new DoubleVector2();
}
/*
* implicit parameters: nsites, sqrt_nsites, xmin, xmax, ymin, ymax, deltax,
* deltay (can all be estimates). Performance suffers if they are wrong;
* better to make nsites, deltax, and deltay too big than too small. (?)
*/
private bool voronoi_bd()
{
Site newsite, bot, top, temp, p;
Site v;
DoubleVector2 newintstar = null;
int pm;
Halfedge lbnd, rbnd, llbnd, rrbnd, bisector;
Edge e;
PQinitialize();
ELinitialize();
bottomsite = nextone();
newsite = nextone();
while (true)
{
if (!PQempty())
{
newintstar = PQ_min();
}
// if the lowest site has a smaller y value than the lowest vector
// intersection,
// process the site otherwise process the vector intersection
if (newsite != null && (PQempty()
|| newsite.Coord.Y < newintstar.Y
|| (newsite.Coord.Y == newintstar.Y
&& newsite.Coord.X < newintstar.X)))
{
/* new site is smallest -this is a site event */
// get the first HalfEdge to the LEFT of the new site
lbnd = ELleftbnd((newsite.Coord));
// get the first HalfEdge to the RIGHT of the new site
rbnd = ELright(lbnd);
// if this halfedge has no edge,bot =bottom site (whatever that
// is)
bot = rightreg(lbnd);
// create a new edge that bisects
e = bisect(bot, newsite);
// create a new HalfEdge, setting its ELpm field to 0
bisector = HEcreate(e, LE);
// insert this new bisector edge between the left and right
// vectors in a linked list
ELinsert(lbnd, bisector);
// if the new bisector intersects with the left edge,
// remove the left edge's vertex, and put in the new one
if ((p = intersect(lbnd, bisector)) != null)
{
PQdelete(lbnd);
PQinsert(lbnd, p, dist(p, newsite));
}
lbnd = bisector;
// create a new HalfEdge, setting its ELpm field to 1
bisector = HEcreate(e, RE);
// insert the new HE to the right of the original bisector
// earlier in the IF stmt
ELinsert(lbnd, bisector);
// if this new bisector intersects with the new HalfEdge
if ((p = intersect(bisector, rbnd)) != null)
{
// push the HE into the ordered linked list of vertices
PQinsert(bisector, p, dist(p, newsite));
}
newsite = nextone();
} else if (!PQempty())
/* intersection is smallest - this is a vector event */
{
// pop the HalfEdge with the lowest vector off the ordered list
// of vectors
lbnd = PQextractmin();
// get the HalfEdge to the left of the above HE
llbnd = ELleft(lbnd);
// get the HalfEdge to the right of the above HE
rbnd = ELright(lbnd);
// get the HalfEdge to the right of the HE to the right of the
// lowest HE
rrbnd = ELright(rbnd);
// get the Site to the left of the left HE which it bisects
bot = leftreg(lbnd);
// get the Site to the right of the right HE which it bisects
top = rightreg(rbnd);
v = lbnd.vertex; // get the vertex that caused this event
makevertex(v); // set the vertex number - couldn't do this
// earlier since we didn't know when it would be processed
endpoint(lbnd.ELedge, lbnd.ELpm, v);
// set the endpoint of
// the left HalfEdge to be this vector
endpoint(rbnd.ELedge, rbnd.ELpm, v);
// set the endpoint of the right HalfEdge to
// be this vector
ELdelete(lbnd); // mark the lowest HE for
// deletion - can't delete yet because there might be pointers
// to it in Hash Map
PQdelete(rbnd);
// remove all vertex events to do with the right HE
ELdelete(rbnd); // mark the right HE for
// deletion - can't delete yet because there might be pointers
// to it in Hash Map
pm = LE; // set the pm variable to zero
if (bot.Coord.Y > top.Coord.Y)
// if the site to the left of the event is higher than the
// Site
{ // to the right of it, then swap them and set the 'pm'
// variable to 1
temp = bot;
bot = top;
top = temp;
pm = RE;
}
e = bisect(bot, top); // create an Edge (or line)
// that is between the two Sites. This creates the formula of
// the line, and assigns a line number to it
bisector = HEcreate(e, pm); // create a HE from the Edge 'e',
// and make it point to that edge
// with its ELedge field
ELinsert(llbnd, bisector); // insert the new bisector to the
// right of the left HE
endpoint(e, RE - pm, v); // set one endpoint to the new edge
// to be the vector point 'v'.
// If the site to the left of this bisector is higher than the
// right Site, then this endpoint
// is put in position 0; otherwise in pos 1
// if left HE and the new bisector intersect, then delete
// the left HE, and reinsert it
if ((p = intersect(llbnd, bisector)) != null)
{
PQdelete(llbnd);
PQinsert(llbnd, p, dist(p, bot));
}
// if right HE and the new bisector intersect, then
// reinsert it
if ((p = intersect(bisector, rrbnd)) != null)
{
PQinsert(bisector, p, dist(p, bot));
}
} else
{
break;
}
}
for (lbnd = ELright(ELleftend); lbnd != ELrightend; lbnd = ELright(lbnd))
{
e = lbnd.ELedge;
clip_line(e);
}
return true;
}
private Halfedge ELleftbnd( DoubleVector2 p )
{
int bucket;
Halfedge he;
/* Use hash table to get close to desired halfedge */
// use the hash function to find the place in the hash map that this
// HalfEdge should be
bucket = (int) ((p.X - xmin) / deltax * ELhashsize);
// make sure that the bucket position is within the range of the hash
// array
if ( bucket < 0 ) bucket = 0;
if ( bucket >= ELhashsize ) bucket = ELhashsize - 1;
he = ELgethash ( bucket );
// if the HE isn't found, search backwards and forwards in the hash map
// for the first non-null entry
if ( he == null )
{
for ( int i = 1; i < ELhashsize; i++ )
{
if ( (he = ELgethash ( bucket - i ) ) != null )
break;
if ( (he = ELgethash ( bucket + i ) ) != null )
break;
}
}
/* Now search linear list of halfedges for the correct one */
if ( he == ELleftend || ( he != ELrightend && right_of (he, p) ) )
{
// keep going right on the list until either the end is reached, or
// you find the 1st edge which the point isn't to the right of
do
{
he = he.ELright;
}
while ( he != ELrightend && right_of(he, p) );
he = he.ELleft;
}
else
// if the point is to the left of the HalfEdge, then search left for
// the HE just to the left of the point
{
do
{
he = he.ELleft;
}
while ( he != ELleftend && !right_of(he, p) );
}
/* Update hash table and reference counts */
if ( bucket > 0 && bucket < ELhashsize - 1)
{
ELhash[bucket] = he;
}
return he;
}
