i am trying to select grids (polygon geometry) that intersected with building layer. i can do it by using "select by location" tool. and then i generate centroids from the selected grids. there is no problem in this steps. later i generated a model with sextante modeler but it doesnt work properly. select by location tool dosnt work in sextante modeler. it cannot select features. interesting that i can run perfectly this tool directly from sextante toolbox !!! so i need your idea that how can i extract the grids that interseced with another layer.