The ordering was made to allow determining the "depth" of subgraphs which
are nested within other graphs. This corresponds to a situation where the
buffer creates holes within polygons and polygons nested within holes.
When a disjoint graph is encountered, a stabbing line is constructed from
the righmost segment, and all segments in other subgraphs which intersect
this are found. The minimum one is then computed - this is what the
ordering is used for.
By linear ordering I really mean a total ordering of segments which:
(a) determines the leftmost segment in a set
(b) obeys the general contract for Comparator.
LineSegment#compareTo satifies (b), but not (a) (it's just a lexocographic
ordering by endpoint, which doesn't handle the case where the segments lie
"close together" (i.e. their envelopes overlap). For instance, the
following ASCII diagram shows a situation where A is left of B but would be
greater than B under the LineSegment order:
| /
A | /
/
/ B
/
On Thu, Feb 5, 2015 at 1:47 PM, Michael Michaud <[email protected]
> wrote:
> Hi Martin,
>
> The DepthSegment compareTo still does not obey the contract,
> unfortunately. It's difficult to come up with a consistent linear ordering
> for 2D segments.
>
> It would be great if someone can build this and give it a test with real
> data.
>
> What is this ordering made for, and what do you mean by linear ordering ?
> Isn't LineSegment#compareTo method enough to get a strict ordering over
> segments for example ?
>
>
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