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Avoid array usage to store disappearing transitions on beachsection removal #32

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Avoid array usage to store disappearing transitions on beachsection removal #32

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37 changes: 16 additions & 21 deletions rhill-voronoi-core.js
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Original file line number Diff line number Diff line change
Expand Up @@ -800,7 +800,6 @@ Voronoi.prototype.removeBeachsection = function(beachsection) {
vertex = this.createVertex(x, y),
previous = beachsection.rbPrevious,
next = beachsection.rbNext,
disappearingTransitions = [beachsection],
abs_fn = Math.abs;

// remove collapsed beachsection from beachline
Expand All @@ -816,51 +815,47 @@ Voronoi.prototype.removeBeachsection = function(beachsection) {
// on their left/right side.

// look left
var lArc = previous;
while (lArc.circleEvent && abs_fn(x-lArc.circleEvent.x)<1e-9 && abs_fn(y-lArc.circleEvent.ycenter)<1e-9) {
var lArc = previous,
circleEvent = lArc.circleEvent;

this.setEdgeStartpoint(beachsection.edge, lArc.site, beachsection.site, vertex);

while (circleEvent && abs_fn(x-circleEvent.x)<1e-9 && abs_fn(y-circleEvent.ycenter)<1e-9) {
previous = lArc.rbPrevious;
disappearingTransitions.unshift(lArc);
this.detachBeachsection(lArc); // mark for reuse
this.setEdgeStartpoint(lArc.edge, previous.site, lArc.site, vertex);
lArc = previous;
circleEvent = lArc.circleEvent;
}
// even though it is not disappearing, I will also add the beach section
// immediately to the left of the left-most collapsed beach section, for
// convenience, since we need to refer to it later as this beach section
// is the 'left' site of an edge for which a start point is set.
disappearingTransitions.unshift(lArc);
this.detachCircleEvent(lArc);

// look right
var rArc = next;
while (rArc.circleEvent && abs_fn(x-rArc.circleEvent.x)<1e-9 && abs_fn(y-rArc.circleEvent.ycenter)<1e-9) {
circleEvent = rArc.circleEvent;

this.setEdgeStartpoint(rArc.edge, beachsection.site, rArc.site, vertex);

while (circleEvent && abs_fn(x-circleEvent.x)<1e-9 && abs_fn(y-circleEvent.ycenter)<1e-9) {
next = rArc.rbNext;
disappearingTransitions.push(rArc);
this.detachBeachsection(rArc); // mark for reuse
this.setEdgeStartpoint(next.edge, rArc.site, next.site, vertex);
rArc = next;
circleEvent = rArc.circleEvent;
}
// we also have to add the beach section immediately to the right of the
// right-most collapsed beach section, since there is also a disappearing
// transition representing an edge's start point on its left.
disappearingTransitions.push(rArc);
this.detachCircleEvent(rArc);

// walk through all the disappearing transitions between beach sections and
// set the start point of their (implied) edge.
var nArcs = disappearingTransitions.length,
iArc;
for (iArc=1; iArc<nArcs; iArc++) {
rArc = disappearingTransitions[iArc];
lArc = disappearingTransitions[iArc-1];
this.setEdgeStartpoint(rArc.edge, lArc.site, rArc.site, vertex);
}

// create a new edge as we have now a new transition between
// two beach sections which were previously not adjacent.
// since this edge appears as a new vertex is defined, the vertex
// actually define an end point of the edge (relative to the site
// on the left)
lArc = disappearingTransitions[0];
rArc = disappearingTransitions[nArcs-1];
rArc.edge = this.createEdge(lArc.site, rArc.site, undefined, vertex);

// create circle events if any for beach sections left in the beachline
Expand Down Expand Up @@ -1352,7 +1347,7 @@ 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