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Halfedge linked list #33

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Halfedge linked list #33

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7324fa7
Adding linked list object
fjwong Jan 19, 2017
30fec96
Move linked list to cell prototype
fjwong Jan 19, 2017
abbf69a
Modifying methods to use halfedge linked list
fjwong Jan 19, 2017
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207 changes: 160 additions & 47 deletions rhill-voronoi-core.js
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Original file line number Diff line number Diff line change
Expand Up @@ -430,13 +430,13 @@ Voronoi.prototype.Diagram = function(site) {

Voronoi.prototype.Cell = function(site) {
this.site = site;
this.halfedges = [];
this.halfedges = new this.HalfedgeList();
this.closeMe = false;
};

Voronoi.prototype.Cell.prototype.init = function(site) {
this.site = site;
this.halfedges = [];
this.halfedges.reset();
this.closeMe = false;
return this;
};
Expand All @@ -451,40 +451,44 @@ Voronoi.prototype.createCell = function(site) {

Voronoi.prototype.Cell.prototype.prepareHalfedges = function() {
var halfedges = this.halfedges,
iHalfedge = halfedges.length,
halfedge = halfedges.first,
edge;
// get rid of unused halfedges
// rhill 2011-05-27: Keep it simple, no point here in trying
// to be fancy: dangling edges are a typically a minority.
while (iHalfedge--) {
edge = halfedges[iHalfedge].edge;
while(halfedge) {
edge = halfedge.edge;
if (!edge.vb || !edge.va) {
halfedges.splice(iHalfedge,1);
halfedges.remove(halfedge);
}
halfedge = halfedge.next;
}

// rhill 2011-05-26: I tried to use a binary search at insertion
// time to keep the array sorted on-the-fly (in Cell.addHalfedge()).
// There was no real benefits in doing so, performance on
// Firefox 3.6 was improved marginally, while performance on
// Opera 11 was penalized marginally.
halfedges.sort(function(a,b){return b.angle-a.angle;});

halfedges.sort();

return halfedges.length;
};

// Return a list of the neighbor Ids
Voronoi.prototype.Cell.prototype.getNeighborIds = function() {
var neighbors = [],
iHalfedge = this.halfedges.length,
halfedge = this.halfedges.last,
edge;
while (iHalfedge--){
edge = this.halfedges[iHalfedge].edge;
while (halfedge){
edge = halfedge.edge;
if (edge.lSite !== null && edge.lSite.voronoiId != this.site.voronoiId) {
neighbors.push(edge.lSite.voronoiId);
}
else if (edge.rSite !== null && edge.rSite.voronoiId != this.site.voronoiId){
neighbors.push(edge.rSite.voronoiId);
}
halfedge = halfedge.prev;
}
return neighbors;
};
Expand All @@ -493,14 +497,14 @@ Voronoi.prototype.Cell.prototype.getNeighborIds = function() {
//
Voronoi.prototype.Cell.prototype.getBbox = function() {
var halfedges = this.halfedges,
iHalfedge = halfedges.length,
halfedge = halfedges.last,
xmin = Infinity,
ymin = Infinity,
xmax = -Infinity,
ymax = -Infinity,
v, vx, vy;
while (iHalfedge--) {
v = halfedges[iHalfedge].getStartpoint();
while (halfedge) {
v = halfedge.getStartpoint();
vx = v.x;
vy = v.y;
if (vx < xmin) {xmin = vx;}
Expand All @@ -509,6 +513,7 @@ Voronoi.prototype.Cell.prototype.getBbox = function() {
if (vy > ymax) {ymax = vy;}
// we dont need to take into account end point,
// since each end point matches a start point
halfedge = halfedge.prev;
}
return {
x: xmin,
Expand Down Expand Up @@ -537,11 +542,9 @@ Voronoi.prototype.Cell.prototype.pointIntersection = function(x, y) {
// "if greater than 0 it is to the left, if equal to 0 then it lies
// "on the line segment"
var halfedges = this.halfedges,
iHalfedge = halfedges.length,
halfedge,
halfedge = halfedges.last,
p0, p1, r;
while (iHalfedge--) {
halfedge = halfedges[iHalfedge];
while (halfedge) {
p0 = halfedge.getStartpoint();
p1 = halfedge.getEndpoint();
r = (y-p0.y)*(p1.x-p0.x)-(x-p0.x)*(p1.y-p0.y);
Expand All @@ -551,10 +554,123 @@ Voronoi.prototype.Cell.prototype.pointIntersection = function(x, y) {
if (r > 0) {
return -1;
}
halfedge = halfedge.prev;
}
return 1;
};

// ---------------------------------------------------------------------------
// Halfedge Linked List

Voronoi.prototype.Cell.prototype.HalfedgeList = function() {
this.length = 0;
this.first = null;
this.last = null;
};

Voronoi.prototype.Cell.prototype.HalfedgeList.prototype.reset = function() {
this.length = 0;
this.first = null;
this.last = null;
};

Voronoi.prototype.Cell.prototype.HalfedgeList.prototype.push = function(element) {
if(this.last) {
this.last.next = element;
element.prev = this.last;
this.last = element;
}
else {
this.first = this.last = element;
}
++this.length;
};

Voronoi.prototype.Cell.prototype.HalfedgeList.prototype.remove = function(element) {
if(element.prev && element.next) {
element.prev.next = element.next;
element.next.prev = element.prev;
}
else if(element.prev) {
element.prev.next = null;
this.last = element.prev;
}
else if(element.next) {
element.next.prev = null;
this.first = element.next;
}

--this.length;

if(!this.length) {
this.first = null;
this.last = null;
}
};

Voronoi.prototype.Cell.prototype.HalfedgeList.prototype.insertAfter = function(prev,element) {
element.next = prev.next;

if(prev.next) {
prev.next.prev = element;
}
else {
this.last = element;
}

prev.next = element;
element.prev = prev;

++this.length;
};

Voronoi.prototype.Cell.prototype.HalfedgeList.prototype.sort = function() {
// NOTE: This is a simple insertion sort as usually the amount of halfedges per cell
// is not large enough to benefit from quicksort or other O(n log n) sorting methods.

if(this.length < 2) {
return;
}

var current = this.first,
next = current.next;

while(next) {
current = next;
next = next.next;

var prev = current.prev,
x = current.angle;

if(prev.angle < x) {
while(prev && prev.angle < x) {
prev = prev.prev;
}

current.prev.next = current.next;
if(current.next) {
current.next.prev = current.prev;
}
else {
this.last = current.prev;
}

current.prev = prev;

if(prev) {
current.next = prev.next;
prev.next = current;
}
else {
current.next = this.first;
this.first = current;
}

current.next.prev = current;
}
}
};

// ---------------------------------------------------------------------------
// Edge methods
//
Expand All @@ -573,6 +689,11 @@ Voronoi.prototype.Edge = function(lSite, rSite) {
Voronoi.prototype.Halfedge = function(edge, lSite, rSite) {
this.site = lSite;
this.edge = edge;

// Linked list properties
this.prev = null;
this.next = null;

// 'angle' is a value to be used for properly sorting the
// halfsegments counterclockwise. By convention, we will
// use the angle of the line defined by the 'site to the left'
Expand Down Expand Up @@ -1352,7 +1473,7 @@ Voronoi.prototype.clipEdge = function(edge, bbox) {
if (r>t1) {return false;}
if (r>t0) {t0=r;}
}
// bottom
// bottom
q = bbox.yb-ay;
if (dy===0 && q<0) {return false;}
r = q/dy;
Expand Down Expand Up @@ -1429,8 +1550,8 @@ Voronoi.prototype.closeCells = function(bbox) {
cells = this.cells,
iCell = cells.length,
cell,
iLeft,
halfedges, nHalfedges,
halfedges,
halfedge,
edge,
va, vb, vz,
lastBorderSegment,
Expand All @@ -1450,15 +1571,14 @@ Voronoi.prototype.closeCells = function(bbox) {
// an 'unclosed' point will be the end point of a halfedge which
// does not match the start point of the following halfedge
halfedges = cell.halfedges;
nHalfedges = halfedges.length;
halfedge = halfedges.first;
// special case: only one site, in which case, the viewport is the cell
// ...

// all other cases
iLeft = 0;
while (iLeft < nHalfedges) {
va = halfedges[iLeft].getEndpoint();
vz = halfedges[(iLeft+1) % nHalfedges].getStartpoint();
while (halfedge) {
va = halfedge.getEndpoint();
vz = (halfedge.next || halfedges.first).getStartpoint();
// if end point is not equal to start point, we need to add the missing
// halfedge(s) up to vz
if (abs_fn(va.x-vz.x)>=1e-9 || abs_fn(va.y-vz.y)>=1e-9) {
Expand All @@ -1475,9 +1595,8 @@ Voronoi.prototype.closeCells = function(bbox) {
lastBorderSegment = this.equalWithEpsilon(vz.x,xl);
vb = this.createVertex(xl, lastBorderSegment ? vz.y : yb);
edge = this.createBorderEdge(cell.site, va, vb);
iLeft++;
halfedges.splice(iLeft, 0, this.createHalfedge(edge, cell.site, null));
nHalfedges++;
halfedges.insertAfter(halfedge, this.createHalfedge(edge, cell.site, null));
halfedge = halfedge.next;
if ( lastBorderSegment ) { break; }
va = vb;
// fall through
Expand All @@ -1487,9 +1606,8 @@ Voronoi.prototype.closeCells = function(bbox) {
lastBorderSegment = this.equalWithEpsilon(vz.y,yb);
vb = this.createVertex(lastBorderSegment ? vz.x : xr, yb);
edge = this.createBorderEdge(cell.site, va, vb);
iLeft++;
halfedges.splice(iLeft, 0, this.createHalfedge(edge, cell.site, null));
nHalfedges++;
halfedges.insertAfter(halfedge, this.createHalfedge(edge, cell.site, null));
halfedge = halfedge.next;
if ( lastBorderSegment ) { break; }
va = vb;
// fall through
Expand All @@ -1499,9 +1617,8 @@ Voronoi.prototype.closeCells = function(bbox) {
lastBorderSegment = this.equalWithEpsilon(vz.x,xr);
vb = this.createVertex(xr, lastBorderSegment ? vz.y : yt);
edge = this.createBorderEdge(cell.site, va, vb);
iLeft++;
halfedges.splice(iLeft, 0, this.createHalfedge(edge, cell.site, null));
nHalfedges++;
halfedges.insertAfter(halfedge, this.createHalfedge(edge, cell.site, null));
halfedge = halfedge.next;
if ( lastBorderSegment ) { break; }
va = vb;
// fall through
Expand All @@ -1511,9 +1628,8 @@ Voronoi.prototype.closeCells = function(bbox) {
lastBorderSegment = this.equalWithEpsilon(vz.y,yt);
vb = this.createVertex(lastBorderSegment ? vz.x : xl, yt);
edge = this.createBorderEdge(cell.site, va, vb);
iLeft++;
halfedges.splice(iLeft, 0, this.createHalfedge(edge, cell.site, null));
nHalfedges++;
halfedges.insertAfter(halfedge, this.createHalfedge(edge, cell.site, null));
halfedge = halfedge.next;
if ( lastBorderSegment ) { break; }
va = vb;
// fall through
Expand All @@ -1522,9 +1638,8 @@ Voronoi.prototype.closeCells = function(bbox) {
lastBorderSegment = this.equalWithEpsilon(vz.x,xl);
vb = this.createVertex(xl, lastBorderSegment ? vz.y : yb);
edge = this.createBorderEdge(cell.site, va, vb);
iLeft++;
halfedges.splice(iLeft, 0, this.createHalfedge(edge, cell.site, null));
nHalfedges++;
halfedges.insertAfter(halfedge, this.createHalfedge(edge, cell.site, null));
halfedge = halfedge.next;
if ( lastBorderSegment ) { break; }
va = vb;
// fall through
Expand All @@ -1533,9 +1648,8 @@ Voronoi.prototype.closeCells = function(bbox) {
lastBorderSegment = this.equalWithEpsilon(vz.y,yb);
vb = this.createVertex(lastBorderSegment ? vz.x : xr, yb);
edge = this.createBorderEdge(cell.site, va, vb);
iLeft++;
halfedges.splice(iLeft, 0, this.createHalfedge(edge, cell.site, null));
nHalfedges++;
halfedges.insertAfter(halfedge, this.createHalfedge(edge, cell.site, null));
halfedge = halfedge.next;
if ( lastBorderSegment ) { break; }
va = vb;
// fall through
Expand All @@ -1544,17 +1658,16 @@ Voronoi.prototype.closeCells = function(bbox) {
lastBorderSegment = this.equalWithEpsilon(vz.x,xr);
vb = this.createVertex(xr, lastBorderSegment ? vz.y : yt);
edge = this.createBorderEdge(cell.site, va, vb);
iLeft++;
halfedges.splice(iLeft, 0, this.createHalfedge(edge, cell.site, null));
nHalfedges++;
halfedges.insertAfter(halfedge, this.createHalfedge(edge, cell.site, null));
halfedge = halfedge.next;
if ( lastBorderSegment ) { break; }
// fall through

default:
throw "Voronoi.closeCells() > this makes no sense!";
}
}
iLeft++;
halfedge = halfedge.next;
}
cell.closeMe = false;
}
Expand Down