DIGITAL REPRESENTATIONS
OF
HISTORIC BUILDINGS:
The Tron Kirk
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University of Edinburgh-Department of Architecture| MSc Design & Digital Media| Tina Mikrou | September 2001
D
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R EPRESENTATIONS
[ THE
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CASE
OF
BUILDINGS :
HISTORIC
T OOLS
L
M ETHODS
STUDY
KIRK
by
Tina
Student
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IN
OF
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EDINBURGH ]
Mikrou the
degree
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MSc in Design & Digital Media University 2
of 0
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1
T ABLE
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[A C ASE S TUDY ]
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ACKNOWLEDGMENTS
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1
INTRODUCTION
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BACKGROUND REPRESENTING IN REPRESENTING IN
2
THE PAST THE PRESENT
37 39
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T HE COMPUTERIZED MODEL TOOLS & METHODS IMAGE BASED MODELLING & RENDERING
14 15 16
BUILDING
19 19 21 23 23 24 27 29 29 30 31
THE
MODEL OF
THE
TRON KIRK
SOME HISTORY MOTIVATION SOURCES SOFTWARE CONSTRUCTING THE MODEL SIMULATION OF THE CONSTRUCTION PROCESS SIMULATION OF THE NATURAL LAWS CREATING THE CONTEXT OF THE BUILDING POSSIBILITIES & RESTRICTIONS EXPLOITING THE COMPUTER MODEL
35
10 10 11
CONCLUSIONS
REFERENCES
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F OOTNOTES 6 39
University of Edinburgh-Department of Architecture | MSc Design & Digital Media | Tina Mikrou | September 2001
A CKNOWLEDGMENTS This Project would not have been possible without the generous help by Simpson & Brown Architects, who provided general and detailed drawings of the Tron. I would like to thank them as well as Page & Park Architects who provided the original plans of Hunter Square and John Mengham who provided parts of Edinburgh’s Old Town Model in Digital form. Special thanks also to John Hope Architect, my employer while in Edinburgh, for introducing me to Stuart Brown & David Park, for his help including comments and equipment and for giving me the chance to work at his office. Many thanks also to Peter and Lale, my flatmates, who patiently watched, commented and encouraged my effort. Last but not least is to be mentioned the financial support of the Foundation of Panagiotis & Efi Mihelis that provided one year scholarship for the purposes of this Postgraduate Course in Design & Digital Media at the University of Edinburgh.
University of Edinburgh-Department of Architecture | MSc Design & Digital Media | Tina Mikrou | September 2001
4
1 I NTRODUCTION The object of this dissertation is one among the many of the buildings that constitute the heritage of the city of Edinburgh: the Tron Kirk. A landmark of the Royal Mile, situated in the middle of High Street, halfway between the Castle and the Palace of Holyrood, it stands out with its impressive steeple and its elegant clock, lighted during night time. Built some three hundred years ago to host the congregation of St. Giles when the latter was transformed into a cathedral it has been associated with important moments of the life of the city. Although relatively simple in structure and rather severe at first glance, it incorporates several significant morphological elements, typical of both gothic and neoclassical orders. The building of today is the result of several alterations: Originally T-shaped, the south and north elevations were shortened and the south aisle demolished for the formation of the South Bridge and Hunter Square respectively. The original wooden steeple of Dutch derivation was also completely destroyed by fire and subsequently replaced by the present much more elaborate and dramatic one. 1
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Nowadays the Tron Kirk reveals more an atmosphere of decay rather than the glorious days of the past. Despite the fact that the building is currently being used for temporary exhibitions and as a seasonal visitor information centre it looks rather neglected and as if it lacks of a proper use. The objective of this project is first to present an overview of the Computer Aided Design and Image based tools & techniques that are widely being implemented today for the analysis and conservation of buildings and in relation to the study of their history and architecture. Then, to describe the way that some of them were used for the study and the analysis of the Tron Kirk. A detailed 3D computer model of the existing building and two more of its former phases will be the final product which will be expected to serve various purposes: -To allow a thorough understanding of the structure of the building. -To trace and list remarkable ornaments and details, reconstruct the original wooden roof and generate digital representations of the earlier phases and the interior decoration. -To provide the material that in a next stage could be used for the production of a multimedia interactive presentation of the history and architecture of the Tron. This could take the form of either a CD-ROM or an installation inside the building itself, combining interactive projections2 and (or) touch screens. In the case that Augmented Reality Equipment would be available then visitors could also enjoy walking around the real building and get instant-interactive information and perception of its previous phases. -To provide a simulation environment where both interior and exterior future interventions could be first tested before actually implemented. For instance, whatever use might be chosen for the building or any installation or exhibition, could be explored in terms of aesthetics and functionality on the 3D model that will provide all necessary perspective views and renderings and will allow real time visualizations. The same applies for lighting simulations using particular light sources and light distribution techniques, in the case that decisions to illuminate the building were to be taken.
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2 B ACKGROUND R e p r e s e n t i n g
i n
t h e
p a s t
Representations of buildings and their environment can be traced back in time as far as in the 5th century BC when scenography3 was introduced in the ancient Greek theatre for the “action� to take place in a space that recalls the real world. Representation constitutes a mean that architects have always used in the form of different media and in order to communicate their ideas so that also others can visualize what they have in mind. Representations of historic buildings in particular and their components have existed from the age of Vitruvius when they were for the first time systematically recorded and classified so that they could be studied and probably totally or partly reproduced. Students of Architecture -especially in traditional schools such as the Beaux Arts- are expected and taught to represent existing significant buildings both with drawings and physical models in order to investigate and comprehend them. Artists as well have always contributed to the representation of
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buildings in their own way and in the form of watercolours, lithographies and engravings. R e p r e s e n t i n g
i n
t h e
p r e s e n t
Information technology provides new tools for the representation of historic buildings and the reconstruction of destroyed or unbuilt projects. Computer modelling constitutes a rather fascinating process: Architects can draw and at the same time experience the feeling of construction and shaping in a three dimensional space. Particularly complex objects and structures -such as gothic ones or domes for instance- that would be difficult to manually build in a physical model, can be visualized and understood through a 3D computer model. Buildings that no longer exist or are in great risk to disappear, or others that were never built but only designed or described by famous architects, can be now virtually built and even experienced through walkthroughs or other more sophisticated immersion systems. A 3D computer model of a historic building constitutes a digital database in which all the information about it [structure, materials, ornamentation, history & different phases of its life] can be stored and then studied or discussed. Through the World Wide Web such a database can be easily distributed and retrieved all around the globe. Both because they are the outcome of a fascinating process but also because they serve multiple tasks, computer models of several buildings are being produced in academic institutions and private practices. Some of them worth mentioning are the following: The dome of the church of Hagia Sophia in Instanbul, considered to be the greatest achievement of the Byzantine architecture, and well known for its enormous dimensions and its revolutionary structure was modelled by Takehiko Nagakura and his team at Harvard University. For that purpose they developed a prototype software that models domes and vaults of various dimensions and shapes and which allowed them University of Edinburgh-Department of Architecture | MSc Design & Digital Media | Tina Mikrou | September 2001
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to arrive to significant conclusions regarding the geometric principles of the shape of the dome. For the same project they also designed a projection device for interactive display of information in relation to the action of the viewer.4
The Amiens Cathedral Project was carried out by the Digital Design Lab at Columbia University. The impressive Gothic structure was modelled using Soft Image and several still images, animations and a video were produced. The material was gathered in a web site hosted by the Media Centre for Art History, Archaeology and Preservation, an institution that explores the creative application of technology in research and student learning.5 The city of Miletus and the Temple of Zeus in Ancient Olympia were modelled by The Foundation of the Hellenic World using Softimage as well. Part of the material produced is used for display in virtual reality systems -ImmersaDesk and ReaCTOR- that allow visitors to fly through the cities and see them as they existed in antiquity. Another part, in the form of photorealistic images, animations and Reconstructions through the use of VRML, are used for CD-Roms and the Internet.6
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Significant unbuilt projects of the early Modernism, such as Le Corbusier’s “Palace of the Soviets” and Tatlin’s Monument to the Third International have been computer generated by The Team Unbuilt at the MIT allowing for the first time perceptions of Modern Architecture masterpieces.7 The representation and analysis of Architecture designed and built by someone else, through the creation of a computer model serves as well educational purposes. Therefore it has been introduced in the training program of several schools of Architecture that use digital systems without disregarding other graphic media, to enhance the experience of conceiving and representing. In an effort to integrate digital modelling as an active learning tool, students are encouraged to “analyze and decompose architecture, get to know the specific grammar of a Cad system and build a model of architecture with it.”8
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3 T HE C OMPUTERIZED M ODEL Generally architects hardly ever build buildings; they draw drawings for their clients to approve and for the constructors that will actually build them. Yet they can always taste the pleasure of “building� by making models, physical and now also digital ones. Similarly to a traditional model the computerized model is a 3D construction, it consists of three dimensional elements and it provides numerous points of view. However a few significant differences should be mentioned: Physical models are built under a scale (usually 1:200, 1:100, 1:50, rarely 1:20 or more). Computer models are always constructed in one to one scale therefore the amount of information incorporated in each one of them is considerably different. Virtually a computer model can include every bit of the real building. One of course has always to decide on the amount of detail that he wishes his model to contain -since the size of the file also needs to be taken under consideration.
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T o o l s
&
3. T HE C OMPUTER M ODEL
M e t h o d s
Several cad systems are available today: Sophisticated applications for power workstations but also commercial and affordable packages have equally evolved and notably improved. While most of these systems present significant differences they also have some functionalities and methods in common: The organization in layers -a method that derives from traditional ways of working -being perhaps the first that one could think of. Antonino Saggio (2000) describes this organization as “horizontal hierarchical structure” to differentiate it from the “vertical”, more important one (variously known as symbol, type, object etc)9: Most cad software allows the organization of a project through combinations of sets of elements and through dynamic relations between data. Flexible design environments are created in this way since we can achieve automatically several modifications to the whole structure by altering one of its components. The concept of parametric design, integrated in any computer model is what renders it an extremely powerful tool. In the case of Restoration Projects in particular, this facility becomes even more important: When working with old buildings, significant parts of them or information regarding their history might be missing, but we still need to know what they would have looked like in the past. Having a computer model based on the data that are known we can create several alternatives that will allow us to compare and evaluate different solutions before we actually decide which one of them might be most likely. Then if new discoveries will be available the computer model can be easily modified and updated. At the same time when we have information about earlier phases of an existing building, they also can be represented with relatively little effort by adding or subtracting information from the initial version of the model. Therefore several reconstructions can be generated that allow us to visualize what the building -or its surroundings- would have been like at different historical phases. A list of the several cad programs will not be catalogued here. However another method generally defined as Image Based Modelling, is worth mentioning because it can be particularly useful in generating 3D models of existing structures from simple photographs. University of Edinburgh-Department of Architecture | MSc Design & Digital Media | Tina Mikrou | September 2001
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I m a g e
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M o d e l l i n g
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3. T HE C OMPUTER M ODEL
R e n d e r i n g
Photography has traditionally been a tool for restoration architects and heritage recorders, supplementary to other tools such as sketches, measured drawings and notes that provide the basis for the documentation and assessment of an existing building. Photogrammetry is a technique that uses photographs for mapmaking and surveying. As the name suggests it is about measuring in images: Suitable pairs of photographs are captured and then “read” stereoscopically through special machines that can also do the drawing. Although it provides the highest degree of accuracy and involves very few on site measurements, as far as surveys of monuments and other existing buildings are concerned, it was never widely applied mostly because of the particularly expensive equipment it requires. Urs Hirsberg & Aandre Streilein (1995) describe DIPAD (Digital System for Photogrammetry and Architectural Design) a system that integrates photogrammetric methods with the capabilities of CAAD. Its main principle is that parts of the building appearing on a photograph are being approximated to geometric topologies. “Then the photogrammetric algorithm matches these topologies with the image data of multiple images and derives its exact three dimensional position and geometry”. The 3D model is generated in a CAAD environment and texture maps -generated from the images used for measurement- can be applied to the faces of the model to make it look more realistic. It is a system in which “the human operator assumes responsibility of the image understanding part, while the actual measurement is automatically handled by the computer”.10 Several packages are available today that allow extractions of 3D models out of 2D photographs with principles similar to the ones described above. Two of them -CANOMA & PHOTOMODELER.PROwere intended to be used for this project in order to be “tested” for their capabilities and efficiency. Limitations of time and some observations made at an early stage didn’t allow a thorough exploration and critical evaluation. However a few comments could be made: With CANOMA version 1.0 one can import photographs and then select out of the 3D shapes
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available for modelling from the software (called objects or primitives such as cubes, pyramids etc) to “pin” them to the corners of parts of the building -or any object- in the photograph. The composition of these shapes results to a 3D model of a building or a group of buildings. One can then rotate the 3D creation or walk through it, texture maps can be applied and several formats can be exported (dxf, wrl).11 CANOMA is scaleless and does not allow any measurements, it also lacks some important shapes such as spheres for instance. The 3D models created in this way are rather simplified ones that can look a bit more realistic by the application of the texture maps. Yet in this case, the result is satisfactory enough only when the camera is quite away from the models being shown. However the simplified model is not necessarily something undesirable and at times can be even useful. While a model of the Tron created with CANOMA could not be as detailed nor as accurate as the one created with a CAAD program, the modelling of its surrounding buildings [in order to form the context of the Tron], that would require not much detail nor accuracy, could be generated faster and be more suitable in order to create VRML files. [In reality that was the initial idea for CANOMA to be used for but was not actually implemented because suitable photographs –aerial ones from a short distance that would allow both the roofs of the buildings and the roads to appear together- were not available. When working with CANOMA, one has to define a ground plane that represents the level on the top of which the object to be model stands. At the same time, the more of the sides of the object appearing in a single photograph the easier it is to extract a 3D model out of it. Therefore, although not a prerequisite, such photographs would have been much more helpful.]. PHOTOMODELER PRO on the other hand is a more sophisticated program that seems to meet the standards for accuracy and detail that the survey and documentation of a monument or any existing building would require. One has to import overlapping photographs taken from different angles. After that he has to mark reference features using points, lines and edge tools and give instructions to the software to match up points across the photos. Then the program “processes” and adjusts the input data and creates “3D point data to produce an accurate 3D model”. The model can be viewed, rotated and exported to other CAD, Animation or Rendering software. [The version available was a trial one that would not allow any savings so was not actually implemented but only “superficially” explored].12 University of Edinburgh-Department of Architecture | MSc Design & Digital Media | Tina Mikrou | September 2001
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Definitely these techniques are very useful tools, yet an observation should be made: Generally speaking one gets coherently the idea of the structure of the building that he models when using a CAD software. However when he uses one of the Image Based Techniques he can only model what is visible therefore the structure becomes less important and could even remain unknown. Urs Hirsberg & Aandre Streilein (1995) describe this as a “superficial” approach regarding the way that architects are expected to work. Nevertheless they argue that it is possible to describe buildings by their surfaces and to “derive much information about the construction of objects from their appearance”13 It remains to be agreed whether this is actually possible or not. In any case, if we want to make a computer model of a building for educational purposes, because we want to study and get to know its structure and form, the above techniques are not the appropriate ones to use.
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4 B UILDING S o m e
THE
M ODEL
OF THE
T RON K IRK
h i s t o r y
The Tron Kirk was one of the four early parish churches built in Edinburgh after the Scottish Reformation (1560-1561). Designed by John Mylne, the King’s Master Mason, a famous architect of his time and decorated by his brother Alexander Mylne, a famous sculptor of his time, up to date in style and plan, with similarities to churches in the Netherlands and Denmark was meant to be an important edifice. Built between 1637 and 1641 and for the first time used as place of worship in 1647, it was not completed until sixteen years later.14 The shape is rather simple: Rectangular with two gable walls forming the western and eastern elevation and a tower projecting out of the body of the church in the middle of
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the northern elevation. Originally it consisted of five bays and a south aisle but around 1785-1789 major reconstruction works took place to allow the formation of South Bridge and Hunter Square. The building was then shortened symmetrically, the bays were reduced from five to three, two of the four facing windows together with the south aisle were removed. The northern Elevation is the most interesting one with two round-arched windows supporting triangular pediments, a round-arched and corniced renaissance doorway and the projecting tower over the door. Round-arched, with tracery of a late gothic pattern and supporting pediments are also the windows in the remaining elevations. The current steeple was built in 1828 and is much larger and more formal than the one it replaced. The old steeple was built after the model of the then existing one in Holyrood Chapel. Of Dutch derivation following a design applied on several public buildings throughout Scotland at that period, was made out of wood and iron and covered by copper. It was destroyed in 1824 by a fire –known as the “great conflagration”.15 Particularly interesting is the hammer-beam oak roof of unusual latticed truss construction enriched with gilt “knops”. It survived from the fire of 1824 and was of the same design and probably by the same craftsmen as that in the Hall of the Parliament House.16 In addition to the roof, two giant Roman Doric columns and two half columns supporting semicircular arches dominate the -otherwise empty- interior today. In the past there used to be a pulpit at the north and a gallery around the remaining three sides supported by elegant ionic wooden columns. Access to the gallery was by a turnpike stair at the base of the tower. Impressive stained glass windows were a later addition and contribute to the mystical atmosphere that the space reveals nowadays. University of Edinburgh-Department of Architecture | MSc Design & Digital Media | Tina Mikrou | September 2001
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The Tron has been a fashionable place of worship. At the same time it has been allied to several historical events: it was there that the General Assembly met during the years known as the “Ten Years Conflict” (1829-1840) and that Alexander Duff, the first Scottish missionary to India, detailed his experiences to the East..17 Nevertheless by 1952 it was closed as a place of worship and was not reopened until 1987. Since then it has been used for “ variety of temporary purposes until its long term future is decided”. 18 M o t i v a t i o n Although it could not be described as beautiful, the Tron Kirk is impressive and no doubt distinct. A relatively simple structure that lacks in ornamentation if compared with other significant buildings in Edinburgh but at the same time with enough exciting elements rendering it “cheerful” and allowing plays of light and shadow. Outstanding in its context, its surroundings and Hunter Square in particular contribute to its prominence. A fugitive idea to make a computer model of the Tron passed by my mind long before the subject of our dissertation was to be decided19. A few months afterwards, during a discussion with Roy Middleton from EDVEC, he suggested that the Tron was actually one of the buildings with enough history to talk about using a multimedia interactive presentation and -quite important- enough material about this history available.
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VERTICAL C UTTING P LANES
OF
THE
Edinburgh
WOODEN R OOF
4. B UILDING
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(I MAGES R ENDERED
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IN
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F ORM -Z)
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S o u r c e s Being one of the old city churches of Edinburgh much information about it can be found at the National Monument Record: Drawings, old and new photographs, watercolours, newspaper cutouts and a long list of references that allow a thorough documentation. Particularly useful have been the photographs showing the interior galleries, the pulpit and the seats, the engravings showing the building before the formation of South Bridge and Hunter Square and the detailed drawings of the moulding profiles. The general drawings –plans, sections and elevations- used to generate the computer model were provided by Simpson & Brown Architects who did the last restoration project of the Tron in 1974. The context of the building –surrounding buildings and streets- was provided in digital form by the Edinburgh Heritage Trust who have developed a 3d computer model of the whole old town of Edinburgh. Hunter Square in particular was modelled after the drawings provided by Page & Park Architects who designed the current version of it in 1993. S o f t w a r e All modelling was done in Archicad version 6.5 and Archiforma. Rendering was done in Archicad, Artlantis version 3.5, Form-Z RenderZone and 3D StudioMax version 2.5. Canoma version 1 was used at an early stage to explore its efficiency to generate a simplified computer model of the surrounding buildings. Walkthroughs and QuickTime movies were created in Archicad and Artlantis. VRML files were exported by Form-Z and 3D StudioMax. Flash version 5.0 was used to create animations out of still images produced by one of the above software and put together into different frames. Finally Director version 7.0 was used to gather all the material into a multimedia presentation of the several tools used for the model of the Tron. One of the aims of this project was to investigate how several commercial packages that are generally widespread and available can be used together to enhance the creation of a 3D computer model. To find out in what points one is more efficient and more suitable than the other and whether it is possible or not to make them talk to one another. This has been a very interesting process but at times
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rather a frustrating one: All packages export file formats that can be imported by other packages –dxf, obj, 3ds for instance- but this does not always mean that these common platform files can actually be read successfully as expected. At all times “experiments” need to be done to test which platform is more suitable to import or export and in each case which export-import options are better to select. C o n s t r u c t i n g
t h e
M o d e l
In order to give some guidelines on the sort of characteristics CAAD representations should exhibit and the kind of information they should contain in order to facilitate design, Scot Johnson (1995) examines how the human mind works and how it uses representations. He argues that architects in particular, through the years of practice and training, develop skills associated with graphical representations. They remember and think in terms of walls, doors, rooms, entities that “embody structural functions, symbolic meaning and often manufacturing products”. To allow more efficient and productive work, he suggests that any cad software should be developed in the direction to suit
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these skills instead of forcing the user to develop new skills and perform translations. Therefore he proposes that cad representations should: -“let the user do much work in a graphical format” –meaning to avoid writing script that involves numerical interpretations of form and space. -“correspond to architectural elements” -“have characteristics appropriate for each element they represent”.20 Incorporating these suggestions Archicad provides a particularly user friendly interface. Compared to other commercial CAAD packages it has two significant differences: First its tools correspond to architectural elements and second its 3D environment allows sections, elevations and perspective views to be generated at any time during the building of the model process. Unlike other software that use mathematic entities and terms such as points, lines and polylines to describe parts of a building, archicad’s tools are walls, slabs, openings and roofs placed into and forming different stories. All of them are being described by three coordinates, each slab has a thickness, each wall has a height and openings consist inseparable parts of walls: they can only be placed on them and they will move or will be eliminated if the wall is moved or eliminated. Both the 3D environment and the architectural vocabulary constitute two strong points of the software. As most CAD packages it has a “library”21 that consists of several “objects” such as doors windows, furniture and other 3D “primitive” and structural elements. Although this library is relatively rich, there are always bits that one would need in order to construct a model that are not available. Then the user can create and save his own library parts out of the combination of existing ones or “building” completely new ones. [However one
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M ODEL
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important difference exists between the objects provided by archicad’s library and the ones created by the user: The former, all created in GDL [Geometric Description Language] are therefore fully parametric; the latter are not –or at least not in the same degree].22
S i m u l a t i o n
o f
t h e
C o n s t r u c t i o n
P r o c e s s
Constructing a computer model with Archicad is a simulation of the construction process. In the case of the Tron, slabs, walls and roofs were used to build the main body of the church and round arched openings available from the library were placed on the walls. All the architectural elements that needed to be included in the model and were not available from the library were actually constructed as well: Gothic traceries, the several parts of the hammer-beam roof, the pilasters, the elaborate clock and other ornaments were generated out of slabs, meshes, and vertical extrusions and then saved as objects. The moulded profiles were generated with archiforma a rather powerful “add-on” with resemblances to formZ – a section of the profile is drawn and then a path along which to horizontally extrude or a point around which to revolve. This process is also a simulation of the real construction process and therefore allows an in-depth knowledge of the building: In the same way that a mason would form the gothic windows out of curved stones and glass, the modeller can combine meshes with slabs of different depths and materials to reconstruct the stones and the glass.
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M ODEL
The joiner would trace the outline of the several parts of the hammer beam on a piece of wood and then cut them and join them together. The computer modeler will draw the same 2D outline on the computer screen and then will vertically extract the 3D element. All the components of the wooden structure will be modelled separately and then put together properly to form the complete structure. Subsequently the architect-modeller of the gothic windows and the hammer beam roof will get to know their structure better than the architect-drafter. The drafter would need to draw several sections, elevations and plans in order to achieve the same degree of understanding and in order to describe and let other people visualize the complex structure. S i m u l a t i o n
o f
t h e
n a t u r a l
l a w s
The 3D environment that ArchiCad provides consists of three windows: The Plan, The SectionElevation and the 3D window. One can draw a wall on the plan window and once this wall has a height it will appear on the other two. These 3 different windows provide a tool of control: Although gravity does not apply and nothing risks collapse, there are laws to be respected and components have to be placed properly –walls should be well attached to slabs, windows should not exceed the height of the wall etc- or else gaps will appear, or lines will be missing [and while this might not be evident in one projection –ie on the plan- it will definitely be in the other-elevation or 3d]. Tools of control are particularly useful when drawing in 3D space. While the one just described is relatively poor, other programs emphasize on the concept of the laws of nature that need to be considered and indeed provide more powerful such tools. [Sculptor for instance “a computer tool for virtual design in architecture” developed at the ETH Zurich supports, among others, “modelling gravity” and an object falls down if not supported by another object or the ground].23 C r e a t i n g
t h e
C o n t e x t
o f
t h e
B u i l d i n g
The environment of the building forms an integral part of it. It reveals or hides its values and qualities, it allows comparisons of heights, volumes and shapes, it creates shadows or reflects it.
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4. B UILDING
THE
M ODEL
Therefore it is important for the building to be represented in its context –composed out of more or less simplified models of buildings that surround it. Recently it has become a trend for local authorities or organizations to construct computer models of whole cities. The old Town of Edinburgh has been modelled by the Edinburgh World Heritage Trust, therefore the context of the Tron was relatively easy to generate. 3D models of the buildings were provided but Archicad only imports 2D information, therefore they were rebuilt as 3D models based on 2D plans and elevations.
P o s s i b i l i t i e s
&
R e s t r i c t i o n s
Although CAAD has entered most architectural practices many architects involved in Restoration still draw manually and oppose digital representations. They consider the computer to be inadequate to reproduce ornaments and irregularities. As already mentioned CAD software has significantly evolved and provides easy to use tools that in combination with the modeller’s expertises render it possible for virtually any element, tracery and ornamentation to be constructed and incorporated in the computer model. [Naturally at times the task can be significantly labour-intensive therefore considered not to be worthwhile].
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Repr esentations of Historic Buildings : T h e T r o n K i r k o f
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4. B UILDING
THE
M ODEL
However it is true that most CAD programs lack the concept of irregularity so that ‘unorthodox” shapes cannot be easily constructed. Archicad for instance provides only vertical walls that are of the same thickness all the way along24 and only horizontal slabs. Since virtually all vernacular or heritage buildings “suffer” from some kind of deformation -result of their exposition to time, or deliberately assigned to them by their creators- it is clear that inability to represent them reveals the limits of most CAD programs. Often it is possible for these deformations and irregularities to be represented with archicad -with little or more effort depending on their complexity. [For instance a roof25 can be used to represent a leaning slab or a leaning wall. But to use the term “roof” when one means “wall” sounds bizarre, does not suit and “damages” the elegance of the system]. Therefore more flexible tools (walls, slabs, etc) should be adapted by CAAD programs to facilitate the representation of historic buildings in particular. Yet it is not always necessary to build a complicated “irregular” computer model. In the case of the Tron several deformations and deviations from rules of symmetry and orthogonal shapes were not taken into consideration. The computer model produced -although it contains a large amount of details- constitutes a simplified or rather an idealised representation of the reality. [If the model was to be used for the analysis of the pathology and the proposal of consolidation works, such information however should have been included]. E x p l o i t i n g
t h e
C o m p u t e r
M o d e l
It has been argued so far that creating a computerized model of a historic building lets the architectmodeller familiarize with it and get a good knowledge of its form, and structure. Once the model is complete the information stored in this digital database can be communicated to the public. With technology that is widely available today a benefit from the full potential of the model can easily achieved. One can examine it from diverse points of view inside or outside, can create walk or flythroughs and produce simulations of materials and lighting effects. A sequence of pictures of the model projected
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4. B UILDING
THE
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M ODEL
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at a fast enough rate -so that a smooth movement is created- can be used to generate animations of the composition of the building and its components. For the model of the Tron, horizontal or vertical cutting planes saved as still images and put together in flash 5.0 were used to explain the structure of the roof and the gothic windows. Vrml [Virtual Reality Modelling Language] models are also useful since they allow real time navigation and interaction and can be distributed through the Web so that also remote users can access and investigate them. Apparently the amount of detail that models intended to be used for this purpose can incorporate is rather small. Still they can be quite interesting as they offer a good understanding of spatial relations via real time movement.26 In the case of the Tron the creation of VRML files proved to be time consuming and the final result was not satisfactory enough. ArchiCad exports WRL files that are rather “weak� since they lack significant functionalities such as gravity and collision detection. [Contrary to what one would have expected from an architectural CAD program that emphasizes on terms like walls and slabs, the components of the VRML model created by archicad don’t behave as they should and the whole environment resembles more to an object that flies in the air rather than to real space]. FormZ on the other hand generates much more efficient VRML models. The Tron as well as its surrounding buildings modelled in Archicad where therefore exported in FormZ. For this exchange several formats where tested, DXF, OBJ and 3DS where all exported and imported relatively easy and among them 3DS seemed to be the most suitable one -since the original models would retain the different colours assigned to different materials. Still the VRML file exported by FormZ was relatively large so that interaction and navigation within it was not as smooth as it was hoped to be. However Archicad creates navigable -the so called VR- objects. The user defines a spherical path for the camera along which the viewpoint can optionally be positioned and navigated and several images are produced that are automatically converted and saved as MOV files that can be viewed with Quick Time Player. The VR objects can be quite interesting and useful, they allow user interaction and limited navigation within a certain radius.
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Repr esentations of Historic Buildings : T h e T r o n K i r k o f
Edinburgh
4. B UILDING
THE
M ODEL
Material and Lighting simulations can be achieved through various Rendering Engines available by ArchiCad, Artlantis and FormZ. In the case of the Tron a few images were generated applying different textures but generally photorealistic representations with texture maps were avoided. The reason is that while photorealistic representations of new buildings can be convincing and useful, the same does not apply to old buildings that bear the signs of the past and their materials have unequally been affected by the weather conditions and other factors. Photorealistic representations should reproduce this aging of the materials and the deterioration of the structure –which might be possible but would require much effort and time. The goal should be to represent the reality rather than replace it. Simple materials do not distract the audience and enhance the understanding of the values of the building. They reveal its structure and its morphology instead of creating a fake sense of reality. Photorealistic representations might be useful to give an impression of what the building looks or would have looked like in the past but at times this task can be served more efficiently by photographs. While textures applied on new buildings give an impression and allow us to visualize what the building is going to look like they might not be that successful when applied onto old ones. The fourth dimension of architecture –the building in time- is also to be considered.
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5 C ONCLUSIONS With the use of tools that correspond to architectural elements and concepts Archicad simulates the construction process and allows the digital recreation of an edifice from the ground up, step by step. In this way architects - conservators can acquire an in depth knowledge of the structure of their object, analyse, decompose and recompose it. Computer modelling in general makes possible the representation of complex parts of a building and of several of its historical phases so that all of its components, such as its history and its actual state can be integrated and stored in a single database. Once this database has been completed can be manipulated to serve educational purposes and promote the cultural heritage of a place. Multimedia interactive presentations and the creation of a virtual environment [in the form of VRML files for instance] available through the Internet, provide efficient storing, retrieving and sorting of information. Dissemination of knowledge in this form is addressed to and can be easily reached by a broader audience. Therefore it contributes to a better perception and appreciation of historic buildings in a larger scale. However such interactive presentations and virtual environments should emphasize on describing and representing reality rather than replacing it. University of Edinburgh-Department of Architecture | MSc Design & Digital Media | Tina Mikrou | September 2001
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5. C ONCLUSIONS
Regarding the objectives of this dissertation as described in the introduction chapter a fairly good comprehension of the structure of the Tron Kirk was achieved and the representation of significant ornaments, other details as well as the reconstruction of the hammer beam roof was made possible. Limitations of time mainly did not allow the reconstruction of the former wooden interior panelling and decoration. For the same reason, lighting simulations were not thoroughly investigated as hoped at the beginning. However much of the material that could take the shape of an educative cd-rom has been produced and further utilization of it in combination with some more modelling and a suitable sorting and layout of images, animations, text and sound could result in a digital story-telling of the Tron Kirk of Edinburgh.
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FOOTNOTES 1
Forbes Gray, W. Historic Churches of Edinburgh.
2
The idea derives from a similar project developed at the ETH Zurich and described by Patrick Sibenaler, as Visdome in bits and spaces, p157-159 3
The term refers to theatrical paintings representing a Palace or a Temple that served for background and formed the Scene of the Ancient Greek Theater. 4
The device is called Digitarama and is described by Takehico Nagakura, MIT (1997) in “The Virtual Architecture”, p116 5
http://www.mcah.columbia.edu
6
http://www.ime.gr
7
Takehico Nagakura, MIT (1997) in “The Virtual Architecture”, p120
8
Cantos Selles’s, Pasqual and Mas Llorens, Digital Modelling Tools at the Dsign Studio: Methodology, MULTIMEDIA AND ARCHITECTURAL DISCIPLINES, Proceedings of the 13th European Conferenceon Education in Computer Aided Architectural Design in Europe, 1995, p6164 9
Antonino Saggio, “An intelligent Model”, Preface to Virtual Teragn, CAAD in Historical and Critical Research, BIRKHAUSER, 2000, p5-7 10
Urs Hirsberg & Aandre Streilein, CAAD Meets Digital Photogrammetry, ACADIA 95, p299
11
www.metacreations.com
12
www.photomodeler.com
13
Urs Hirsberg & Aandre Streilein, CAAD Meets Digital Photogrammetry, ACADIA 95, p308
14
Gifford John, McWilliam Colin, Walker David, The Buildings of Scotland, Edinburgh, Penguin Books, 1984, p174-175 15
The Royal Commission of the Ancient Monuments of Scotland, An Inventory of the Ancient and Historical Monuments of the City of Edinburgh, 1951, p35 16
Gifford John, McWilliam Colin, Walker David, The Buildings of Scotland, Edinburgh, Penguin Books, 1984, p174-175 17
Historic Churches of Scotland
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18
The city of Edinburgh council, brochure on the Tron Kirk.
19
I became fascinated with 3D computer modelling of historic buildings after working in some restoration projects during the past few years. Ever since it has become a habit somehow: Each time a building captures my attention I start thinking whether I would enjoy to make a digital model of it. 20
Scot Johnson, What’s in a Representation, Why Do We Care, and What Does it Mean? Examining the Evidence from Psycology, ACADIA 97, Representation & Design. P5 21
o tade milaei gia ikonoeque
22
For example if we change the width of one archicad window then only the size of the glass will change unless we specify that we wish the size of the frame to change as well. The same does not apply to the new library parts, once we change the size of the object all its components will be resized respectively. 23
Maia Angeli, David Kurmann, Gerhard Schmitt, A new design Studio: Intelligent Objects And Personal Agents in Virtual Environment, ACADIA 1995, p162 24
Walls with different thickness in each of their ends are also available but are less flexible than the rest, they don’t intersect well and windows can not be placed on them. 25
Roofs can get a gradient from 1 to 89 degrees
26 Christodoulou Vangelis, 2001. 3D Monument Reconstruction and its reception by a varied audience. Imeros. FHW
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6 R EFERENCES
Angeli Maia, David Kurmann, Gerhard Schmitt, A New Design Studio: Intelligent Objects And Personal Agents in Virtual Environment, ACADIA 1995, p162 Cantos Selles’s, Pasqual and Mas Llorens, Digital Modelling Tools at the Dsign Studio: Methodology, MULTIMEDIA AND ARCHITECTURAL DISCIPLINES, Proceedings of the 13th European Conference on Education in Computer Aided Architectural Design in Europe, 1995 Galli Mirko, Muhlhoff Claudia, Virtual Terragni, CAAD in Historical Research, BIRKHAUSER, 2000 Hirsberg Urs & Streilein Aandre, CAAD Meets Digital Photogrammetry, ACADIA95
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Edinburgh
6. R EFERENCES
Ken Sakamura and Hiroyuki Suzuki The Virtual Architecture. Tokyo University Digital Museum, 1997 Saggio Antonino, An Intelligent Model, Preface to Virtual Terragni, CAAD in Historical Research, BIRKHAUSER, 2000 Santana Quintero, Neuckermans Herman, Van Balen Koenrand, Three Dimentional representation of the different phases of onstruction and actual state of conservation of the Castle of Arenberg using CAAD and Virtual Reality applications towards its adequate conservation. Scot Johnson, What’s in a Representation, Why Do We Care, and What Does it Mean? Examining the Evidence from Psycology, ACADIA 97, Representation & Design. Sibenaler Patrick, Visdome, bits and spaces. BIRKHAUSER, 2000 Smith, Chris. Theory and the Art of Communications Design. State of the University Press, 1997. Stenvert Ronald, Constucting The Past: Computer- Assisted Architectural-Historical Research; 1991 Butler D., The Tron Kirk of Edinburgh or Christ’s Kirk at the Tron, Oliphant, Anderson & Ferrier, 1906(?) Forbes Gray, W. Historic Churches of Edinburgh. The Moray Press Edinburgh & London, 1940. Gifford John, McWilliam Colin, Walker David, The Buildings of Scotland: Edinburgh, Penguin Books, 1984 The Royal Commission of the Ancient Monuments of Scotland, An Inventory of the Ancient and Historical Monuments of the City of Edinburgh, 1951 CANOMA, User Guide, ArchiCad 6.5, User Guide
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