Researchers in the School of Fine Arts at the University of New South Wales recently undertook a project to study the use of darkness (shadows) in visual representation in traditional and holographic images. The aim of the researchers was to analyse the role of shadows in three paintings, through the application of three-dimensional holography. Parts of two of the paintings are shown here. The works are by Giotto (1300s), Masaccio (1420s), and da Vinci (1490). The aim of the research was to enable the researchers to transpose the historic use of shadow to a hologram.
Image 1: Baptism of the Neophytes by Masaccio, held in the Chapel Brancacci, in Santa Maria del Carmine, Florence.
Beyond that, however, the researchers were also aiming for a better understanding of how the artists used shadow to create the illusion of three dimensions. On might think the problems trivial - a natural light source and the natural shape of an object combine to produce a pattern of light and dark dictated by optics. Unfortunately, the real behaviour of the artists is more complex than that. Numerous prior studies have been able to demonstrate conclusively that no single light source can account for the pattern of shading in many paintings.
Yet, beyond any argument, the painters were able to give their figures a fully 3D look. More exactly, they were able to crate a shape in a robe with nothing more than the complex use of shadow.
Image 2: Dr John Gage models St Peter in the Masaccio painting for the Cyrax laser scanner..
In order to get a better understanding of the process, the researchers needed to find a way to map the two-dimensional pattern of dark areas on the 3D structure of the model. They approached our group to build a 3D model of one figure painted by each of three of the greatest artists of Renaissance Italy.
The model, eminent art historian Dr John Gage, was attired in drapery with folds, and posed as closely as possible to a figure in on of the paintings. He was then quickly scanned with a Cyrax 2500 3D laser scanner, from two positions, each about four metres away. Each scanner location measured about a million points in the scene and captured 3D co-ordinates of each reflected point. Using two scanner locations enabled the back, front and one side of the model to be seen and measured. This allowed the final holograph to be rotated through about 180 degrees.
Four special control mark targets were placed in the scene and measured from both scanner locations. This allowed the two datasets to be combined (registered) in a process similar to transformations in photogrammetry.
We asked John to stand motionless in the pose while we scanned him from one position and then moved the instrument to te second position and scanned again from there. The results indicate that our model was able to stand still enough to meet the accuracies needed for this project.
A similar procedure was conducted for the three separate attires, each matching one of the paintings.
For each of the three scenes, images were visible in real time as scanning was taking place. The software controlled the measurement process as well as the modelling and analysis of the 3D images. Later processing combined data from the two scanner locations for each scene.
Image 3: Dr John Gage models St Peter in the Masaccio painting for the Cyrax laser scanner..
The Giotto image contains 1,071,962 points. The Masaccio image contains 478,476 and the da Vinci 320,906.
Currently, researchers in the School of Fine Arts are examining the findings. The project will lead to a hologram that wll be seen in an exhibition at the Ivan Dougherty Gallery at the University of New South Wales in September 2003. At that time the public will be able to judge whether or not understanding of how the great men worked will make it possible to imitate them.
