The generation of the RTI image requires a set of photos acquired from the same point of view, where in each photo the object is illuminated by a light source from a different direction.

Visual Computing Lab designed and made a light dome for RTI acquisition. Its diameter is 1m and it is composed by four aluminium shells that can easily assembled and disassembled to simplify the transport. Each shell has 29 high power LEDs: 6.4W cold white light (5600K) without UV and IR componets and 685 lumen (124 lm/W).
The device is completed by an eletronic central unit based on the microcontrolled board Arduino that manages the LEDs, the overhead support to mount the reflex camera (in our case NIKON D5200, 24Mpixel) and the software that synchronizes the shutter of the camera with the swithing on of each LED. The acquisition is computer-automated and takes about 5 minute to capture 116 photos. Using a macro lens the dome is able to acquire a subject area between 3 cm and 30 cm. The dome has been used for the digitization of a selected subset of the coin collection of the Museum Palazzo Blu in Pisa to produce high quality RTI images for each face of the coins.

When the acquisition with a physical dome is not possibile for the size or the location of the object, it is possibile to manually place the light source in different position around it forming a virtual illumination dome. The light placement can be decided before the acquisition in a planning step, which, using the data on the size and location of the object, produces the position where to place the light source, or during the acquisition using a glossy sphere to track the light movement. In the second case after the capture session a software is able to extract the light direction of each photo by segmentation of the highlight produced by the light on the glossy sphere.

The tool RTIBuilder to create the RTI image from the set of acquired photos is available at the following link.


Storytelling of a Coin Collection by Means of RTI Images: the Case of the Simoneschi Collection in Palazzo Blu
Gianpaolo Palma, Monica Baldassarri, Maria Chiara Favilla, Roberto Scopigno Museums and the Web 2014 - February 2014

High Quality PTM Acquisition: Reflection Transformation Imaging for Large Objects
Matteo Dellepiane, Massimiliano Corsini, Marco Callieri, Roberto Scopigno The 7th International Symposium on VAST International Symposium on Virtual Reality, Archaeology and Cultural Heritage, page 179--186 - November 2006