overlap method
This function can be overridden if the original chains are needed
@param start1 the index of the start of the overlapping segment from mc1 @param start2 the index of the start of the overlapping segment from mc2
Implementation
void overlap(MonotoneChainI mc1, int start1, MonotoneChainI mc2, int start2) {
SegmentString ss1 = mc1.getContext() as SegmentString;
SegmentString ss2 = mc2.getContext() as SegmentString;
si.processIntersections(ss1, start1, ss2, start2);
}