[Qgis-developer] Sextante test drive

Tim Sutton lists at linfiniti.com
Sat Apr 20 13:37:16 PDT 2013

Hi Diego

Can I suggest to put your post in a new thread instead of
incorportating it into an existing (and unrelated to your post)
thread? I suspect many people who may have given you feedback will
have missed your message unless they were following the sextatnte
testdrive discussion.



On Sat, Apr 20, 2013 at 4:12 PM, Diego Gnesi Bartolani
<diego.gnesi at gmail.com> wrote:
> Hi,
>     I am an italian archaeologist and an enthusiastic QGIS user. I do
> what I can to spread the knowledge about QGIS and other open source
> softwares to my university students (I am a contract professor at the
> Basilicata University and some days ago I've become contract professor
> at the Specialization School of Archeology of Udin, Venice and
> Trieste).
> The main difficulty I have with open source GIS is the advanced
> editing of vector layers. QGIS doesn't offer too much support to
> digitizing, the CAD Tools plugin has some useful functions but is far
> from being complete and the kind of interaction that it proposes is
> not very productive and time-saving (it's not a critic: CAD Tools
> saved my life a lot of time, and I want to thank the developers and
> maintainers). Many times, I had to convert my vector layers to dxf and
> back in order to perform some complex tasks (with all kind of
> conversion problems, like the preservation of the attributes values,
> etc.).
> I have some experience in programming (about ten years of
> developement, mainly in C# with the .NET Framework, before I switched
> to Linux), and I would like to try (only try, without promising
> anything!!) to implement complete CAD tools and functions (I there
> isn't and analogous project already active; in that case, nevermind!).
> I think that developing a CAD plugin from scratch is very hard to me
> and maybe not the better way to get good results, so I'm oriented to
> try to augment the interaction between QGIS and an existing CAD
> software (I'm thinking to LibreCAD). I thought to two possible
> strategies:
> 1. Use the LibreCAD library and source code to develop a C++ QGIS plugin;
> 2. Create a shapefile/spatialite/postgis driver for LibreCAD in order
> to edit those formats inside LibreCAD.
> 3. Convert some layers of the QGIS project in a dxf file and back
> (each QGIS layer in a different layer of the final dxf file).
> I'm asking your opinion about which of those ways could be the faster
> or the better to implement, or which one is impossible to undertake
> according to your knowledge of the QGIS API.
> My doubts are:
> Strategy #1: Probably the ideal one, but does the implementation of
> complex snaps or constraints against the features of other layers
> (i.e. midpoint, parallels, etc.) require changes to the QGIS API, or
> all these operations can be contained on a plugin? Is it better to
> work directly on QGIS vector layers or to create a plugin layer, edit
> it and then commit the changes to the vector layer? The conversion
> could help me to manage geometries in the way LibreCAD wants. Is it
> possible in your opinion to have an interactive shell (i.e. draw the
> first point, and then inserting the coordinates of the second point)?
> Strategy #2: Probably the easier, but I should find a way to disable
> some LibreCAD functions (i.e. the drawing of splines, or the drawing
> of points on a line layer) without disseminating my changes all over
> LibreCAD's source files. For this kind of solution I'll ask to the
> developers of LibreCAD.
> Strategy #3: The problem is on committing the changes of the dxf file
> to the original layer: how to specify that a line in the dxf file must
> replace the geometry of and existing record of the original spatialite
> layer? Maybe it's impossible, it doesn't seem to me that I can put on
> a dxf file the necessary metadata to preserve a link to the original
> features.
> What do you think? And what do you actually do when you have to draw
> complex shapes on shapefiles or other vector layers?
> Diego Gnesi
> 2013/4/20 Paolo Cavallini <cavallini at faunalia.it>:
>> Hash: SHA1
>> Il 20/04/2013 10:52, Victor Olaya ha scritto:
>>> I have been thinking about changing all the options dialog. Doesn't
>>> look hard to do, so you can count on having this ready soon
>> great, thanks. ready to help if necessary. I still think the appearance of sextante
>> dialogs do not seem too much in line with QGIS look, so maybe you can ask someone to
>> help with the GUI.
>>>    1) The classification of algorithms is done manually...and it is
>>> boooooring to do :-) SAGA and QGIS ones are already done, but I have
>>> to do the GRASS ones. However I am not sure about including GRASS, it
>>> is more complex to use. You can use a SAGA algorithm without knowing
>>> what SAGA is, but to use a GRASS one, you need to understand some
>>> GRASS ideas, so it is an advanced process, and the simplified
>>> algorithm classification shouldn't assume that. You can always change
>>> to the advanced view to use GRASS (now you can change directly from
>>> the toolbox, no need to go to the config dialog)
>> Sorry I do not agree with you:
>> * most GRASS commands, as they are incorporated into sextante (or in the GRASS
>> plugin, by that way) are really straightforward to use; in courses people often do
>> not notice the difference
>> * more importantly: GRASS is included in most if not all QGIS installation, so you
>> can rely on it; this is not the same for SAGA
>> * GRASS modules have a proper manpage, while SAGA is sometimes very hard to understand
>> * GRASS has a long history and a wide community, so you can trust more on it on the
>> longer term.
>> So in short I would not put GRASS as a second class citizen in Sextante ;)
>>>    2) I would like to have in that list, only those algorithms that
>>> need no extra configuration, to make that the default and have it
>>> working out-of the box. That's why R and OTB, for instance, are not in
>>> there.
>> Again, do not agree: some OTB commands are very straightforward, and solve problem
>> people have struggled on for years. The usual effect of showing it is jaw-dropping.
>> Removing stuff from first sight may have deeper consequences than a clever developer
>> can foresee, sometimes :)
>>> good idea. If OTB goes into osgeo4w, I could add the OTB algorithms to
>>> the simplified list of algorithms
>> OTB *is* already on osgeo4w - my suggestion (a strong one BTW) is to include it in
>> the standalone installer for QGIS 2.0
>>> I still have to send Jurgen the SAGA package as we discussed it in the
>>> Hackfest. We can put both SAGA and OTB, and taht would really give a
>>> lot of power to SEXTANTE
>> Right!
>> Thanks for your hard work, and good code.
>> - --
>> Paolo Cavallini - Faunalia
>> www.faunalia.eu
>> Full contact details at www.faunalia.eu/pc
>> Nuovi corsi QGIS e PostGIS: http://www.faunalia.it/calendario
>> Version: GnuPG v1.4.12 (GNU/Linux)
>> Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/
>> /6QAoLUqOAhrTP1Rho0PWYfPVVzjyQJr
>> =cHRR
>> -----END PGP SIGNATURE-----
>> _______________________________________________
>> Qgis-developer mailing list
>> Qgis-developer at lists.osgeo.org
>> http://lists.osgeo.org/mailman/listinfo/qgis-developer
> _______________________________________________
> Qgis-developer mailing list
> Qgis-developer at lists.osgeo.org
> http://lists.osgeo.org/mailman/listinfo/qgis-developer

Tim Sutton - QGIS Project Steering Committee Member (Release  Manager)
Please do not email me off-list with technical
support questions. Using the lists will gain
more exposure for your issues and the knowledge
surrounding your issue will be shared with all.

Visit http://linfiniti.com to find out about:
 * QGIS programming and support services
 * Mapserver and PostGIS based hosting plans
 * FOSS Consulting Services
Skype: timlinux
Irc: timlinux on #qgis at freenode.net

More information about the Qgis-developer mailing list