[Qgis-developer] GRASS Direct

[Larry Shaffer]

Hi John and Radim,

On Mon, Dec 10, 2012 at 1:53 PM, John C. Tull <jctull at gmail.com> wrote:
> On Dec 10, 2012, at 12:44 PM, Radim Blazek <radim.blazek at gmail.com> wrote:
>
>> The GRASS Direct is an environment developed within QGIS GRASS
>> plugin/provider which makes it possible to run GRASS raster modules
>> without GRASS mapset and without data conversion to GRASS format.
>> Basically it is a library implementing GRASS data read/write function
>> which is using QGIS providers to read/write data. In direct mode, the
>> GRASS modules are run with this library instead of  the standard GRASS
>> gis library.
>>
>> The GRASS modules may be run in direct mode from GRASS Tools (which
>> are now always enabled) if no mapset is opened. The interface is
>> similar to the standard GRASS Tools apart that the region is selected
>> in combo box in top of options (to be discussed) and the output is a
>> GeoTIFF file. It is also possible to run GRASS modules in direct mode
>> from a shell if some environment variables are set. You can see those
>> variables printed in top of the output tab.
>>
>> This is work in progress, so I was reluctant to announce that but
>> because it had caused some compilation problems, it was necessary to
>> explain a bit how it works. Currently there are only few modules
>> enabled and you can find various problems. Especially it was only
>> tested on Linux and most probably more fixes will be necessary on Mac
>> and Windows.
>>
>> I believe that GRASS Direct could also be used in SEXTANTE with a
>> little work. It would be necessary however to distinguish modules
>> which may be run in direct mode from those which may not (mostly
>> vector modules).
>>
>> Sorry for the problems I caused on Mac and Windows and many thanks to
>> Jürgen and Larry for fixes.
>>
>> Radim
>
> Hi Radim,
>
> This is a great new addition to QGIS, so thank you for you work on it.
>
> I wanted to bring my comment I made elsewhere on my Mac testing into this, more appropriate thread:
>
> I just tested one of the available modules on a local DEM file, and here is there error message that appeared when I ran it:
>
> Cannot start module r.slope.aspect
> command: /usr/local/Cellar/grass/6.4.2/grass-6.4.2/bin/r.slope.aspect --interface-description
>
> ERROR: GISRC - variable not set
>
> Note that I am running a version of grass installed locally, not from the application that William makes available.

Radim, awesome stuff! Thanks for the introduction on it. Looking
forward to using this inside of SEXTANTE.

Getting the same thing as John here, but with Kyngchaos.com GRASS.
When using the Kyngchaos.com GRASS, the app starts via an internal
shell script that configures most of those GRASS env variables [0].

John, again we Mac users are up against shell environment not being
transferred into QGIS. I really think having a spot in the app
preferences to allow manually added/augmented env variables (like
PATH, etc.) would be very handy indeed.

It could be kinda like setting up a build environment inside of
QtCreator [1]. The nice thing about having such an env variable editor
(besides setting up custom variables) is that it would allow both C++
and Python components to inherit the env settings. Example: thereby
giving SEXTANTE access to any custom external install location on the
filesystem.

Note how slim the default passed environment is for Mac GUI apps in
[1] (nothing like my .bash_profile, etc.).

I really think this needs addressed (especially for Mac users), and
could benefit all platforms with further start up environment
customization.

Regards,

Larry

[0] http://grass.osgeo.org/grass64/manuals/variables.html
[1] https://dl.dropbox.com/u/4058089/qgis/env-vars_like-in-qtcreator.pn


> Cheers,
> John
>
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