• A model is used to mathematically capture some aspect of the real world so that it may be manipulated, studied, tested, etc.


• To computerize a design we will capture a very explicit model of a part in a computer program.


• Geometry is by far, the most important part of any design. It is used as a reference for tolerances, processes, functions, materials, assemblies, etc.



• Three major functions in geometric modelling,



• The Geometric Representation determines what a system can do.


• There are a number of methods of representing geometry, 1D, 2D, 2.5D, 3D

2D - All in one dimension, such as a side view of a part

2.5D - Points have an x, y coordinate, and height. This is a special case which can describe raised surfaces like buildings.

3D - Full spatial dimensions



• 2D models are quickly becoming obsolete, 2.5D models were an early compromise, but 3D models are quickly becoming the standard.