[QGIS-Developer] Processing 3.0: Possible change to the Convex Hull algorithm

Nyall Dawson nyall.dawson at gmail.com
Tue Jun 27 15:54:02 PDT 2017

On 28 June 2017 at 05:06, Anita Graser <anitagraser at gmx.at> wrote:
> I absolutely understand the reason from an engineering point. From the user
> point - and as someone answering a lot of user questions - it is predictable
> that end users will be confused.
> Idea: Have a warning if a user tries to run the new "convex hull" on a
> dataset with single part geometries?

Ok - perhaps requiring only multipart feature inputs is too extreme. How about:

1. We drop the field group option, for the same reasons initially
described (there's better algorithms to do this)
2. Add a new boolean option for which creates as single hull for all
features in the layer

Would that work?

Alternatively we could have two algorithms:

1. Convex hull - operates per feature on just the geometry for each feature
2. Layer convex hull - generates a convex hull covering a whole input layer

(By the way - I'm not trying to go full "unix philosophy" here (since
that's a flawed premise anyway!). It's more about dropping/fixing
badly designed options when better alternatives exist).


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