Dear Alexander the first part was modified  using the critical comments from the submission and I just finished modifying the sections below to answer the critical comments related to it.  The reviewer wanted to know 1. what system was used  2. why it was so bad - added time lines.  3. It was so bad then maybe CSG should not be used. 4. what is a virtual lumber cut... please explain more of how the model was made.  4. In general is where are we going with this..... His edible model of modeling is far from the synthetic future.....  So I added future work.

4.2 Constructive modeling of historical buildings

 
Considering the authors experience of digital data loss were only the last seven years of  twenty years of work , the authors specified CSG representation as the most likely data structure for modeling historical architecture  that might have any possibility of lasting longer than the existing  historical buildings  for the Aizu History Project.15 All parts of the two historical buildings, the Golden Hall at Enchiji and Sazaedô, featured in this paper were created whenever possible with only CSG based entities. However, because CSG is limited in its range of shape representation and the overall size of the models was extremely large, the thatch roof of the Golden Hall and the double helix ramp inside Sazaedô had to be represented to the dislike of authors by a polygonal mesh.  We use AutoCAD rel 12 software with Advance Modeling Extensions (AME).  AME is the implementation of CSG with the CSG tree history.  Furthermore AutoCAD rel  using AutoLISP allows for direct access to the CSG tree history and the creation of third party programs such as the creation of export programs for CSG data.  We in fact are creating HyperFun modeling module for AutoCAD rel 12 that will export HyperFun modeling that is open source.  We have found many errors in the AutoCAD AME implementation of CSG.  However we only have access to the CSG data tree and not the source code for the CSG module.
 
The original modeling of  Enchiji and Sazaedô began ten years ago on 386 and 486 intel class machines  and in using CSG, the computational requirements of use a mathematical representation with a history dictated that sections of the model be developed in many separate files on as many as four different machines at once working on different sections while waiting for the other machines to complete there computations.  We knew that the exponential computational evolution would continue and in five years we would be able to only use one machine.  There were significant problems in data creation and manipulation of sections of the buildings across separate files on different computers as the coordination was all manually done. When combining the files into one file, it is needless to say that this data overwhelmed even the fastest single system at that time.  We found that within five years it was possible to be able to edit Enchiji and Sazaedô on one machine with out much wait time. Now, the entire model of Sazaedô with a large amount of polygon reduction can be handled easily at one time on current machines in animation and rendering systems in real time.  The efforts the authors experienced using CSG in commercial products on single computer systems with the hope of creating digital archival data at seems wasted. There is some doubt that even this CSG constructed data will live through the next several decades because of the proprietary nature of the commercial software.  We fully expected that AutoCAD Rel 12 to stop working on the new MS operating systems like windows 2000 or XP and we would have to use older system to do the programing necessary to migrate the data into HyperFun, Linux and  new hardware.  However AutoCAD rel 12 was very well done program and  AutoCAD rel 12 AME continues to work on the new systems.  Because of the errors we have found in AME  the quality of  the AME CSG modeling data base is in question.   It will  take more effort to extract the CSG data structure embedded in AME as it would to modle the buildings again, but this is a part of our planned research.  We now have the HyperFun language which we did not have when we first stated and the next step in our research  is to create a "CAD" style third party program HyperFun based repsentation in AutoCAD rel 12 as the frist step in the creation of seperate system Synthic CAD modeling system useing a digital base simulation interface based on HyperFun / F rep.   We need to mention and give credit to the great programers that created AutoCAD and note that if it were not for the many forms of open data access with in the AutoCAD program allowing with the use of AutoLISP the modification of its user interface or the data directly we could not have done the work at all.  The development of translation tables from the four different measurment systems used over time in the documentation we used and the research and development of other 3D modeling tools related to our work has made the work possible.  AutoCAD rel 12 with AME and AutoLSP is in the finial stage of research being used to mockup and create a seperate HyperFun F-rep Synthic CAD modleing and translation tools.  After twenty years of extended use of AutoCAD software even with its stiff draftign paper style interface that makes it very difficult to move the user view point it will be missed when it know longer will run on the new platforms of the future.

The benefits of using three-dimensional graphics techniques in constructing models are obvious. First of all, models can be manipulated to provide multiple viewpoints. Rotating a model can provide a better understanding of the physical relationships of the components of the actual structure, as well as the construction techniques involved. Moreover, three-dimensional models can replicate the actual construction of the building itself, including features normally hidden to the eye, such as interior bracketing, and the model can be deconstructed to reveal such hidden features. Images of our work below on the two Buddhist temple buildings in the Aizu region of Japan illustrates these benefits.
 

Golden Hall at Enichiji

The first structure that we modeled using the AutoCAD AME  CSG system was the Golden Hall at Enichiji, a temple located at the foot of Mt. Bandai. Although Enichiji was the religious center of the region throughout much of the Heian period (794-1185), no buildings or images from that period are extant today. In order to produce a model of the Heian Golden Hall, the structure that housed the temple's most important Buddha-images, the authors relied on data introduced in archaeological site reports.16
 
 

Figure 4: Structural view

The construction of the Golden Hall model was a difficult task. At present the only solid information is the existence of seven foundation stones for pillars, demarking the north and part of the east walls. A base of piled stones also stretches along the north and east walls, and remains of a retaining wall abut the (surmised) southwest corner. This information has led archaeologists at the site to conclude that the building measured five bays from east to west and four or five from north to south. We have constructed the Golden Hall model as a five by four building (Figs. 4 and 5).
 
 

Figure 5: Normal view

In addition to archaeological data, the model was based on standard temple-building practices of the eighth and ninth centuries.17 We also took into consideration the snowy climate of the Aizu region, which dictated a steeper roof slope than is common in other areas of Japan. In addition, we consulted Yamagishi Seiji, a master miya daiku (shrine carpenter) and the scion of an 800-year carpentry tradition in this region.
 

Sazaedô Pagoda

 Recently declared a National Important Cultural Property, Sazaedô, a pagoda built in 1796 in Aizu-Wakamatsu, is noted for its unique architectural feature, a double-helical interior walkway that takes visitors from the front entrance to the top of the structure, then over and down to the back entrance. The double helical walkway is part of an interior tower (Figs. 6a, b and c). (For more details on the Sazaedô construction, including black and white reproductions of these figures and some others, see Vilbrandt, Goodwin, and Goodwin, 1999.18 The drawings in Figs. 6c, 7c, 8c and 9a were adapted from engineering blueprints done in 1965 by Kobayashi Bunji.)
 
 
Figure 6a: Interior tower with image alcoves - wire frame
Figure 6b: Interior tower - colorized
Figure 6c: Full drawing showing 


the location of the interior tower .

 The 3D CAD model can be used to display such components separately, so that the construction may be seen and understood. Even an actual visit to the site does not enable such views.
Figure 7a: Exterior tower with walls added - wire frame
Figure 7b: Model of exterior tower with walls - colorized
Figure 7c: Full drawing showing the location of the exterior tower

The interior tower is housed in an exterior tower, with a separate support structure (Figs. 7a, b and c).
 
Figure 8a: The exterior tower overhang - wire frame
Figure 8b: The exterior tower overhang - colorized view
Figure 8c: Full drawing showing the location of the exterior overhang

The tower exterior shows helical overhangs protecting the windows from direct sunlight (Figs. 8a, b and c).
Figure 9a: Roof - engineering drawing
Figure 9b: Roof - wire frame 3D CAD model
Figure 9c: Roof - false color CAD Model
Figure 9d: Roof - Rendered 3D CAD model, from below

Fig. 9a is an engineering drawing of the roof shown from below. By using measurements from this drawing, and supplementing them with measurements taken on site, a 3D CAD model was constructed, and is displayed in the wire frame view (Fig. 9b) and the rendered views (Figs. 9c and 9d).

The entrance and its canopy are structures which can be better understood from the model (Figs. 10b, 10c, and 10d) than from a photograph (Fig. 10a) or even from a visit to the actual site, since they are complex objects and access and sightlines are restricted.
 
Figure 10a: Entrance canopy photograph Figure 10b: Entrance canopy – wire frame 
CAD model
Figure 10c: Entrance canopy rendered Figure 10d: Entrance canopy – alternate view

It is possible to select only one section from the single CAD model of the entire structure, and display it from multiple viewpoints and with various levels of detail (Figs. 11a, b and c).
Figure 11a: Wire frame of the base Figure 11b: Colorized CAD model of the base Figure 11c: Base – details of the supports

Because of the constructive approach, any part may be rendered without displaying the other components, as shown in (Fig. 11d), and an external shell may be fully rendered (Fig. 11e).

Figure 11d: Rendered model showing helical structure
Figure 11e: Fully rendered view

The models illustrated above are virtual constructions using virtual lumber cutting, positioning and joining according to the specifications of the miya daiku based on emperical knolwage of the past.  By a virtural lumber cutting  positioning and joining we mean that we create each piece of temple from virtual parts that represent the shape of each piece of lumber in the same order, that would have been used by the miya daiku.  The virtural lumber cutting, positionsing and joining empirically shows the value of digital preservation of cultural heritage using constructive modeling. The 3D model has recently been used to produce high quality renderings of the interior of Sazaedô, as would be seen by a person walking through the structure,19 and to produce QuickTime and AVI movies of the journey through the temple. We plan to enhance the current model by including 3D reproductions of the images formerly enshrined in the building. We also intend to develop VR facilities to allow the examination of these images independently, and to allow the viewing of parts of the structure that cannot be accessed in the actual building.  See http://ggpl.org/sasa2001/
 

Virtural Surfaces to Synthetic Objects

 The miya daiku uses specific parts of the tree or piece timber in a specific place or way.  Therefore the timber is saw-milled in a specific manor and the parts of each piece of timber are noted and used together to create a "living" harmonious structure.  A simple example of this specific use of timber is that the main columns of the temple are cut from four sides of the mountain and there orientation to the earth and to each other on the mountain is maintained in the structure if possible.   With the use of HyperFun representation we can reach beyond the virtual surfaces of object pasted with inaccurate bit maps that are a poor representation of the actual object,  in the future with weather records and growth rings of other trees  we can synthetically grow a tree using volume modeling and then  create a synthetic piece of timber and using virtual using the same type of milling procedures and operations create a synthetic parts and build a synthetic representation of the temples mention above.  The results of the application of volume modeling of mixed materials of the different densities of wood we call wood grain would create synthetic trees.  Synthetic simulations of the procedures and processes of the miya daiku would allow us a deeper understanding  the past and would archive not only the historical objects them selfs that hint of the possilbe processes used, but will allow us to back engeer and archive the miya daiku's materials, tools and practaces them selfs.