[postgis-tickets] [PostGIS] #3712: Address MVT issues reported by specification author

[PostGIS]

#3712: Address MVT issues reported by specification author
----------------------+----------------------------
  Reporter:  strk     |      Owner:  Björn Harrtell
      Type:  defect   |     Status:  new
  Priority:  blocker  |  Milestone:  PostGIS 2.4.0
 Component:  postgis  |    Version:  trunk
Resolution:           |   Keywords:
----------------------+----------------------------

Comment (by flippmoke):

 @Björn Harrtell:

 It deals with extremely bad geometries, it would can definitely deal with
 the bowtie example. The "fuzzer" I am using basically picks random points
 for a ring, which basically creates a mass of intersections.

  [[Image(https://cloud.githubusercontent.com/assets/1794907/23220907
 /0b6e1b5a-f8e9-11e6-9744-ac4f0a81749f.png, 300px)]]

 Wagyu then will make this completely valid OGC output, including dealing
 with chains of holes that should resolve into new rings etc.

 [[Image(https://cloud.githubusercontent.com/assets/1794907/23220918/138ef714-f8e9-11e6
 -9cdd-1025e2aec538.png, 300px)]]

 The latest released version of Wagyu surpassed ~25 million of these tests
 with out any failures, before I simply stopped the fuzzer.

 @dbaston:

 > If a user wants to store invalid geometry and doesn't care to inspect
 how it's been auto-corrected, it should be easy enough to run
 ST_AsMVT(ST_MakeValid(geom)), no?

 Please see:
 https://github.com/mapbox/vector-tile-
 spec/issues/58#issuecomment-173717621

 In general - clipping, simplification, and scaling can all turn a valid
 geometry into an invalid one as per the specification.

--
Ticket URL: <https://trac.osgeo.org/postgis/ticket/3712#comment:21>
PostGIS <http://trac.osgeo.org/postgis/>
The PostGIS Trac is used for bug, enhancement & task tracking, a user and developer wiki, and a view into the subversion code repository of PostGIS project.