Google Sketchup 3D

Google Sketchup is the biggest secret to getting full render-able 

3D animation Architectural designs (Without buying extremely expensive modeling software).

Here is another big secret with Google SketchUp 3D warehouse (everything is here - you don't have to design

appliances, furniture, accessories, etc... from sketch).  In most case, Google Sketup 3D - is all you need for city world building.  This software is cheaper but can play with and against the big boys too.     

This Software objects and scenes can be exported to other 3D animated software too.  Some people buy some 3D software brands - just because of the huge archive of simple objects, refrigerators, tv, appliances, people, street signs, etc... these simple objects are exportable too.   

The daz3d studio is another cheaper universal 3D animation software that allows you to export/import most universal objects and scenes too.  This may allow you to export between any brand 3D Animation Software.  If you create animation models that crash & fail during import/export to other compatible brands - there is a possibility that you may not be simplifying your 3D models - which may cause complex rendering problems or slowness in the future.  Example, If you build a 3D animated car with full details internal and external - it may be wise to animate car scenes with only the car shell, instead of a car with internal complex details.  Occasionally, it does not hurt to have a picture of a car dashboard overlayed on a flat panel inside - instead of full instruments - when animating at a distance.  All this reduces rendering time, and make better performance and fewer glitches.