Hi Jukka,
The original version of the one that creates linestrings from the
selection is from SkyJUMP, and this is as it was designed. However, I have
no objection to changing it to produce a polygon. We used it as a visual
aid to determine line-of-sight between features, but this is not typical.
The interface does not distinguish the most important difference between
the two implementations of convex hull: algorithm. The one with the layer
input uses JTS and the "Graham Scan", the other uses the "Package Wrapping"
algorithm with enhancements. Graham Scan has a better worst case
performance, so it might be better to combine the two functions as we did
with Buffer and use the JTS algorithm in both cases.
regards,
Larry Becker
On Mon, Jun 4, 2012 at 1:42 AM, Rahkonen Jukka <jukka.rahko...@mmmtike.fi>wrote:
> **
> Hi,
>
> Operation "Create convex hull" for a layer creates a polygon while convex
> hull for selected features makes a linestring. This is perhaps a bug and
> against the definitions of
> http://www.vividsolutions.com/jts/javadoc/com/vividsolutions/jts/algorithm/ConvexHull.html
>
> For reproducing, create a new layer, digitise a polygon, select it and do
> Tools - Analysis - Convex Hull and have a look at the resulting geometry.
>
> -Jukka Rahkonen-
>
>
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