Capturing 3D objects using photogrammetry and Reflectance Transformation Imaging (RTI)
Photographers in cultural institutions have mastered the precision required for creating the highest quality archival images of their collections. They constantly aim higher through developing and researching new techniques and practices, sharing these via professional forums such as the Association for Historical and Fine Art Photography (AHFAP). But you can’t fully appreciate the objects in museums from straight photography alone. The Fitzwilliam Museum recently organised a workshop to explore ways of enhancing interaction with cultural objects.
But this issue isn’t unique to just museums - not everything in the University Library is a flat page, as the Library’s Curious Objects exhibition demonstrated. In order to digitise some of these objects and retain their intrinsic sense of form, there is only one solution – to use photogrammetry to produce a photo-realistic three-dimensional model.
In the past photogrammetry was a complex and painstaking process, but modern technology has revolutionised the process to a point where the time it takes makes it a much more viable option. And so the digital world is no longer flat, and objects such as this pocket globe can now be much more fully appreciated and studied through the resulting 3D model.
This process doesn’t just enhance the viewing experience, but can actually surpass the original object as a tool for studying and researching objects. When a stray cuneiform clay tablet came to light, hiding in a box of medals, at the University Library, it pushed back the date of the earliest written object in the Library by over 2000 years. Cuneiform tablets have long pushed the boundaries of imaging techniques and, indeed, interpreting the cuneiform script was one of the academic drivers in the early years of photography through the work of the likes of William Henry Fox Talbot. But when Professor Nicholas Postgate, a Senior Fellow at the McDonald Institute for Archaeological Research at Cambridge, was asked to take a look at the tablet, he used a 3D model of it to virtually handle and study the object in much greater freedom and detail than would have otherwise been possible.
Academic research into artefacts, such as cuneiform tablets, also led to the development of another imaging technique called Reflectance Transformation Imaging (RTI). This technique creates a detailed visualisation of the textured surface of an object and is sometimes the only way to reveal miniscule surface features. These are created from multiple digital photographs of a subject taken from a fixed camera position but with a light source from many different angles. The final image is mathematically rendered and presents the subject’s surface with varying highlights and shadows.
New approaches to RTI are being developed that provide increasingly outstanding results, allowing detailed measurements and the use of multispectral imaging. The Library’s Digital Content Unit works closely with colleagues at KU Leuven to test and implement RTI solutions for researchers here in Cambridge.
Keywords
3D, Objects, Digitisation, Cuneiform, Museums, Digital, Interaction, photogrammetry, model, Reflectance Transformation Imaging (RTI)
Key People
Dr Paola Ricciardi, Professor Nicholas Postgate, Blazej Mikula, Amélie Deblauwe, Mark Box, Bruno Vandermeulen