/**
* Because Delete Events have a link to their corresponding Insert event, it is possible to
* compute exactly the range of events which must be compared to a given Insert event object.
*/
private void prepareEvents() {
Collections.sort(events);
for (int i = 0; i < events.size(); i++) {
SweepLineEvent ev = (SweepLineEvent) events.get(i);
if (ev.isDelete()) {
ev.getInsertEvent().setDeleteEventIndex(i);
}
}
}
private void computeIntersections(SegmentIntersector si) {
nOverlaps = 0;
prepareEvents();
for (int i = 0; i < events.size(); i++) {
SweepLineEvent ev = (SweepLineEvent) events.get(i);
if (ev.isInsert()) {
processOverlaps(i, ev.getDeleteEventIndex(), ev, si);
}
}
}
private void processOverlaps(int start, int end, SweepLineEvent ev0, SegmentIntersector si) {
SweepLineSegment ss0 = (SweepLineSegment) ev0.getObject();
/**
* Since we might need to test for self-intersections, include current insert event object in
* list of event objects to test. Last index can be skipped, because it must be a Delete event.
*/
for (int i = start; i < end; i++) {
SweepLineEvent ev1 = (SweepLineEvent) events.get(i);
if (ev1.isInsert()) {
SweepLineSegment ss1 = (SweepLineSegment) ev1.getObject();
if (ev0.edgeSet == null || (ev0.edgeSet != ev1.edgeSet)) {
ss0.computeIntersections(ss1, si);
nOverlaps++;
}
}
}
}