Three-dimensional modelling is an attempt to represent the world in three dimensions,
simplifying through deliberate assumptions. In archaeology, this has developed as
an extension of the traditional use of three-dimensional drawings to help present
and record data. The debate in the archaeological literature over whether surface
or solid modellers should be used is one based on the premise that the purpose of
three-dimensional modelling is data visualisation. This concentration on perception
modelling has been at the expense of research on the modelling of structure. Surface
and Solid Modellers are introduced and defined. I argue that developments in modelling
software mean that there is no longer a clear distinction between the two types of
software along application lines. We should think of models in terms of their applications
rather than the software which generates them. Although data visualisation (including
virtual reality) is an important part of three-dimensional modelling, I argue that
it should be explicitly divorced from the related field of photo-realism at a research
level. Perception modelling can be performed by surface or solid modellers. Modelling
structure is better performed with a solid modeller, if we wish to be as explicit
as possible in our modelling. A structural model can be used as a spatial database.
If we wish to ask questions about the physical properties of a structure, then we
must use solid modellers. In addition to the engineering properties of structures,
solid modellers can also be used to answer questions about the economics of construction.
For historical reasons, the construction industry has preferred to use surface modellers,
but I argue for the advantages of solid modelling in the archaeological study of construction.