3.3 Technical considerations

Blender was chosen as the main software to be used for the modelling for a number of reasons. Firstly, Blender is free, which is especially important given the comparatively large cost of its competitors; Lightwave, Maya and 3D Studio Max. Its open source licence and ability to be easily expanded ensures a steady stream of updates created by the user community. Although its functionality and output are not yet directly comparable to other packages, it is catching up quickly and already contains enough functionality for the relatively simple demands this project placed on it. Blender's ability to interface with a variety of renderers also allows it more flexibility in illumination realism. Disadvantages include an inconvenient method of transfer from AutoCAD and a lack of measuring tools, meaning that some measurements are more conveniently done using the original DWG file. This is compounded by the fact that Blender works in Blender Units rather than any definite measuring system. For the purposes of these models, one Blender Unit equals one metre. The project was started using Blender v2.41 but continued up to v2.45, utilising the increased toolset of the newer versions.

Stages involved

The initial data were taken from a file in DWG format created by the AAPP's surveying team of Alvin Ho, Eric Poehler and Arthur Stephens. The file was a composite of a series of sessions with a Leica 307 TSR Electronic Distance Meter (EDM) in the insula over the space of three field seasons from 2003 to 2005. The data were downloaded from the EDM every day and the points were joined into one coherent model containing 78 layers. Only the points representing the base of walls were used owing to the necessity to convert to DXF format; converting all 70,000+ points created a file far too unwieldy to use. The resulting DXF file of wall bases was transferred into Blender as a template to trace around. As the file contained a model of the site as it is now, not how it was in antiquity, the AAPP data was squared off to create regular walls. The lack of plaster on many of the walls results in them having a much less regular appearance in the EDM model than they would have had in antiquity.

Height information was derived from the original DWG file in AutoCAD using the ruler feature, enabling the doorways to be projected straight upwards rather than relying on the irregularities inherent in the DWG file. The House of the Surgeon presents a relatively easy modelling task in that the floor levels were almost identical, the exceptions being room 2, which lies 0.3m below and rooms 3 and 4 which are 1m below the others. For this reason I placed the floor level of all floors except these rooms at 0 on the z axis. This enabled easier calculation of heights. Once a base model had been created with the walls, floors and doorways in appropriate positions the construction of the models diverged depending on the purpose for which they would be used.


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Last updated: Tues Feb 5 2008