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Help & guidance Guides to Good Practice

Significant properties

Martina Trognitz, (IANUSDeutsches Archäologisches Institut – DAI), Kieron Niven, Archaeology Data Service.
Valentijn Gilissen (Data Archiving and Networked Services – DANS), with additional contributions from Ruth Beusing (DAI), Bruno Fanini (CNR), Kate Fernie (2Culture Associates), Roberto Scopigno (CNR), Seta Stuhec (OEAW), and Benjamin Štular (ZRC-SAZU), Archaeology Data Service / Digital Antiquity (2016), Guides to Good Practice

As discussed in detail in Section 2 of this guide, the various elements of 3D models – their significant properties or characteristics – can vary considerably and not all file formats support the storage of all 3D data properties. For this reason the selection of a suitable format for archiving needs to consider which properties need to be retained in order to successfully preserve all elements of the model. As highlighted by McHenry and Bajcsy (2008), in many cases file format conversion introduces information loss and it is therefore important to consider the properties of file formats used for archiving during the data creation stage. The following table (derived from McHenry and Bajcsy, 2008) gives an overview of parameters supported by a number of formats discussed in this guide. Empty cells either mean that the format lacks the ability to store these properties or that no traceable specifications for this property/format can be found.

Properties supported by the various 3D formats.

  • Geometry: F = Wire frameP = ParametricCSG = Constructive Solid GeometryB-rep = Boundary representation
  • Appearance: C = ColourX = Texture by imageB = Bump mappingM = MaterialV = Viewport and cameraL = Light sourcesT = TransformationG = Grouping/arrangement

Table 2: An overview of parameters supported by a number of 3D data formats (after McHenry and P. Bajcsy 2008)

Format Geometry Appearance Animation
F P CSG B-Rep C X B M V L T G
X3D
VRML
DAE
U3D
PLY
OBJ
STL
(Binary
only)
DXF

The table above is not exhaustive and there are many additional special properties of 3D content that are used in specific, often proprietary, applications. For this reason, where future native editing or use of the data (i.e. software specific functionality) is required, it is advisable to additionally retain the original files.