I have used AutoCAD on and off for the last couple of years and can get most CAD designs completed using it, by hook or crook. Although, not always in the most pleasing of timescales, which really doesn't matter that much as they are generally for non-commercial purposes. 123D Design is a free CAD alternative, although not entirely free, that is also used for 3D modelling.
Today it seems that a lot of the features of AutoCAD have been incorporated into 123D Design. Hence, from what I have read the core engine used to drive AutoCAD is in fact the same one used in 123D Design. To test if this is the case I decided to undertake my next 3D design project using 123D on Mac OS X and make my efforts the subject of this and subsequent posts in this category.