Kevin Scott
IPS Technical Committee Chair
The Renaissance Center
Dickson, Tennessee, USA
Richard McColman
Morehead Planetarium
Chapel Hill, North Carolina, USA
[reprinted from the Planetarian,
March 1999]
One of the primary charters for the IPS Technical Committee
is to review the range of competing full-dome video systems that
have recently become available, develop some sort of evaluation
metric, and attempt to define a set of standards that would help
manufacturers address compatibility issues for content production
and presentation. To that end, we are beginning the process of
looking at the major systems, each in detail. In this quarter's
column we'll give a comprehensive overview of the major technologies
involved, discuss two prevailing architectures, and review a few
of the major systems.
Technology Overview
Let us begin by saying that one could easily write much more on
this subject than we have space for here, and that this overview
is simply a brief introduction to some of the technologies and
terms that may appear in a discussion of full-dome video systems.
Also please keep in mind that we, the members of the IPS Technical
Committee, are not equipment vendors. We are looking at these
systems as potential customers in light of our collective expertise.
Furthermore, the IPS Technical Committee will not attempt to recommend
one system or another. Our main focus is to disseminate information
and to encourage the major vendors to create interoperable systems.
There are several companies that provide full-dome video systems
in a variety of formats. Some of the major vendors include:
ElectricSky™ Spitz, Inc.
Virtuarium GOTO Optical Mfg., Co.
V-Dome Trimension, Inc.
VisionDome™ Alternate Realities Co.
StarRider™ Evans & Sutherland
SkyVision Sky-Skan, Inc.
The actual physical setup varies from system to system, although
there are some similarities. Most of the options use multiple
video projectors and some form of edge-blending technology to
create a seamless video image over the entire surface of a planetarium
dome. Only Alternate Realities offers a single-lens system for
smaller theaters. To generate images, some systems use a graphics
super computer and others use off-the-shelf hardware and software
solutions. Finally, there is a wide range of control and automation
mechanisms, audience response sub-systems, and production philosophies.
There are two primary architectures in all-dome video systems:
real-time and offline (also known as "pre-rendered").
Real-time systems use massive amounts of processing power to generate
every image "on-the-fly." Offline systems render video
out to a storage medium (hard disk, tape, laserdisc) and then
play back as needed. Each architecture has its own merits, but
the larger question of which type of system a theater might choose
is probably more philosophical or financial in nature, rather
than technical.
Real-time architectures have their roots in high-end flight simulator
displays. Historically, these Image Generators (IGs) were specifically
designed to recreate out-of-cockpit views for pilots, ground warfare,
and other military training scenarios. Modern IGs provide a more
general-purpose approach to graphics and can now reproduce wider
range of content.
Production with real-time systems involves creating 3D graphics
models for every object in your "show." These models
are then given texture and color, and are placed in a three-dimensional
space the "world." Over time, objects can move
from one place to another, change in size and shape, and fly in
and out of the audience's view. In the spirit of flight simulators,
the audience's viewpoint can also change over time, allowing for
tremendous production freedom and graphic realism.
Real-time systems compute images as fast as they can hopefully
producing images at more than 30 frames-per-second (fps). Depending
on the complexity of the show sequence, real-time frame rates
may vary, resulting in motion that can be very smooth in some
places and jerky in others. With careful production, though, these
systems can produce consistent, smooth motion.
Since real-time architectures generate images on-the-fly, they
work very well in interactive environments. For example, with
StarRider™ from Evans & Sutherland, it is possible to
"fly" the theater with a single joystick, much like
one would fly a flight-simulator. Another important feature of
real-time image generation is the ability to manipulate program
content on the dome without having to refer to some sort of "preview"
or having to wait for animation sequences to render on a separate
computer. On the other hand, real-time systems are somewhat limited
in the complexity of the scenes that they can produce, and they
require very technically skilled modelers to create objects that
will be shown in a program. Further discussion of the merits and
challenges of various systems will be addressed within individual
product evaluations.
Offline (pre-rendered) architectures stem from recent advancements
in digital video production and non-linear editing systems. Desktop
video production and animation has become very popular in the
last several years. Today's systems can provide full professional
level capability at a fraction of the cost of yesterday's studio
gear. Witness television programs like Star Trek and Babylon 5,
along with blockbuster movies like Armageddon and Independence
Day; each of these productions used PC-based animation and video
editing systems to create visual effects.
Production with offline systems is similar to real-time. Objects
are modeled and textures are applied. One tremendous difference,
however, is the complexity of the models that can be used, at
the expense of time. An offline model can be as detailed as you
like, but you have to wait for the computer to render each image.
One advantage is that slow-time animation systems tend to be more
advanced (both in terms of interface and features) than the current
crop of real-time production software.
After selecting models and designing the animated sequences that
will make up your program, an additional step must be employed
to generate images for the dome. In a multi-projector situation,
frames of animation must be divided up, directed to the appropriate
projector, and synchronized with all of the other content. This
process is handled differently in each of the primarily offline
solutions evaluated here.
Near-real-time is another term that may be applied to some pre-rendered
systems. Given that all of your show content is prepared and placed
in random access storage (e.g. hard disk or laserdisc), it is
then considered to be online content. From there, individual frames
can be displayed at will, or in sequence, at almost any frame
rate. In this sense, pre-rendered content can mimic some of the
functionality of a real-time system.
Finally, there is a need to address standards between systems.
Currently, each vendor has a unique projector configuration, development
platform and imaging hardware. Some vendors support industry standard
tools like 3D Studio Max for modeling and animation, and After
Effects for compositing, although the final media format is different
for each system. That is, content created for one system can't
easily be used by another. This is especially true when moving
from real-time to offline or vice versa.
Perhaps a first step is to encourage vendors to agree on a common
projector configuration. Then we can concentrate on common media
formats and production standards. One example of vendors working
together was demonstrated at the most recent IPS conference in
London where Sky-Skan and Evans & Sutherland used the same
projectors to showcase SkyVision and StarRider. While each vendor's
content was very different, at least they were somewhat compatible
at the projector level. This kind of cooperation is beneficial
to both vendors and planetariums by expanding the library of available
content that can be presented in a theater.
Once there is a potential for projection compatibility it is necessary
to address the source material and production differences between
real-time and pre-rendered systems. As an example, we'll work
through a prototypical visual sequence and highlight a few of
the production considerations for both architectures. Our storyboard
snippet begins with the planet Saturn appearing on the limb of
our dome and zooming up to rest at front and center. After pausing
for a moment, we move towards the planet, dip through its rings
and fly on to Titan.
In a real-time environment, one would start by creating a sphere
to represent the planet Saturn and a disk for its rings. This
combination would probably be modeled several times, each with
a different level of detail (LOD). Because real-time systems are
limited in the amount of detail that can be displayed in any one
channel, (one channel = one projector) it is often necessary to
create simplified models to represent the object when viewed from
a distance. While zooming in towards the planet, we'd start with
the simplest model and transition between the others as it got
closer. The key is to develop models with the minimum number of
polygons necessary to achieve the desired effect.
Texturing the planet's surface isn't much of a challenge
one can find very accurate texture maps that will work nicely.
The rings are a bit more difficult. Designing a 2D texture for
the rings as viewed at a distance is not trivial, but designing
a series of textures to make the rings three-dimensional when
we move through them is downright hard. Unfortunately, a real-time
system could not possibly handle a model of every individual clump
of material in the rings and most real-time systems don't
support particle animation (an algorithmic method for generating
lots of tiny objects without having to explicitly model every
single one). In this case you'll most likely use a collection
of flat polygons with custom texture and transparency maps.
Once all the models are complete and textured, they must be translated
into the desired image generator format and downloaded to the
IG and to a show-control workstation. Once everything is "installed",
then comes the task of positioning models and preparing flight
paths for both the objects and/or the view camera. Those details
are very system-specific and are beyond the scope of this article.
In any case, once everything is roughly positioned and timed,
you're ready to finalize the sequence and move on.
To replicate this same scene in an offline environment, you again
start with basic models and textures. This time you don't have
to worry about level-of-detail models and polygon counts (though
these techniques can save you some rendering time). There are
also a number of "special effects" that you can add
in the offline system not currently available with real-time.
For example, you might develop a complex particle system to represent
the rings where all of the individual particles are moving independently
and realistically with the proper gravitational effects. You might
also add layering effects to the planetary surface to simulate
cloud layers. All these effects add rendering time, but they also
add a stunning amount of realism to the finished sequence. Finally,
the tools for creating object paths and camera paths are far superior
to most real-time show production software. Furthermore, in most
cases you can do all of your modeling, animation, and rendering
in one software package, on one computer. Real-time often requires
you to work with separate modeling, animation, and control packages,
and several different computer systems.
As you read through the following product reviews, keep in
mind that the technological issues of all-dome video are just
one small part of the equation.
Regardless of which system you may prefer from a technical standpoint,
there may be larger, more difficult questions to pose:
· Can I afford it?
· Will it help further the goals of my planetarium?
· Will it help me reach my audience more effectively?
You should also consider the time and money you'll spend on maintenance
and production. Another important consideration is whether you
have the creative and technical talent on your staff to effectively
use the system, or if you prefer to use external production houses
and private consultants. Any full-dome video system will more
than likely require at least two, perhaps three full-time employees
with very specific skill sets. The potential for these systems
is great, but they require a significant resource commitment.
SkyVision Product Review
This review does not constitute a recommendation nor endorsement
for any product or company.
SkyVision
Sky-Skan, Inc.
51 Lake Street
Nashua, New Hampshire 03060-4513 USA
Contact: Steve Savage
office@SkySkan.com
+1 800 880 8500
http://www.SkySkan.com
Evaluation Setup:
Cabletron, a large hardware vendor in the networking business,
hired Sky-Skan, through a series of subcontractors, to produce
and operate a demonstration program for Cabletron at the recent
Networld & Interop show in Atlanta, Georgia USA. The program
was given in a small 27-ft (8.2m) vacuum dome produced by ProDome
(Antti Jannes & Co. in Finland). In addition, there was a
Digistar II instrument, several moving-mirror incandescent fixtures,
and an infra-red sound system. As an aside, the seats were from
an automobile manufacturer and were very comfortable! Sky-Skan
also demonstrates SkyVision in their 30-ft (9.1m) dome in Nashua.
SkyVision currently consists of six Barco video projectors (with
outboard line quadruplers) for imaging on the dome. Five projectors
form a continuous horizon image, and the sixth projector forms
a "cap" that fills in the zenith. Each projector was
mounted underneath the springline of the dome. SkyVision, as assembled
in Atlanta, used Barco 801s projectors running at approximately
80% brightness. Sky-Skan also offers a high definition system
called SkyVision HR. Using the same configuration, this system
makes use of six Barco 1209s projectors. The digital video workstations
that feed the projectors have an initial on-line video playback
capacity of approximately 25 minutes and the native resolution
for each frame of video is 1726 x 1296 pixels. This yields an
image resolution approaching that of an IMAX frame across the
dome.
All of the projectors are accessed through the SPICE automation
system and each can function as a stand-alone unit along with
providing SkyVision output. This makes the system extremely flexible
when it comes time to incorporate more traditional video sources
(e.g. laserdisc, DVD, and tape formats) into a program.
Producing the images were six PC compatible computers, each
with a compressed video output card. In addition, the "zenith"
computer also had a SMPTE timecode generator, and an additional
card that delivered eight channels of digital audio for the show's
soundtrack. Each machine also had a removable storage unit with
a 9GB hard disk.
SPICE automation controls the SkyVision system, allowing programmers
to search for and play from individual frames of video, and to
play segments by name. The six-computer configuration is fairly
flexible, and may change in subsequent revisions of the system.
One advantage of keeping all six computers is that when it comes
time to render new footage, you can have six processors working
on the job.
In its current configuration, SkyVision supports two hours of
online storage. That's two hours of full-dome imagery without
changing disk drives. There are other storage options that can
provide up to eight hours of online video if needed. Since the
system uses removable technology, it is just as easy to swap in
a new set of drives for additional content. In any case, SkyVision
content storage is very flexible.
SkyVision supports interactivity through Sky-Skan's proprietary
hardware/software combination, along with some creative pre-production.
Since all of the content is pre-rendered and stored to hard disk,
multi-path programs (where the audience chooses various topical
segments during the course of the show) are quite simple to execute.
In fact, when compared to laserdisc, hard disk based video can
offer faster search times and more flexible control over playback.
More advanced forms of interactivity are also possible, though
it may require some extra effort during pre-production to assemble
all the content in a meaningful way.
The production process for SkyVision is relatively straightforward;
the magic is in the software. Sky-Skan has produced a clever production
tool that can take a computer image file and dice it up such that
it can be displayed as a whole by the SkyVision projectors. You
can use almost any image, though to achieve full-dome video you
will probably use a fish-eye lens (either real or virtual) to
generate an appropriate hemispherical representation of the subject.
Perhaps the two most common ways of producing SkyVision images
are via animation and compositing. When creating animated sequences,
the renderer is set up with a virtual camera that mimics a fish-eye
lens. This compensates for the distortion that occurs when projecting
onto a hemispherical screen. The detail of an animated sequence
is limited only by time and the sophistication of your rendering
software. It is also possible to use video and film footage shot
in more familiar rectangular formats. Using a compositing tool
(e.g. Adobe After Effects) one can stretch and position footage
for use with SkyVision. Note that since the date of this review,
Sky-Skan has made progress on streamlining the SkyVision production
process and has integrated additional content development tools.
SkyVision Strengths & Criticisms
Probably the most important technical considerations to address
are image quality, content production, and maintenance. The full-dome
image generated by SkyVision is surprisingly good, but varies
with content. With proper alignment, the seams between projectors
are nearly invisible. Depending on the image being projected,
sometimes the seams are not detectable at all. Projector alignment
will drift with time, though, and will likely require regular
adjustments to maintain the best image. High-detail, natural footage
such as Earth-bound panoramas seem to be more forgiving than some
animated sequences when it comes to detecting misalignments. Edge
blending between the five horizon projectors is excellent. Edge
blending inconsistencies between the zenith projector and the
others is much more noticeable. As with any multi-projector system,
the "soccer ball" effect is unavoidable when viewing
large, bright, low-detail areas such as a daytime summer sky.
(Keep in mind that this review was conducted in an inflatable
dome, and it is nearly impossible to accurately align multiple
projectors in such an environment - actual installations provide
much better results.) Given a bit more time, the engineers at
Sky-Skan say they can tune the image blending algorithms to minimize
the visual impact. Content is perhaps the largest factor in evaluating
image quality. Some material looks absolutely wonderful on SkyVision,
while other sources highlight its weak points. Our guess is that
this effect has as much to do with psychology and the human visual
system as it does with the technical aspects of multi-image projection.
Some planetarians who have used large format video projectors
may feel a bit underwhelmed by the brightness offered by CRT based
systems, especially in larger domes. Thankfully, this isn't so
much of a problem when using an all-dome video system by itself.
That is, when the eye can't compare between a smaller, brighter
projector and a larger, more dim image, the perceived contrast
ratio is very high and the image appears to be quite acceptable.
For mission critical applications, the image brightness issue
can be overcome by doubling the number of projectors, effectively
having two projectors per frame and having an instant backup for
the theater.
It may occur that while producing an animated sequence for SkyVision,
you spend all night rendering only to put the result up on the
dome and find that it's not acceptable, for whatever reason. Careful
planing and pre-production can minimize these troubles, but it's
still a fact of life. To help alleviate this problem, one might
do some production work in the dome itself, using one of the SkyVision
projectors as a preview monitor. Then it is possible to adjust
colors, intensity, detail, alignment, etc. such that it looks
best when viewed on the dome, rather than on a computer screen.
Perhaps the greatest strength of SkyVision is the ability to produce
detailed, Hollywoodstyle imagery with well known tools. Granted,
the time required to render complex scenes is substantial, but
it's the realism that modern audiences demand. Another strength
of SkyVision is that it takes a software approach to solving projection
geometry and overlap issues. This lowers the cost to the end user
because software is easy to reproduce and upgrade and does not
rely on more expensive proprietary "black box" hardware.
SkyVision is offered in full and partial dome configurations.
The first SkyVision installation was unveiled at the Houston Museum
of Natural History's Burke Baker Planetarium on December 11, 1998.
StarRider Product Review
This review does not constitute a recommendation nor endorsement
for any product or company.
StarRider™
Evans & Sutherland
600 Komas Dr.
Salt Lake City, Utah 84108 USA
Contact: Jeri Panek
jpanek@es.com
+1 801 588 1000
http://www.es.com
Evaluation setup:
The Evans & Sutherland Digital Theater division has constructed
a demonstration and development theater at their headquarters
in Salt Lake City, Utah. This theater features a 36-ft (11m) variable
tilt Astro-Tec dome, Sky-Skan automation and sound reinforcement,
a Digistar II digital planetarium, and a full dome StarRider projection
system.
StarRider is currently based on the ESIG (Evans & Sutherland
Image Generator) and the PRODAS display system from SEOS. PRODAS
consists of six specially modified Barco CRT video projectors
and a proprietary edge blending system to create a seamless dome
image. The projectors are arrayed in a five-segment panorama with
a sixth projector filling in at the zenith. (This configuration
is very similar to SkyVision, with some differences in projector
placement.) StarRider projectors normally reside in a cove space
or projection gallery such that the front lenses sit just beneath
the dome springline. PRODAS comes with a rather elaborate remote
control panel that is used to administer all aspects of projector
setup and operation. Unfortunately, the unit is not immediately
compatible with any automation system; that functionality may
arrive shortly.
With the addition of a video source switcher, StarRider can accommodate
other input sources (e.g. laserdisc, DVD, SkyVision, and tape
formats). Using these alternate sources and some creative animation
techniques, it is theoretically possible to create non-real-time
content for playback on StarRider. It is also possible to turn
off the edge-blending hardware. In effect, this makes each projector
behave as a "normal" Barco and provides six discreet
channels of video.
The graphics muscle behind StarRider is the Evans & Sutherland
line of image generators. As previously mentioned, the current
version of StarRider ships with the ESIG - a proven technology
that is used extensively in other E&S simulator product lines.
StarRider is also available with the new Harmony and Ensemble
image generators, both from E&S. Ensemble will come in at
the lowest price point, using custom PC-based graphics technology.
Harmony will offer the highest performance and image quality.
Harmony uses several proprietary graphics engines to generate
the six simultaneous video streams that drive StarRider. The IG
is based on a number of custom chip designs and runs under a specially
designed real-time operating system which results in unmatched
performance. Harmony supports a number of breakthrough graphics
technologies such as texture sharpening, real-time Phong shading,
and a multisample depth buffer. Suffice it to say that Harmony
is a very complex piece of engineering that is still in its infancy.
I strongly recommend that you explore the E&S website if you're
interested in these and other technical details of Harmony.
FuseBox is the software product that controls the Harmony IG and
integrates the entire StarRider system. FuseBox is a show production
and show control tool that brings together models, textures, and
other assets, into a visual scripting environment. Show elements
respond to system and user definable events (e.g. time cues),
and "paths" help define object motion. In addition,
FuseBox is the hub of StarRider's interactive capabilities. StarRider
uses flight sticks and an armrest keypad for audience participation.
FuseBox is a rapidly evolving tool that is being tuned to the
program development needs of StarRider. Its learning curve is
steep, but therein lies its power.
StarRider audio is handled by SawPro which is a commercial multitrack
audio editor and playback system. SawPro can support up to 32
tracks of simultaneous audio playback provided that you have enough
sound cards in your host computer (a Pentium class system with
at least 128Mb RAM). SawPro is the SMPTE show source for StarRider
and is triggered by FuseBox via MIDI. In case you're wondering,
a 20 minute show with six audio channels requires about 650Mb
of disk space if the material is stored at CD quality (44.1KHz
sample rate, 16 bit resolution). As with most hard disk based
audio systems, there is no wait for tape rewinding and the system
can instantaneously jump to any place in the soundtrack
quite a boon during production.
The production process for StarRider is somewhat complex. Each
task, in and of itself, is not overly difficult, but each has
its own separate challenges. To begin, all of the visuals in a
show must be modeled and textured. The modeling process can be
done with tools like 3dStudio Max and MultiGen. The challenge
is to create models that will work well in a real-time architecture.
Perhaps the most important point is that models should have low
polygon counts. In the process of creating textures, one must
consider how colors will change when viewed on a large screen
display, the effects of transparency, along with the physical
size and image complexity of the texture. There are substantial
differences when modeling for offline or real-time systems.
Once all the assets are generated, the next step is to begin organizing
and developing the show in FuseBox. Models are positioned and
oriented in the virtual world, given flight paths and other attributes,
and events are timed to match appropriate script and score cues.
During the course of production, one must keep in mind the capabilities
of the real-time IG. In order to maintain image frame rates, a
limited amount of detail may be present in each of StarRider's
six video channels.
StarRider Strengths & Criticisms
StarRider shares most of the basic technical challenges found
in multi-projector all-dome video systems; image quality, content
production, and maintenance. StarRider's image quality is a function
of content, production technique, and projector tuning. Visuals
must be well modeled, strategically placed, and motion must be
scripted with care. Harmony and the other E&S IGs are relatively
forgiving technologies, but they do have limits when it comes
to the complexity and placement of StarRider visuals. Specifically,
there is a limit on the amount of detail that can be displayed
in any one channel of the IG (recall that StarRider is a six-channel
system - one channel per projector.) Furthermore, aligning and
color matching the StarRider projectors is a challenging process.
In order to maintain the best image, the projectors will most
likely require bi-weekly adjustments. It is important to note
that when the system is properly tuned, the resulting image is
seamless and very pleasing to the eye.
Developing StarRider content requires a staff of creative and
skilled professionals. The terminology and technical challenges
of real-time are daunting. There's also a steep learning curve
when it comes to the highly specialized software used to create
and control models. Thankfully, one can use popular software like
3D Studio Max to create models, but one must use FuseBox to manipulate
them within the context of a show. Still, the very best StarRider
shows will be produced by those who have a firm grasp of real-time
modeling concepts.
Perhaps StarRider's greatest technical achievement is truly interactive
production and presentation. Interactively placing and moving
visual elements on the dome is a relatively new production model
and one that offers a tremendous amount of creative freedom. Furthermore,
the real-time processing of StarRider allows one to develop audience
interfaces that are unique and robust.
StarRider is normally sold as a complete package with dome, projectors,
Digistar II digital planetarium, sound system, interactive hardware,
effects, automation, and software. StarRider and Digistar II work
well together on the dome, but they are wholly separate development
environments. E&S currently offers full and partial dome StarRider
systems.
The first StarRider installation was unveiled at Chicago's Adler
Planetarium on December 4, 1998.
ElectricSky Product Review
This review does not constitute a recommendation nor endorsement
for any product or company.
ElectricSky™
Spitz, Inc.
PO Box 198, Route 1
Chadds Ford, PA 19317 USA
Contact: Jon Shaw
jshaw@spitzinc.com
+1 610 459 5200
http://www.spitzinc.com
Evaluation setup:
Spitz has several demonstration domes at its headquarters in Chadds
Ford, Pennsylvania. ElectricSky™ is currently housed in their
40-ft (12.2m) dome (10 degree tilt). The theater also showcases
a Spitz planetarium instrument, Spitz's new ATM-4 automation system,
and a full complement of all-sky and special effects projectors.
ElectricSky is offered in several configurations. To be more correct,
ElectricSky is a member of a family of products called ImmersaVision™,
an immersive multimedia theater system developed by Spitz. All-dome
(immersive) video is just one aspect of ImmersaVision. Currently,
the most extensively supported suite of products include ElectricHorizon
and ElectricSky. For this review, we are taking a look at Electric
Sky as configured with three projectors providing a 200 x 60 degree
field-of-view. Spitz also offers a four-projector system (panorama
with top-cap) and a seven projector full-dome array. ElectricSky
uses newly-developed Electrohome dome projectors with advanced
geometry correction and edge blending technologies from Panoram.
The entire system is integrated within the ATM-4 automation software,
allowing random video source selection, routing, and output format.
ElectricSky provides support for CRV, laserdisc, DVD, tape, digital
disk recorders, and workstation source material. ATM-4 also automates
the edge blending hardware such that blended and non-blended source
can be displayed within the same program.
Spitz developed a 10 minute demonstration program to showcase
the ImmersaVision format. The first performance was delivered
from a trio of CRV discs, and the second from DVDs. Without a
side-by-side comparison, it's difficult to see any differences
between the two source formats; both were of excellent quality.
Spitz is also exploring hard disk based storage options with an
eye toward an integrated media server. Recording source material
to a CRV disk is relatively simple, but the disks hold less than
a half hour of video per side. On the other hand, DVDs hold much
more content but are currently somewhat expensive to create. Keep
in mind that almost any video playback format can be used and
the folks at Spitz seem to be generally flexible in supporting
customer-preferred equipment.
Audio can originate directly from the playback devices or from
a separate digital tape or disk recorder. ElectricSky uses the
5.1 surround sound standard from either encoded source or discreet
channels. The ElectricSky specification outlines a complete theater
treatment for sound reproduction, including speaker types, placement,
and reinforcement hardware.
ATM-4 automation controls all aspects of ElectricSky through a
new Windows interface. ImmersaVision content is treated as a single
playback system with a standard set of control options. In addition,
ATM-4 supports interactivity via proprietary hardware.
ATM-4 automation controls all aspects of ElectricSky through
a new Windows interface. ImmersaVision content is treated as a
single playback system with a standard set of control options.
In addition, ATM-4 supports interactivity via proprietary hardware
(audience responders) and integrated software control. Like any
other pre-rendered architecture, interactive and multi-path programs
require a bit of pre-production effort. Any time the audience
is given a choice, two or more separate bits of content must be
generated and stored for real-time retrieval during the program.
The production process for the ImmersaVision format is greatly
simplified through the use of a number of custom utilities and
plug-ins that work with off-the-shelf production tools like AfterEffects,
and Photoshop. In addition, Spitz has developed a special plug-in
for the popular program 3D Studio Max, called ImmersaMax, used
to generate CG content for ImmersaVision.
ImmersaVision content can originate from a number of different
source material formats including film, video (HD and NTSC), panoramic
and hemispherical video and film, computer graphics, and still
images. In each case, a producer can chose the form of spherical
correction, if any, that needs to be applied to the source material
to ensure that it is displayed correctly on the dome. Spitz is
the only manufacturer that offers the ability to set an eyepoint
when correcting materials for display on a dome. That is, every
other system assumes that the viewer is seated in the very center
of the theater, which is usually the location of the planetarium
instrument. With Spitz's utilities, you can create a view that
is better suited to your particular theater layout.
Because ElectricSky uses hardware edge blending there are a number
of other image sources that can be considered. For example, you
can connect a desktop PC/Macintosh to the system, displaying the
computer desktop across three full projectors. ElectricSky can
also be driven by multi-channel visualization systems (from Silicon
Graphics, Intergraph, HP, etc.), and other real-time image sources.
This is a tremendous advantage during production because you can
test source material without having to split it up into three
separate frames and then apply soft edges for display. In the
case of ElectricSky, just open a window containing an image with
the correct aspect ratio and you're done! One might also imagine
playing video games on this enormous display, or perhaps seeing
every cell in a large spreadsheet. The possibilities are quite
exciting.
ElectricSky Strengths & Criticisms
Spitz's video panorama and ImmersaVision projection format are
more than a collection of software and hardware. In developing
these technologies, Spitz spent a great deal of time researching
large-format immersive displays. What they've come up with is
an extremely flexible system that can accommodate a diverse range
of source material and a production and presentation philosophy
that is based on the science of visualization. Of all the systems
reviewed thus far, Spitz has demonstrated the greatest amount
of technical flexibility and product forethought.
Spitz blends their video projectors with a 25% overlap, which
is a bit more than the other manufacturers use. This larger overlap
seems to have a positive effect on the resulting image, giving
the very best color blending, and absolutely seamless geometry
blending. Spitz also uses a circular top-cap, reducing the edge-blend
artifacts that can be quite harsh in a pentagonal cap (a la SkyVision
and StarRider).
Like SkyVision, ElectricSky production uses mostly off-the-shelf
tools and popular software packages for the manipulation and generation
of content. Spitz, however, has developed additional custom utilities
that allow an illustrator or animator to use virtually any software
package for content creation, even if that software doesn't support
spherical rendering or custom image warping! The other tremendous
advantage to ElectricSky is the ability to preview content on
the dome without having to split images and pre-blend. In fact,
you can use ElectricSky as a working desktop and produce images
right on the dome.
Spitz is currently focused on the three-projector ImmersaVision
format, with a sound philosophy and research to back up their
development efforts. They are working to build more support for
their full-dome video product, though Spitz did not demonstrate
full-dome capability during the review. There's no doubt that
a tremendous amount of content can be effectively displayed within
the ImmersaVision format. A planetarium, though, implies a complete
hemisphere and sometimes it's necessary to exploit the full dome
for maximum effect. Bear in mind that full-dome configurations
can be much more expensive, and they require more complex production
techniques. There is a clear trade-off and a planetarium's choice
may depend on cost, support, production and maintenance issues.
Formats like ImmersaVision provide a cleaner, more uniform image
than full-dome, are easier to maintain and operate, and provide
a very dramatic effect when used well. It's not an easy decision.
The first ElectricSky theater was unveiled at the Northern Lights
Centre in April of 1997. The Northern Lights Centre is located
in Watson Lake, Yukon Territory, Canada.
VisionDome Product Overview
This overview does not constitute a recommendation nor endorsement
for any product or company.
VisionDome is a system for projecting full-color, full-motion
graphics, created and manipulated in a 3-D computer environment.
The technology is most similar to that of StarRider, but instead
of using several video projectors to cover the dome, VisionDome
uses a single projector and fish-eye lens to achieve a full-dome
image. VisionDome is a real-time architecture that shares many
of StarRider's strengths and content development challenges.
Alternate Realities Corporation is located in North Carolina's
Research Triangle Park, nestled between the cities of Raleigh,
Durham, and Chapel Hill. Morehead Planetarium proved to be a convenient,
yet challenging test for their system in an actual, working planetarium
theater. (Until that time they had limited their activities to
using the technology in a small, demonstration dome as a stand-alone
system.) Besides the challenges of positioning the projector off-center,
such a demonstration would test the ability of the system to project
images over a much greater distance. Both the VisionDome and Morehead
staffs were initially skeptical about how well the system's images
would hold up projecting onto a 20.7-meter (68-foot) dome, but
felt, nonetheless, that the challenge would be informative in
evaluating VisionDome's capabilities and limitations.
After a couple of preliminary visits to evaluate the Morehead
theater environment, and to arrange for an adequate electrical
power feed, the VisionDome team arrived to conduct their test.
Their equipment included a 3-D graphics workstation and image
processor; a high-intensity, high-resolution video/graphics projector;
a specially-designed optical assembly for the 180-degree projection;
and a large, makeshift wooden stand for the projector.
On "test day", equipment setup was completed within
only a couple of hours of arrival. The large projector had been
placed on its stand, the long optical pipe - complete with integral
fisheye lens - was mated and aligned to the projector, and the
graphics workstation and processor was up and running. A few moments
later, the first VisionDome images were being drawn. A variety
of different images were displayed during the test, including
fractal-style images, a graphical Space Shuttle launch, and a
DNA double helix, among others.
The initial results were encouraging with a number of images that
showed a surprising degree of sharpness and clarity. Motion of
the manipulated "objects" was relatively smooth, with
very little jerkiness evident. Objects were projected with a variety
of background colors, but the best results were obtained when
objects were placed against a black background.
Of course, it was assumed that there would be difficulties associated
with the Morehead test. Some of the images displayed during the
test were quite "soft" in appearance. The VisionDome
people said this was because they were testing image-sequences
of a variety of resolutions. It was obvious that only the higher-resolution
images would be applicable for all-dome use. There was some distortion
visible in the images, taking the form of the image appearing
to rest atop a curved void of black extending about 75 degrees
in azimuth and about 10-15 degrees in altitude at the void's apex.
The VisionDome folks attributed this effect to an incorrect mechanical
adjustment between the projector and the lens pipe. They explained
that this would be easily correctable by re-machining the shim-plates
between the two components. However, the good news was that the
distortion that would normally be encountered by projecting images
off-center is easily corrected by loading a computer algorithm
into the graphics processor.
The main limitation seen during the test was Morehead's large
dome-size, which lowered the brightness, contrast, and overall
color-saturation of the images. In addition, Morehead's white,
high-reflectance dome further reduced the overall contrast of
many images - particularly those incorporating non-black backgrounds
- because of "cross-bounce". (This is a phenomenon familiar
to all-dome film people, and is why such theaters have gray domes
to reduce the overall reflectance, and thus, the cross-bounce
effect.) Both the VisionDome and Morehead personnel suspected
that lowered brightness, contrast, and color would be negative
factors in the test, but were, nonetheless, pleasantly surprised
that the images "held up" as well as they did. However,
because of these limitations, VisionDome, as currently configured,
is not optimized for large-dome applications. And given the need
for lowered dome reflectance, the system is probably best suited
for domes roughly 12-meters (40-feet), and smaller.
VisionDome Strengths & Criticisms
As with most of the systems under review, content for VisionDome
is a primary concern. VisionDome's graphics workstation and application
software appeared to be quite functional. However, since there
is currently little in the way of appropriate ready-to-go graphical
sequences for the system -particularly those which are astronomical
in nature - the burden appears to rest primarily on the shoulders
of the end-user. Facilities considering VisionDome or any other
similar graphical system for the planetarium must consider the
issue of content availability. With a trend toward smaller staffs
in planetariums these days, many facilities may be hard-pressed
to create original images for use in programs, given the staff-time
and expertise needed to generate even the simplest 3-D objects
and manipulated sequences. To that end, Mr. Galluppi and the engineers
at ARC are interested in approaching the planetarium community
as a potential market and looking for artists/designers to develop
visual content.
The Morehead demonstration should be looked at as a worst-case
scenario. Not only was the dome extremely large, but the system
was tested with an older generation of video projector. Newer
projectors from the same manufacturer can produce brighter, sharper
images at higher resolutions. The greatest potential for VisionDome
is in smaller theaters where the image can be most effectively
used.
Alignment and color balancing with VisionDome is greatly simplified
since there is only one projector and one lens. There are no bright
spots, overlap areas, or other alignment headaches to deal with.
While the system is not maintenance-free, it is much less expensive
to own and operate.
An ideal partnership would probably be to install a VisionDome
system into a college or university planetarium where staff and
students could make use of it as a visualization platform and
showcase for student graphics work. VisionDome is available in
a number of configurations and price-points.
Questions and comments regarding these reviews should be made
directly to the respective vendor or to the IPS Technical Committee:
Kevin Scott
IPS Technical Committee Chair
The Renaissance Center
Suite 400
719 East College Street
Dickson, TN 37055
+1 615 446 1985
kevin@rcenter.org
Production Software
3D Studio Max: www.ktx.com
Electric Image Animation System: www.electricimage.com
Lightwave: www.newtek.com
MultiGen real-time modeling tool: www.multigen.com
Reprinted from the Planetarian, Vol 28, #1, March 1999.
Copyright 1999 International Planetarium Society. For permission
to reproduce please contact Executive Editor, Sharon Shanks.
