private void ComputeOverlaps(int start0, int end0, MonotoneChain mc,
int start1, int end1, MonotoneChainOverlapAction mco)
{
Coordinate p00 = pts[start0];
Coordinate p01 = pts[end0];
Coordinate p10 = mc.pts[start1];
Coordinate p11 = mc.pts[end1];
// terminating condition for the recursion
if (end0 - start0 == 1 && end1 - start1 == 1)
{
mco.Overlap(this, start0, mc, start1);
return;
}
// nothing to do if the envelopes of these chains don't overlap
mco.tempEnv1.Initialize(p00, p01);
mco.tempEnv2.Initialize(p10, p11);
if (!mco.tempEnv1.Intersects(mco.tempEnv2))
{
return;
}
// the chains overlap, so split each in half and iterate (binary search)
int mid0 = (start0 + end0) / 2;
int mid1 = (start1 + end1) / 2;
// Assert: mid != start or end (since we checked above for end - start <= 1)
// check terminating conditions before recursing
if (start0 < mid0)
{
if (start1 < mid1)
{
ComputeOverlaps(start0, mid0, mc, start1, mid1, mco);
}
if (mid1 < end1)
{
ComputeOverlaps(start0, mid0, mc, mid1, end1, mco);
}
}
if (mid0 < end0)
{
if (start1 < mid1)
{
ComputeOverlaps(mid0, end0, mc, start1, mid1, mco);
}
if (mid1 < end1)
{
ComputeOverlaps(mid0, end0, mc, mid1, end1, mco);
}
}
}
public void ComputeOverlaps(MonotoneChain mc, MonotoneChainOverlapAction mco)
{
ComputeOverlaps(start, end, mc, mc.start, mc.end, mco);
}
