Photogrammetry and 3D Imaging; Bridges Collection: 123D Catch

By Sophia Mirashrafi

This past August, I was given the opportunity to work closely with the Bridges Collection through the continuation of the 3D scanning project. It was my aim to discover a quicker way to scan these artefacts on the computer, and to make them more accessible to the public online.

selection of objects from the Bridges collection

Although it produces excellent results, the previous photogrammetry project was also very time consuming, and so I made it my goal to find something that was more efficient. After some research, I decided to look into a simpler version of 3D imaging in the form of 123D Catch.

The premise is simple: I simply placed the artefact on a turn table, and took 30-40 pictures of it, rotating the object slightly after each photo. The aim here was to take pictures of the artefact from multiple angles with as many redundancies as possible. This way, the software in 123D Catch was able to recognize and match corresponding features in each different shot, and be able to piece together a 3D image as soon as you plug your photos into the software.

working with images in 123d catch

Depending on the amount of photos used, the whole process from the initial pictures to the rendering takes about 20-30 minutes maximum. I would usually take the photos of an object, plug them into the programme, and begin the next artefact while the last was rendering. I used my Canon Rebel to take the pictures, but could have easily have used an iPhone.

This method is extremely quick and for the most part quite successful. Some challenges that it presented was the fact that it did not include the bottom of the artefact in the scan. In the previous project, the artefact could be turned in all directions, while in 123D Catch, it instead only captures the object as it would be seen on a flat surface. It therefore lends itself wonderfully to artefacts like bowls and standing figurines. However, for artefacts such as the terracotta bell, which was captured in the preceding project, this limitation causes the final project to miss details which aid in its identification. To see what I’m referring to, please compare the first project and the second by following these links:

Beyond establishing another technique of photogrammetry, the primary aim of this project was to allow the collection to be as accessible to as many people as possible. The Bridges Collection is truly a fantastic collection of artefacts that encompasses a significant range of Cyprus’ history. As of now, these treasures lie in a quiet corner of the School of Classics, +-where only a handful of students and visitors have access to them. Out of those even fewer are able to examine them in detail out of the cases. The beauty of 3D modelling and the move to put these resources online is that it makes it not only more accessible to the St Andrews community, but to anyone who has access to the internet and the inclination to learn about it.

123D Catch is free to download and to use. Take a look at my page to see some of the artefacts that I’ve already scanned. http://www.123dapp.com/MyCorner/ssm9-26457812/models

image3

This project is not yet finished, however. Now that an efficient method of photogrammetry has been established, I am going to work at representing the rest of the collection online. After this is underway, more specific exhibits can be created using this growing archive of images and 3D models. By drawing on this online archive, students can highlight the connections and similarities of this diverse collection beyond their current chronological display. Themes such as domestic life, funerary practices, and manufacturing can highlight hidden aspects to this fascinating and eclectic collection of artefacts. This is an extremely worthwhile project, bringing the St Andrews Bridges Collection into the digital age.

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The Bridges Collection

By Catherine Cruickshank

From January – August 2014 I selected a range of Cypriot artefacts from The Bridges Collection for 3D scanning and modelling, held in the School of Classics, University of St Andrews.   This was an experimental project conducted in collaboration with the School of Classics, Computer Science and Museum Collections, which formed the basis of my project for the Mlitt in Museum and Gallery Studies. The project was carried out with the aim of broadly representing the chronology of the collection. However, just as importantly, the method of scanning – using a 3D laser scanner was also part of the experimental process. It was not known how well this method would work or what types of materials or shapes and colours/decorations would scan well.

Using a portable NextEngine 3D laser scanner, provided by the School of Computer Science, I carried out test scans on objects to learn how to use the machine. Once I felt comfortable with it, I began to choose objects from the collection.

image1 - object in the 3D scannerThe Bridges Collections spans several cultural periods of Cypriot Archaeology and I hoped to have representative scans from each of these – Bronze Age, Iron Age, Roman and Byzantine. I found that terracotta objects with a contrasting painted decoration scanned very well. The collection holds several figurines which scanned beautifully including a halo plank figurine and a small anthropomorphic ornamental bell.

halo plank figurine     anthropomorphic ornamental bell

The Roman artefacts such as a small lamp and small bottles scanned well due to the nature of the material. The Byzantine collection of Sgraffiato Ware also scanned well, despite my concern that glazed objects would be too shiny for the lasers and therefore too reflective.

Sgraffiato Ware

Each scan took anywhere between 30 minutes and 1 hour depending on the level of detail. For example, deeply carved objects such as a stone head took a great deal of time.

Scan of stone head

Each object also required at least 2 scans at different angles in order to capture the whole of the object, inside and out. What I discovered was that, the more scans required to complete an object, the larger the file, and consequently they became difficult to view online. The various scans for an object were then aligned together using virtual pins in the NextEngine software, Scanstudio.

aligning two scans of an object

Once ten objects were scanned, they were loaded into WebGL by the Open Virtual Worlds team and placed on the server so that I could create links to the images from the webpages I then created.

The experience of using the scanner was an interesting and challenging one. As one of several options for creating 3D models of objects it has proved that an object can be scanned in depth and that different angles can be scanned in order to provide a complete image. Unfortunately, the downside of this method of 3D scanning is that the files created are quite large and therefore, when it comes to placing them online, only the fastest and most up to date browsers will support the scans. The aim of accessibility was somewhat thwarted by this. However, it was successful in that clear images were created and the continuing work with various other methods of 3D modelling such as photogrammetry are proving to be more successful in providing ready access to virtual collections.

The scans can be viewed on the Bridges Collection website:  https://arts.st-andrews.ac.uk/bridges-collection/

Digital recreation: small scale

The School of Classics is pleased to announce the launch of a new project website, displaying 3D scans of objects from the Bridges Collection.

With guidance from Rebecca Sweetman, Iain Oliver and Jessica Burdge, Cathy Cruikshank undertook the project as part of her studies on the Museum and Galleries Studies MLitt programme. Currently, there are ten items on display, and Cathy hopes she can publish more over the next few months with support from the Open Virtual Worlds team.

carved-head-silhouette