Big polygon in shapefile not shown in 1.8.0

[qgib]

Author Name: Timo Proescholdt (Timo Proescholdt)
Original Redmine Issue: 6449
Affected QGIS version: master
Redmine category:projection_support

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Certain big polygons of a shapefile are not shown correctly in QGIS 1.8.0, while they are shown ok in 1.7.4.
The problem is that while the polygons are displayed when the zoomlevel is low enough, they disappear once the zoomlevel is higher. An additional issue is that the identify feature fails to identify the polygon, even when it is displayed correctly.
The shapefile in question contains a world map. The shapefile can be found here: http://mapbox-geodata.s3.amazonaws.com/natural-earth-1.4.0/cultural/10m-admin-0-countries.zip
The two polygons that are not shown correspond to Russia and Antarctica.

One reason for this might be that both Antarctica and Russia are quite complex polygons, but so is Canada, which is shown ok.

I have tested this on Windows XP and Mac for QGIS 1.8.0, where it does not work, and 1.7.4, where is works ok.

[qgib]

Author Name: Giovanni Manghi (@gioman)

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And what about master, it show with it? I will tag this s blocker as it seems a regression, but please test also master.

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• priority_id was changed from Normal to Severe/Regression
• category_id was configured as Vectors
• status_id was changed from Open to Feedback
• fixed_version_id was configured as Version 2.0.0
• version was changed from master to 1.8.0

[qgib]

Author Name: Richard Burns (Richard Burns)

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I have the sme problem with shapefiles created from "LEICA Geo Office Combined" it applies to all shapefiles, when i zoom in the polygones disapear, this makes digitising and editing these shapes impossible. Shapefiles created in QGis work fine but imported ones that i have surveyed disapear. This is only a problem in 1.8.0 and 1.7.4 works fine so for now i have reverted to 1.7.4

[qgib]

Author Name: Timo Proescholdt (Timo Proescholdt)

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It does not work with master either.
I have installed "QGIS version 1.9.0-Master" (according to "about") via the OSGEOshell.
The problem remains as described above.

[qgib]

Author Name: Giovanni Manghi (@gioman)

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It seems a projection issue, rather than a vector one. Russia and Antarctica polygons cannot be even identified or selected.

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• category_id was changed from Vectors to Projection Support
• version was changed from 1.8.0 to master

[qgib]

Author Name: Werner Macho (Werner Macho)

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Definitely a BLOCKER - confirmed on windows and debian
QGIS 1.8 and master d7a7a46

I don't think it's a projection issue as it works perfectly on 1.7.4..

But where to start searching?

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• operating_system was changed from to Win7 Ubuntu Debian

[qgib]

Author Name: Giovanni Manghi (@gioman)

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• operating_system was changed from Win7 Ubuntu Debian to
• status_id was changed from Feedback to Open

[qgib]

Author Name: Jürgen Fischer (@jef-n)

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Werner Macho wrote:

But where to start searching?

With geometry validity. The shape file contains lots of invalid polygons - eg. russia has 26 errors. I assume it's an upstream problem (GDAL/OGR or GEOS). For instance trying to export an shape from an extent where russia is not shown in qgis (because it only intersects with the current canvas, but isn't completely contained in it) also produces a shape without russia:

$ ogr2ogr -spat 990548.01933083 3581300.99322487 10124463.25272655 8165312.22312922 /tmp 10m-admin-0-countries.shp 10m-admin-0-countries
ERROR 1: IllegalArgumentException: Points of LinearRing do not form a closed linestring

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• priority_id was changed from Severe/Regression to Normal
• resolution was changed from to upstream

[qgib]

Author Name: Jürgen Fischer (@jef-n)

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• fixed_version_id was changed from Version 2.0.0 to Future Release - Lower Priority

[qgib]

Author Name: Médéric RIBREUX (Médéric RIBREUX)

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Hello, bug triage...

in QGIS 2.13 master, I can display the shapefile but at certain zoom levels, some polygons are not rendered.
I can't identify some polygons (Russia and Antartica) but as Jürgen said, this seems to be a problem of invalid geometries.

I suggest we close this bug as this is much more a problem of invalid geometries than a problem in QGIS...

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• status_id was changed from Open to Feedback
• resolution was changed from upstream to

[qgib]

Author Name: Giovanni Manghi (@gioman)

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cleaning the vector (v.clean/st_makevalid/etc.) gives a vector that works as expected.

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• status_id was changed from Feedback to Closed
• resolution was changed from to up/downstream