I'm using Arcmap 10, I need to create a raster from contour lines. These contour lines were clipped out with a certain shape with the purpose to modify them only within that shape and then create the raster from these modified contour lines. The problem is that when I come to the TopoToRaster step, the resulting raster is rectangular, while I'd need it with the shape I used for the clipping. How can I do this? Should I change some options in the Spatial Analyst? How?