Line Offset in symbology generates artifacts

[qgib]

Author Name: mathieu rajerison (mathieu rajerison)
Original Redmine Issue: 9485
Affected QGIS version: 2.0.1
Redmine category:symbology

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Line offset in symbology is useful when you have a network with several lines superimposing with others.

But it generates artifacts.

The problem is less visible as the scale is getting bigger.

The problem is also encountered when merging all the lines in a single line.

In the attached file, you have the result with offset and without.

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• qgisLineOffset.jpeg (mathieu rajerison)
• pb_qgis.jpeg (mathieu rajerison)
• issue_9485-results.JPG (Alvaro Huarte)

[qgib]

Author Name: Alvaro Huarte (@ahuarte47)

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This may be due because "simplification" of geometries is enabled.

You can disable it -> Layer properties -> Rendering -> un-check "Simplify Geometry"
Or settings -> options -> rendering -> un-check "Enable feature simplification by default"

[qgib]

Author Name: mathieu rajerison (mathieu rajerison)

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I am under QGIS Dufour and I can not see none of these options.

In layer properties, does rendering refer to "Style". If yes, I can not see "Simplify Geometry"
In the settings > ... > Rendering, I can not see any mention to feature simplification..

[qgib]

Author Name: Nyall Dawson (@nyalldawson)

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This relates to #18048

[qgib]

Author Name: Alvaro Huarte (@ahuarte47)

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mathieu rajerison wrote:

I am under QGIS Dufour and I can not see none of these options.

In layer properties, does rendering refer to "Style". If yes, I can not see "Simplify Geometry"
In the settings > ... > Rendering, I can not see any mention to feature simplification..

My apologies for the confusion, You are right, the simplification will be released in 2.2.
Alvaro

[qgib]

Author Name: mathieu rajerison (mathieu rajerison)

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Hi,

I took note that a similar issue had already been opened.

Here is a snapshot with and without simplification and with and without offset, just for illustration.

The object is a single line.

Mat

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• 6740 was configured as pb_qgis.jpeg

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• pb_qgis.jpeg (mathieu rajerison)

[qgib]

Author Name: Giovanni Manghi (@gioman)

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There is no crash or data corruption, so I'm lowering the priority.

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• category_id was configured as Symbology
• priority_id was changed from High to Normal

[qgib]

Author Name: Giovanni Manghi (@gioman)

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duplicate of #18048

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• status_id was changed from Open to Closed
• resolution was changed from to duplicate

[qgib]

Author Name: Alvaro Huarte (@ahuarte47)

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This pull request ( #1205 ) improves the offset of lines using GEOSOffsetCurve if GEOS 3.3 is available.

Results:
!issue_9485-results.JPG!

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• 6836 was configured as issue_9485-results.JPG

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• issue_9485-results.JPG (Alvaro Huarte)