The outlines are both, for overlyaing for artistic purposes and to select objects for post production. But I'd prefer having the multi pass coloured picture for selecting objects...I tried multi pass mask for Corona already, but somehow it didn't work...2 objects with the same material had different colours when i tried it. Also I had way too many colours, thats why I couldn't really use the mask thing. For my post production I need only a few colours, so I can select all wooden objects fast for example.
I will try the cel rendering! Thanks for advice.