Shape from Profiles

This chapter discusses profiles or outlines which are dominant features of images. Profiles can be extracted easily and reliably from the images and can provide information on the shape and motion of an object. Classical techniques for motion estimation and model reconstruction are highly dependent on point and line correspondences, hence they cannot be applied directly to profiles which are viewpoint dependent. The limitations of classical techniques paved the way for the creation of different sets of algorithms specific to profiles. In this chapter, the focus is on state-of-the-art algorithms for model reconstruction and model estimation from profiles. These new sets of algorithms are capable of reconstructing any kind of objects including smooth and textureless surfaces. They also render convincing 3D models, reinforcing the practicality of the algorithm.

Movements of the Mental Eye in Pictorial Space

When an observer is faced with a straight photograph, the observer can either look at the image or look into the photograph. This manner of observing photographs presents a difference that is crucial. In the former case, the observer is aware of the photograph as a physical object in a physical space while in the latter, the observer is aware of the pictorial object in a pictorial space. This chapter focuses on the current understanding of pictorial perception and the structure of pictorial space. Pictorial space is different from physical space in that it does not exist outside of the observer's awareness. It is a thread of consciousness and a purely mental object. In contrast, the photograph as a physical object is a mere planar sheet composed of pigments in a certain simultaneous order. The concepts of pictorial object and scene is not limited to the earlier existence of a physical space that figured casually in the present existence of the photograph. The theory of pictorial space is largely derived from psychophysical data. The measurement of it depends on the idiosyncratic movements of the mental eye. It is purely an ‘intentional entity’ that makes its elusive to physiological methods and susceptible to misconception.

Modelling Sagalassos: Creation of a 3D Archaeological Virtual Site

This chapter discusses the goals of the Murale project, an Information Society Technologies (IST) project, which is funded by the European Commission in order to advance the use of computer technology in the field of archaeology. The Murale project aims to offer solutions on the basis of photo-realistic modelling tools. The creation of the Murale project allowed archaeologists to solve old tasks with new means. This new technology has been applied to the Sagalassos site in the hopes of creating a convincing impression of how this Turkish province developed over the centuries. In this chapter, the focus is on the work carried out by three of the partners of the Murale: ETH Zurich, Eyetronics, and the University of Leuven. The results of their work predominantly pertain to 3D shape acquisition and image-based texture synthesis.

Automatic Creation of Virtual Artefacts from Video Sequences

Digital representation of an artefact is necessary in order to measure, admire and analyse such ancient pieces. For the purpose of storing, recoding and transmitting information, digital photographs may be enough. However, in the examination purposes of an artefact, a 3D presentation is invaluable as it allows the object viewpoint to be modified freely and 3D measurements to be taken on object features. This chapter describes the system by which 3D models from photographs can be acquired, without the need for the calibration of system geometry such as the camera focal length, relative motion of the camera and object, and the relative positions of the camera and object. This system instead computes the representation of all possible objects and camera configurations which are consistent with the given image. The first section discusses how tracking points observed in 2D images allows for the computation of the relative camera and object geometry. The second section discusses the construction of a triangulated 3D model from the object projections. The third section discusses the refinement of the model based on surface texture.

Virtual Reality, Relative Accuracy: Modelling Architecture and Sculpture with VRML

This chapter evaluates current possibilities for the attainment of a realistic context over the web by attempting to match the basic requirements of art history scholarship and teaching against what is currently offered and what can be expected in the future. It surveys some ongoing research in the field from the perspective of an observer and a user. The first section of the chapter discusses virtual reality modelling language (VRML) and describes a project of the Supercomputer Group at the Australian National University. This project aimed to model, using VRML, the Buddhist stupa at Borobudur. The chapter also discusses a second project which deals with the Piazza de Popolo at Rome and the reasons why this project did not employ VMRL. The second section of the chapter examines some other ways in which an ordinary lecturer may use various simple technologies to conjure context, and with more flexibility, detail and accuracy that VRML can ever achieve.

Shadow Stereo, Image Filtering, and Constraint Propagation

It is agreed that stilus tablets are very important documentary sources, however they are the most difficult to decipher. The difficulties in deciphering them is due to the rough surface of the tablets, the low brightness contrast of the incisions, the dense wood-grain lines, and the badly stained and pitted nature of the tablets. All of these posit a challenge for conventional two-dimensional (2D) image analysis. This chapter aims to provide a system that would aid the historian in interpreting stilus tablets by improving the legibility of the tablets. It provides novel ways of determining the texts incised on the tablets. One of these is the use of three-dimensional (3D) image analysis techniques. Such a technique is capable of detecting incisions, compared to the 2D image analysis, and is portable and inexpensive. Another method that can be used is the use of shadow stereo. This method employs low raking angle light close to the plane of the tablet at different elevations. The chapter also discusses the image formation process and the process of choosing elevations for each azimuth direction. The chapter also includes a discussion on realizing the shadow stereo algorithm.

Interpretation of Ancient Runic Inscriptions by Laser Scanning

Traditionally, investigations of runic inscriptions have been conducted in the field by eye, and by feeling the outlines of the runes with fingers. Although photographs have been used to describe runes, they are typically of complementary use. This chapter looks at the interpretation of runic inscriptions through laser scanning. Laser scanning, compared to the old methods of determining runic inscriptions, is more accurate and more efficient. It is specifically important when the interpretation is unclear. This method records the height of surfaces in shades of grey only, hence eliminating disturbances caused by the different colours of the rock. The chapter also discusses how data derived from the measurements of laser scanning can be treated. It provides an account of the application of laser scanning in runic inscriptions in Scandinavia as well as methods that can be used when interpreting runic transcriptions with new techniques.

Reconstruction of a 3D Mummy Portrait from Roman Egypt

This chapter focuses on the reconstruction of the portrait mummy of Hermione, which was excavated in 1911. Hermione lived during the reign of the Roman emperor Tiberius and belonged to the Greek immigrants of ancient Egypt who were descendants of the soldiers who have fought Alexander the Great and the Ptolomies. Hermione is believed to have been a school teacher, as her coffin portrait bears the Greek inscription ‘Hermione grammatike’. To reconstruct the face of Hermione, x-ray imaging processes were first employed to gain vital information without moving the painted cartonnage and wrappings of the mummy. Computed tomography and CT scanning technology was also used to provide a measurement of the 3D distribution of x-ray absorption coefficients throughout the scanned volume. This more advanced form of scanning allowed for the creation of 3D reconstruction of the volume. For the 3D reconstruction of the face of Hermione, four methods were necessary. These were the acquisition of 3D data on what lies inside the wrappings, the 3D reconstruction of the skull, the reconstruction of the soft tissues over the skull, and the application of texture to the reconstructed facial surface.

The Skull as the Armature of the Face: Reconstructing Ancient Faces

This chapter discusses the role of the skull in forming the face and in identifying individuality, particularly in reconstructing ancient faces that bear semblance to the dead. Skulls serve as the armature of the face, where tissue, muscles and the skin are attached to form a distinct face. Whereas a surgeon removes layers of skin and tissue to reveal the skull, a medical artist builds each muscle in the skull by using well-established statistics for the flesh thickness and adds layers of clay for the skin. In general, the reconstruction of the face involves the use of a plaster cast replica of the skull. In such replicas, pegs are inserted to the cast to mark the thickness of the skull. In the whole process of face reconstruction, the skull, the medical and the pathological evidence provided by the skull and the post cranial skeleton dictate the formation of the face. In instances when the skull is absent or inaccessible, portraits found on the coffins are vital for reconstruction. While face reconstruction may seem simple, the process of reconstructing faces is a difficult task. Reconstruction of the face requires painstaking work, and knowledge of pathology, anatomy, dentistry and much more to build a case for history. Nevertheless, the painstaking work of face reconstruction is important in the field of forensics and in medical applications. Some of the cases of face reconstruction described in this chapter include the face reconstruction of Phillip II of Macedon, the face reconstruction of the Great Harwood case, the recreation of the faces of the Grave Gamma and the Seianti.

Italian Terra Sigillata with Appliqué Decoration: Digitising, Visualising, and Web-Publishing

This chapter presents a draft of a long-standing interdisciplinary project involving photogrammetry and archaeology, in which both sides tried to eliminate the gap between their disciplines. This is the Applikensigillata project which aimed to determine appliqué decorations in Italian terra sigillata. The cooperation of the different disciplines resulted in a substantial extension of the timetable. Although the project was relatively time consuming, it nevertheless provided results that were instrumental to archaeology. The project Italian terra sigillata of Noricum produced archaeological results. It produced correct drawings of the appliqué decorations through photogrammetry; it yielded a general catalogue; it opened a new field of results reflecting quality in both shapes and decorations; it debunked the old-myth of the carter-like organisation of Roman; and it eliminated surviving old catalogues based on the observation of a single piece.