function selfIntersections(poly, filterFn) {
var seen = {};
var l = poly.length;
var isects = [];
for (var o=0; o<l; o++) {
var s0 = poly[o];
var e0 = poly[(o+1) % l];
arrayOrObject(s0, oc);
arrayOrObject(e0, on);
for (var p=0; p<l; p++) {
if (o === p) { continue; }
var s1 = poly[p]
var e1 = poly[(p+1) % l];
arrayOrObject(s1, pc);
arrayOrObject(e1, pn);
if (cmp(pc, oc) || cmp(pc, on) || cmp(pn, oc) || cmp(pn, on)) {
continue;
}
var r = isect(oc, on, pc, pn);
// since these are homogeneous vectors, if the last component `w` is 0
// then we've done something wrong
var wraw = r[2];
if (wraw.length === 1 && !wraw[0]) {
continue;
}
var w = float(r[2]);
r[0] = float(r[0]) / w;
r[1] = float(r[1]) / w;
r.pop();
if (cmp(r, oc) || cmp(r, on) || cmp(r, pc) || cmp(r, pn)) {
continue;
}
var key = r+'';
var unique = !seen[key];
if (unique) {
seen[key] = true;
}
var collect = unique;
if (filterFn) {
collect = filterFn(r, o, s0, e0, p, s1, e1, unique);
}
if (collect) {
isects.push(r);
}
}
}
return isects;
}
function isect(a, b, fn) {
var ret = [];
var al = a.cells.length;
var bl = b.cells.length;
for (var ai = 0; ai<al; ai++) {
var astart = a.positions[a.cells[ai][0]]
var aend = a.positions[a.cells[ai][1]]
for (var bi = 0; bi<bl; bi++) {
var bstart = b.positions[b.cells[bi][0]];
var bend = b.positions[b.cells[bi][1]];
if (doesIsect(astart, aend, bstart, bend)) {
var r = segseg(
astart,
aend,
bstart,
bend
);
if (fn) {
var res = fn(r, ret.length)
if (res) {
ret.push(res);
} else {
ret.push(r);
}
} else {
ret.push(r);
}
}
}
}
return ret;
}