·
Increasing amount of content (physical items), and at the same time a
decreasing storage space for the items
·
Memory institutions are relatively few in number, and unequally
distributed which causes inequities in what is chosen to be stored, and what is
accessible.
·
Access to content is severely limited due to travel costs. And again there are inequities due to many
groups having little to no funding.
·
Many antiquities are too fragile to travel, or to allow repeated
handling and exposure.
·
Handling of culturally sensitive materials may not be permissible or
appropriate.
·
Content items or sites are lost to natural hazards (floods, fires,
volcanoes, earthquakes), theft, warfare, or economic development.
There
are many advantages to digitizing content, both individual items and exhibits
(even the entire museum). Having a
digital copy of items or exhibits allows them to be accessed by anyone, at any
time, from any place. It allows any
number of people access at the same time.
It preserves a nearly complete record of the object, which can be
accessed without damaging the original.
3D digitization and display potentially solve all the challenges listed
above. The advantages that virtual
museums provide are listed below:
·
Imagery and spatial measurements are mechanically recorded and not
subject to human interpretation.
·
Everything can be recorded, in complete detail, in their original
setting, with limited human effort.
·
Precise, repeatable measurements are made that are equally or more
precise than human measured ones.
·
Objects can be viewed virtually and virtually dissected for study for
any amount of time, with no cost or damage to the content.
·
Morphological comparison of related material is facilitated through
qualitative visual comparisons or quantitative shape-based comparisons.
·
The system is non-invasive, in that it does not touch or affect the
samples or site. This is important for
conservation.
·
Because the data is digital it can be conveniently archived and made
available anywhere, anytime, to anyone 24/7/365.
·
Different interfaces, or visualizations, can be provided depending on
the observer, their task, and the material.
For instance a scholar may desire a shape comparison display while a museum
visitor may wish to simply browse the different exhibits.
The equipment used for
scanning the scenes is the DeltaSphere-3000 (3rdTech,
Computer control of the
internal positioning motors at the base, and the revolving mirror allow the
DeltaSphere to automatically scan a complete room or scene with the laser
rangefinder. The default setting of
13.33 samples/degree is appropriate for scanning rooms or large scenes for
virtual museum digitizations. Using this
setting
Figure
1 DeltaSphere 3D Scene Digitizer
the scanner records the
range and position of several million sample points for distances up to 40ft
(12.2m) from the scanner in less than 20 minutes. The acquired set of sample points can be
automatically converted to a simple 3D model. This model can be rotated,
scaled, and displayed from arbitrary viewpoints. It can be used as input to
other software packages for creating realistic 3D images and animations. Finally, range data from multiple scans can
be combined to create a single 3D model. For example, scans of multiple rooms,
or multiple parts of the same room can
be combined to create a complete detailed model.
The second step is to use a
professional digital camera to capture the color image data for the scene. We used a Fuji FinePixS2Pro with
non-fisheye lens AF Nikkor ED 14mm
f/2.8D for the examples in this paper.
The captured color digital images are correlated with the laser range
finder spatial points. This allows the
generation of very realistic views of the 3D scene from any angle. An example of a static 2D rendered image from
one viewpoint is seen in Figure 2. While most range finder based digitization
systems can provide 3D scene views, the images are generally of lower
quality. The 3D environment recorded by
the DeltaSphere 3000, however, is of very high quality, nearly
indistinguishable from a photograph of the scene as seen in figure 2. While static 2D images can be used to view the
digitized 3D environment, it is more effective to view it using real-time
viewing applications that display the 3D scene on a 2D computer display
maintaining some of the 3D visual cues (lighting, shading, obscuration, stereo
(if stereo viewing glasses are used), user controlled changing of viewpoint). This supports a virtual reality experience
where users can actually feel as if they are in the museum, as opposed to
seeing photographs of the museum. Techniques that photographically capture
scenes, or that do not integrate the color image textures with the range finder
data cannot provide such visualizations.
Figure 3 shows the actual sample data points underlying the
visualization seen in figure 2. The output of the process of combining the
color texture from the digital photographs with the laser range finder sample
points is a VRML format data file. This
is a standard format for texture mapped polygons, and supported by most 3D
viewing applications.