[Qgis-user] Reqgis 0.10 slow digitizing with grass

[maning sambale]

> I recommend exporting the "GRASS rgb images" (they are "groups", are
> they?)
rgb image from r.composite, using "groups" to display rasters slows
the render even more.

from GRASS into GeoTIFF with r.out.gdal.sh (if you go for the C
> r.out.gdal counterpart, make sure you run gdal_translate on the output
> to reduce the file size; somehow the C r.out.gdal produces GeoTIFFs
> bigger than gdal_translate can).
Thanks for pointing this out.  (note to self: always run
gdal_translate when exporting gtiffs)

>Build overviews for your GeoTIFFs with
> gdaladdo then (I'd go external overviews - make the GeoTIFF read only
> and then run the gdaladdo on it to achieve this). Overviews should speed
> up their render times much.
Right, thanks!  But, can QGIS build external overviews from native
GRASS rasters?

>> a shapefile.
>
> I'm not sure, but maybe building an index in QGIS can help, ?. And it
> would not harm to process the shapefile with ogr2ogr without parameters
> which might reduce it's size - I happened to notice this works with some
> Shapefiles I got. At worst, even if the shapefile won't render faster it
> will occupy less disk space and might have lower memory footprint.
I'm not editing the shapefile, but creating the index helps a bit.

I think the lag time occurs when editing, saving, re-rendering the GRASS vector.

I removed the raster's for now and it does improve rendering.

cheers,
maning

> Maciek
>
> --
> Maciej Sieczka
> www.sieczka.org
>


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