Preservation and Restoration of Historic Vessels in Virtual Environments
Otto P. Jons
Executive Vice President
Advanced Marine Enterprises, Inc.
A Nichols Research Company
A nation's cultural resources are an integral part of its identity. Therefore, preserving what still exists (or restoring what is already partially lost) is very important.
Preservation and restoration to date have been primarily aimed at (a) physical objects (including building, structures, machines and other artifacts) and (b) original records describing what may or may not any longer exist.
In this paper a third class is introduced which, we believe, is an obvious fall-out of the age we live in, the digital age. We like to share our initial experience with the application of a rapidly maturing technology often referred to as "virtual prototyping" to the field of restoration, i.e. "virtual restoration". Specifically,
"virtual prototyping" involves the development and "operation" of a system/product, which does not yet exist in hardware, entirely in a computer-based/digital environment ("virtual environment", VE)
"virtual restoration" involves the development and "operation" of a system/product, which no longer exists (at least not in a functioning state), entirely in a "virtual environment".
Virtual prototyping is driven by a customer's requirements and expectations. Virtual restoration must be governed by strict adherence to historical records. Both must obey the one aspect left unchanged through the ages: the laws of physics.
A note: cultural resources, as a rule, do not (currently) exist in digital form and/or virtual environments. This largely eliminates the distinction, herein, between historic preservation and restoration; in both instances, the prerequisite information on the object to be preserved/restored must be created in the computer in its entirety in either case.
And a word of caution: the term "virtual" may or may not match the readers perception of the same term when used in connection with "virtual reality". The latter expression is often used in connection with efforts to make entertainment more thrilling. This paper addresses scientific applications only.
Virtual environments were born when advances in electronic digital computer technology converged with advances in visual display technology. This computer-based digital technology has revolutionized the way in which we design and develop complex systems, such as air planes, weapon systems, and ships. Both military and commercial systems have been designed entirely in the computer, that is, largely paperless. They have been thoroughly analyzed, optimized and even operated and "tried out" in computer-based simulations in virtual/synthetic environments. This technology, although still incomprehensible to many, is actually very mature and indispensable in many simulation-based training applications for aircraft pilots and mariners.
The computer revolution has made it increasingly easy to create ever more realistic graphic images and to transmit and display them rapidly. Using texture mapping techniques, products can now be presented ("rendered") in "photo-realistic" fashion. From here, it is only a small step to create sequences of computer-rendered images which are animated to convey the illusion of motion. Using such computer-aided animation (CAA) techniques, highly dynamic and even spectacular scenes have been created which can be very realistic in appearance and closely resemble photographic motion pictures.
While scientists and engineers tend to frown upon emphasis on appearance, we believe it is an important aspect of historic accuracy. It is even more important to captivate the general public.
We believe that these technologies offer great opportunities in the field of historic preservation and restoration as well. They can supplement the ongoing effort to preserve our cultural reserves which still exist. However, they offer new worlds of opportunities to restore not only historic objects and artifacts but, in addition, to recreate historic events. They can be recreated in a way to permit experiencing history.
CURRENT VE TECHNOLOGY APPLICATIONS
Two primary areas where VE technology is applied today are of particular interest to virtual preservation and restoration; they are:
(a) Simulation-Based Design, which includes Virtual Prototyping; and
(b) Simulation-Based Training
Understanding the technological maturity achieved in these two applications will help readers appreciate the great opportunities offered to the preservation and restoration of cultural resources, in general, and historic ships, in particular.
The material world we live in, the real world, imposes certain constraints upon us. As a rule, a product must be built and, therefore, exist in hardware before it can truly be tested or operated. It also requires that the product be fully defined or designed before it can be built.
The ideal solution would offer prototypes unencumbered by the constraints of hardware, that is virtual prototypes (VP). This would enable us to:
1. Design the product, with heavy reliance on visualization not only to see how it looks, but how it functions.
2. "Build" the product without the constraint and cost of hardware, after having already optimized the process of manufacture;
3. "Test" the product to validate performance requirements;
4. "Operate" the product, as it is intended to be used, in a realistic environment with real humans at the controls -- although the product does not yet exist in the real world.
Today, this ideal has become reality. SBD/VP technologies are applied extensively in virtually all major defense and commercial system development programs. Some examples follow:
Boeing used SBD in its 777 program. At the peak of design work, 238 design/build teams (about 8,000 people, with as many as 6,000 engineers) used SBD in this effort. Data from 4,000 worldwide computer terminals were linked to eight IBM mainframe computers to manipulate over 3 trillion bytes of information (20,000 design releases). By developing the plane on-screen, Boeing was able to run full-scale simulations and correct conflicts in the design without ever having to build a mockup.
McDonnell Douglas has a design, manufacturing and producibility simulation project for virtual manufacturing and virtual prototyping. It focuses on geometry processes for rapidly generating mold-line surfaces for use in various analyses; rapid loads that can be generated early and quickly updated; finite-element modeling for pushing the analysis early in the design process; feature-based design for efficient generation and updating of drawings; and virtual prototyping for automatic generation of electronic mock-ups from design drawings. The latter determines producibility and ensures early on that system requirements will be satisfied.
Lockheed Martin is integrating advanced simulation and modeling tools to create a virtual design and manufacturing environment for the Joint Strike Fighter and the F-22. The Simulation Assessment Validation Environment (SAVE) program integrates a core suite of off-the-shelf modeling and simulation and rapid prototyping tools.
Closer to home, Advanced Marine Enterprises, Inc. has pioneered the application of SBD/VP technologies to several on-going naval ship development and acquisition programs. For example, SBD/VP technologies were used to validate loading and unloading capabilities of Sealift ships, very large vessels carrying tanks, trucks, tractor-trailers; helicopters, in short: everything a modern army needs - entirely in virtual environments; see Figure 1. The LPD 17, a modern amphibious assault ship, soon to be built, is another example of a ship developed entirely in the computer; see Figure 2, showing first the ship by itself and then in its operational environments.
It is safe to predict that virtually all future ship designs will first be fully defined and thoroughly checked out in virtual environments.
Training of aircraft pilots in flight simulators was one of the driving forces behind the emergence of VE technology and has continued to drive its development.
Virtual environments are also used extensively in training ship operators. A host of general and specialized simulators have been developed ranging from full mission bridge simulators to bridge wing simulators. A typical example is shown in Figure 3. It shows a new Ship Handling Training Complex which started operation at the San Diego Naval Station in 1994. The system has a motion base and displays state-of-the-art textured visuals in 225 degrees. Advanced Marine was instrumental in its development.
This capability permits a visual scene display of up to twenty-five detailed traffic vessels at one time, plus a full complement of navigation lights and true perspectives with changes in the vessels' aspects. The visual system exercise area can extend for two-hundred by two-hundred nautical miles. The sky has clouds and full atmospheric affects including horizon glow, haze, and fog. The water surface is simulated with realistic three-dimensional waves and texture. Simultaneous display of approximately one-hundred structures, one-hundred aids to navigation, two-hundred lights, and ten piers is performed at high-level detail on the closest objects by the use of photographic and generic texture.
This application is of special interest to us because the virtual operational environment is a marine environment and the virtual system is a ship (handling) system. Bridge simulators have become so realistic and effective that the U.S. Coast Guard approves their training time for seatime equivalency.
VE TECHNOLOGY APPLIED TO HISTORIC
PRESERVATION AND RESTORATION OF CHURCHES
Advanced computer technology is not unfamiliar to most historic preservationists. Certainly 2D and, to a lesser extent, 3D Computer-Aided Design (CAD) tools have been used to develop historic preservation documentation and, relatively recently, photo-realistic renderings. Typically, however, these tools have been used to document or display static objects, although increasingly interactive visualization is used which permits viewers to change their position in the scene, permitting virtual "walk-throughs."
One such example of preservation in virtual environments involves one of the most historic churches in Rome. Using head-mounted displays, it is now possible to "enter" St. Peter's Basilica anywhere in the world, see Figure 4, because it is preserved in digital form in all its grandiose beauty in a very detailed three-dimensional database which contains the finest details as scanned images. Interactive visualization permits ad-hoc tours, rather than mere viewing of pre-recorded film images.
Another example of restoration in virtual environments involves a Baroque church in the German city of Dresden which still largely lies in rubble, destroyed in World War II. However, as workers lay the first stones to rebuild the "Frauen Kirche" (Church of Our Lady), IBM Germany hired U.S. computer scientists to re-create the church in virtual environments in an effort to raise money to fund the physical restoration.
In Figure 5, the darker stones (bottom left) depict the portion of the cathedral left standing, whereas the inset shows the original before it was largely destroyed.
Using a computer screen or a headset as a window to the virtual world, viewers can see the blue doors of the Protestant church open to a view of an ornate ivory and gold altar and the organ that Johann Sebastian Bach played in 1736.
Light shining through the clear windows illuminates paintings of the Apostles in the inner dome, which computer tourists can observe more closely by pushing a button that enables them to "fly" up there.
THE USS MONITOR PARTIALLY RESTORED
Advanced Marine initially ventured into the world of virtual restoration of historic ships as the result of playful exploration of its young engineers modeling the venerable iron-clad USS Monitor. This then led to the carefully developed digital model, based on historic drawings and data provided by the Monitor National Marine Sanctuary, and a research grant from the National Center for Preservation Technology and Training (NCPTT) to the National Preservation Institute under which Advanced Marine is currently participating. The objective is to demonstrate the application of advanced modeling, simulation, and visualization technology for enhanced cultural resources documentation, with emphasis on maritime and historic properties with dynamic motion. This study has focused on the dynamic motion of the complex turret rotation system and its associated machinery. Also addressed is the dynamic motion of the ship in a seaway. Figure 6 shows resulting graphic representations of the digital database.
A working (virtual) model of the turret and its associated machinery was developed again using reproductions of original drawings and other historic material to ensure engineering and historic accuracy. This model was used to demonstrate the dynamics associated with turret operations involving engineering analysis of dynamic loads and behavior to demonstrate the working of the turret unseating and rotating mechanisms. Figures 7 through 10 show selected models.
. . . AND FINALLY SAILING AGAIN
By applying the same exacting procedures used in the development of ships' hydrostatic, hydrodynamic, ship motion, maneuvering and seakeeping characteristics for ship handling simulators (see Figure 3., above), the Monitor was then launched in a virtual ocean subject to changing weather conditions, sea states, sea direction, and light conditions. She then "sailed" (under real-time, man-in-the-loop control) through various maneuvers in different environmental conditions.
Resurrected from her watery grave, the Monitor can set sail and will soon do battle again, in a computer generated virtual environment, commanded by young boys, as well as old salts, eager to experience an exciting bit of history.
Figure 11 is intended to show that virtual restoration is the corollary of virtual prototyping, making it possible to bring the past into the present and make it part of our future because of the power of communication and the deepening of understanding which visualization offers. High performance visualization is revolutionizing the way we can perceive and comprehend computer-generated data.
Our next challenge maybe should be to concentrate on one of the most dramatic and best remembered events of the Civil War, the naval battle between the USS Monitor and the CSS Virginia, formerly the Merrimack, captured by the artist Carl Beuder; see Figure 12. Although quite colorful, such display, as the primary representation of the past, could promote a superficial and possibly distorted picture of historical facts.
Since historic restoration must be viewed as a serious scientific and engineering endeavor, the objects must be modeling precisely in terms of their dimensions and geometrical representations. State-of-the-art computer-aided design tools can achieve this. And behavior must be in strict accordance with the laws of physics. Not only are these laws encoded in our computer-aided engineering programs, the resulting data are calculated that real-time responsiveness of the visual scene can be achieved. The possibilities are limitless.
The work discussed herein was, in part, sponsored by a grant from the National Center for Preservation Technology and Training (NCPTT), awarded to the National Preservation Institute (NPI). James C. Massey, its Executive Vice President and Advanced Marine's Fred M. Robinette, Director of Cultural Resources, made major contributions. Gordon Green, edited this paper and also supported the effort, as did Karl Leodler, Jerry Miller, David Wood, and Jacek Mazurkiewicz.