Vectorworks and Document Preferences
There is not a set of preferences that just deal with rendering. There are Vectorworks preferences (effecting all your files) and Document preferences which may have an effect over the look of your rendered views. The Vectorworks Preferences are preferences that affect every Vectorworks file, unlike Document Preferences which are only stored in the current document. You might find that these preferences have already been set, but it is a good idea to check through these to see if these preferences are the way you like.