Polynomial

texture mapping Texture mapping is a term used in computer graphics to describe how 2D images are projected onto 3D models. The most common variant is the UV unwrap, which can be described as an inverse paper cutout, where the surfaces of a 3D model are cut ap ...

(PTM), also known as Reflectance Transformation Imaging (RTI), is a technique of

imaging Imaging is the representation or reproduction of an object's form; especially a visual representation (i.e., the formation of an image). Imaging technology is the application of materials and methods to create, preserve, or duplicate images. ...

and interactively displaying objects under varying

lighting Lighting or illumination is the deliberate use of light to achieve practical or aesthetic effects. Lighting includes the use of both artificial light sources like lamps and light fixtures, as well as natural illumination by capturing daylight. ...

conditions to reveal surface phenomena. The data acquisition method is Single Camera Multi Light (SCML).

Origins

The method was originally developed by Tom Malzbender of

HP Labs HP Labs is the exploratory and advanced research group for HP Inc. HP Labs' headquarters is in Palo Alto, California and the group has research and development facilities in Bristol, UK. The development of programmable desktop calculators, ink ...

in order to generate enhanced

3D computer graphics 3D computer graphics, sometimes called Computer-generated imagery, CGI, 3D-CGI or three-dimensional Computer-generated imagery, computer graphics, are graphics that use a three-dimensional representation of geometric data (often Cartesian coor ...

and it has since been adopted for

cultural heritage Cultural heritage is the heritage of tangible and intangible heritage assets of a group or society that is inherited from past generations. Not all heritages of past generations are "heritage"; rather, heritage is a product of selection by socie ...

applications.

Methodology

A series of images is captured in a darkened environment with the

camera A camera is an instrument used to capture and store images and videos, either digitally via an electronic image sensor, or chemically via a light-sensitive material such as photographic film. As a pivotal technology in the fields of photograp ...

in a fixed position and the object lit from different angles (Single Camera Multi Light). Interactive software processes and combines the set of images to enable the user inspecting the object to control a virtual light source. The virtual light source may be manipulated to simulate light from different

angle In Euclidean geometry, an angle can refer to a number of concepts relating to the intersection of two straight Line (geometry), lines at a Point (geometry), point. Formally, an angle is a figure lying in a Euclidean plane, plane formed by two R ...

s and of different

intensity Intensity may refer to: In colloquial use * Strength (disambiguation) *Amplitude * Level (disambiguation) * Magnitude (disambiguation) In physical sciences Physics *Intensity (physics), power per unit area (W/m2) *Field strength of electric, m ...

wavelength In physics and mathematics, wavelength or spatial period of a wave or periodic function is the distance over which the wave's shape repeats. In other words, it is the distance between consecutive corresponding points of the same ''phase (waves ...

s to illuminate the surface of artefacts and reveal details. Open-source tools for processing the captured images and publishing the resulting relightable images on the web are freely available.

Applications

Polynomial texture mapping may be used for detailed recording and documentation,

3D modeling In 3D computer graphics, 3D modeling is the process of developing a mathematical coordinate-based Computer representation of surfaces, representation of a surface of an object (inanimate or living) in Three-dimensional space, three dimensions vi ...

edge detection Edge or EDGE may refer to: Technology Computing * Edge computing, a network load-balancing system * Edge device, an entry point to a computer network * Adobe Edge, a graphical development application * Microsoft Edge, a web browser developed b ...

, and to aid the study of inscriptions,

rock art In archaeology, rock arts are human-made markings placed on natural surfaces, typically vertical stone surfaces. A high proportion of surviving historic and prehistoric rock art is found in caves or partly enclosed rock shelters; this type al ...

and other artefacts. It has been applied to hundreds of the

Vindolanda tablets The Vindolanda tablets are some of the oldest surviving handwritten documents in Britain (antedated by the Bloomberg tablets from Roman London). They are a rich source of information about life on the northern frontier of Roman Britain. Writ ...

by the Centre for the Study of Ancient Documents at the

University of Oxford The University of Oxford is a collegiate university, collegiate research university in Oxford, England. There is evidence of teaching as early as 1096, making it the oldest university in the English-speaking world and the List of oldest un ...

in conjunction with the

British Museum The British Museum is a Museum, public museum dedicated to human history, art and culture located in the Bloomsbury area of London. Its permanent collection of eight million works is the largest in the world. It documents the story of human cu ...

. It has also been deployed, by Ben Altshuler of the Institute for Digital Archaeology, to scan the Philae obelisk at Kingston Lacy and the

Parian Chronicle The Parian Chronicle or Parian Marble (, Mar. Par.) is a Greek chronology, covering the years from 1582 BC to 299 BC, inscribed on a stele. Found on the island of Paros in two sections, and sold in Smyrna in the early 17th century to an ...

at the

Ashmolean Museum The Ashmolean Museum of Art and Archaeology () on Beaumont Street in Oxford, England, is Britain's first public museum. Its first building was erected in 1678–1683 to house the cabinet of curiosities that Elias Ashmole gave to the University ...

; in both cases scans revealed significant, previously illegible text. Method was also used for identifying microscopic worked antler from

Star Carr Star Carr is a Mesolithic archaeological site in North Yorkshire, England. It is around five miles () south of Scarborough. It is generally regarded as the most important and informative Mesolithic site in Great Britain. It is as important to ...

and recording ancient rock art in

Armenia Armenia, officially the Republic of Armenia, is a landlocked country in the Armenian Highlands of West Asia. It is a part of the Caucasus region and is bordered by Turkey to the west, Georgia (country), Georgia to the north and Azerbaijan to ...

. A 'dome' supporting twenty-four lights has been used to image paintings in the

National Gallery The National Gallery is an art museum in Trafalgar Square in the City of Westminster, in Central London, England. Founded in 1824, it houses a collection of more than 2,300 paintings dating from the mid-13th century to 1900. The current di ...

and produce polynomial texture maps, providing information on condition phenomena for conservation purposes. Studies of the technique at the

and

Tate Tate is an institution that houses, in a network of four art galleries, the United Kingdom's national collection of British art, and international modern and contemporary art. It is not a government institution, but its main sponsor is the UK ...

concluded that it is an effective tool for documenting changes in the condition of paintings, more easily repeatable than raking light photography, and therefore could be used to assess paintings during structural treatment and before and after loan. Twelve dome-based systems built by the University of Southampton have been used to capture thousands of cuneiform tablets at various museums. The technique is now also finding uses in the field of

forensic science Forensic science combines principles of law and science to investigate criminal activity. Through crime scene investigations and laboratory analysis, forensic scientists are able to link suspects to evidence. An example is determining the time and ...

, for example in imaging footprints, tyre marks, and indented writing.

References

{{Reflist

External links

Polynomial texture mapping
(

Hewlett Packard The Hewlett-Packard Company, commonly shortened to Hewlett-Packard ( ) or HP, was an American multinational information technology company. It was founded by Bill Hewlett and David Packard in 1939 in a one-car garage in Palo Alto, Californi ...

)
Project applying polynomial texture mapping to an ancient sculpture
(

University of Southampton The University of Southampton (abbreviated as ''Soton'' in post-nominal letters) is a public university, public research university in Southampton, England. Southampton is a founding member of the Russell Group of research-intensive universit ...

- Archaeological Computing Research Group)
Reflectance Transformation Imaging (RTI)
(RTI overview on the Cultural Heritage Imaging website)
Sixteen interactive renderings
of Polynomial Texture Mapping (or RTI) of 8th-century illuminated manuscript, revealing difficult to see dry-point writing (

University of Oklahoma The University of Oklahoma (OU) is a Public university, public research university in Norman, Oklahoma, United States. Founded in 1890, it had existed in Oklahoma Territory near Indian Territory for 17 years before the two territories became the ...

)
Heritage Visualisation website
with Pixel+ viewer and an integration solution for Single Camera Multi Light datasets 3D imaging Conservation and restoration of cultural heritage Digital imaging Image processing Texture mapping Virtual reality

Origins

Methodology

Applications

See also

References

External links