qgis - How to smooth large vector polygons from Raster

I have a landuse classification raster file (6 classes) of a large area. But I need it in vector polygons so I vectorised it. No problem so far, but the result is - of course - that every pixel is exactly vertorised with all its egdes :) But I need it smooth like contours. So, okay, I could generalize it with Boyle's Algorithm for instance, but its just too much for my computer to calculate that...

So what could I do? Thanks! Martin

Answer

Use GRASS with the native GUI or with the QGIS plugin or with the Sextante plugin and use the v.generalize tool, choosing the "Chaikens" algorithm.