I have a problem with the GRASS module r.sun when I run it in QGIS. I would calculate the hours of insolation in a specific site during a specific day. When I ran the algorithm "r.sun" from GRASS, it works very well, but when I launch the same algorithm from QGIS toolbox the result is different and not so realistic. Do you know if any specific setting is needed in order to run correctly the algorithm also in QGIS? Is it a problem of region definition?