eScience Lectures Notes : eScience Computer Graphics

Slide 17 : 1 / 28 : Display Technologies

Display Technologies


Video Displays

Cathode Ray Tubes (CRTs)

Vector Displays

Raster Displays

( Character Buffer )

Color Video

Raster Display Summary

Comparison CRT / LCD

Liquid Crystal Displays (LCDs)

Reflective and Backlit LCDs

Active Matrix LCDs

Plasma Display Panels

Field Emission Devices (FEDs)

Digital Micromirror Devices (DMDs)

Light Emitting Diode (LED) Arrays

Other Flat Panel Display Technologies (FPD)

Overhead projectors

Immersion and VR

Projection Technology

Following issues

Slide 18 : 2 / 28 : Display Devices

Display Devices

Former lesson : importance of computer graphics in today world

As seen in the first lecture, there is a widespread recognition of the power and utility of computer graphics in virtually all fields, a broad range of graphics hardware and sofware are available. We will begin by having a look at the displays device.

Slide 19 : 3 / 28 : Display Technologies

Cathode Ray Tubes (CRTs)

  • Most common display device today

  • Evacuated glass tube

  • Heating element (filament)

  • Electrons attracted to focusing anode cylinder

  • Vertical and Horizontal deflection plates

  • Beam strikes phosphor coating on front of tube


CRTs, or video monitors, are the most common output device on computers today.
The figure below illustrates the basic structure of a CRT.

A CRT is an evacuated glass tube, with a heating element on one end and a phosphor coated screen on the other.
When a current flows through this heating element, called a filament, the conductivity of the metal filament is reduced due to the high temperature. This cause electrons to pile up on the filament, because they can not move as fast as they would like to. Some of these electrons actually boil off of the filament.
These free electrons are attracted to a strong positive charge from the outer surface of the focusing anode cylinder (sometimes called an electrostatic lens). However, the inside of the cylinder has a weaker negative charge. Thus when the electrons head toward the anode they are forced into a beam and accelerated by the repulsion of the inner cylinder walls in just the way that water is speeds up when its flow though a smaller diameter pipe. By the time the electrons get out they're going so fast that they fly past the cathode they were heading for.
The next thing that the electrons run into are two sets of weakly charged deflection plates. These plates have opposite charges, one positive the other negative. While their charge is not strong enough to capture the fast moving electrons they do influence the path of the beam. The first set displaces the beam up and down, and the second displaces the beam left and right. The electrons are sent flying out of the neck of the bottle, until they smash into the phosphor coating on the other end of the bottle.
The impact of this collision on the out valence bands of the phosphor compounds knocks some of the electrons to jump into the another band. This causes a few photons to be generated, and results in our seeing a spot on the CRT's face.

Slide 20 : 4 / 28 : Vector Displays

Vector Displays

  • Oscilloscopes were some of the 1st computer displays

  • Used by both analog and digital computers

  • Computation results used to drive the vertical and horizontal axis (X-Y)

  • Intensity could also be controlled (Z-axis)

  • Used mostly for line drawings

  • Called vector, calligraphic or affectionately stroker displays

  • Display list had to be constantly updated
    (except for storage tubes)

Tektronix 4014
Tektronix 4014

CRTs were embraced as output devices very early in the development of digital computers.

There close cousins, vacuum tubes, were some of the first switching elements used to build computers. Today, the CRT is a the last remaining vacuum tube in most systems (Even the flashing lights are solid-state LEDs). Most likely, oscilloscopes were some of the first computer graphics displays. The results of computations could be used to directly drive the vertical and horizontal displacement plates in order to draw lines on the CRT's face. By varying the current to the heating filament the output of the electron beam could also be controlled. This allowed the intensity of the lines to vary from bright to completely dark.
These early CRT displays were called vector, calligraphic or affectionately stroker displays. The demonstration above gives some feel for how they worked. By the way, this demo is an active Java applet. You can click and drag your mouse inside of the image to reorient the CRT for a better view. Notice the wireframe nature of the displayed image. This demo is complicated by the fact that it's a wireframe simulation of a wireframe display system. Notice how the color of the gray lines of the CRT vary from dark to light indicating which parts of the model that are closer to the viewer. This technique is called depth-cueing, and it was used frequently on vector displays.
The intensity variations seen on the teapot, however, are for a different reason. Eventually, the phosphors recover from their excited state and the displaced electrons return back to their original bands. The glow of the phosphor fades. Thus, the image on the CRT's face must be constantly redrawn, refreshed, or updated. The two primary problems with vector displays are that they required constant updates to avoid fading, thus limiting the drawn scene's complexity, and they only drew wireframes.

Slide 21 : 5 / 28 : Raster Displays

Raster Displays

  • TV boomed in the 50s and early 60s
    (they got cheap)

  • B/W TVs are basically oscilloscopes
    (with a hardwired scan pattern)

  • Entire screen painted 30 times/sec

  • Screen is traversed 60 times/sec

  • Even/Odd lines on alternate scans
    (called fields)

  • Interlace - a hack to give

    • Smooth motion
      on dynamic scenes

    • High Resolution
      on static scenes

    • Optimize bandwidth

During the late 50s and early 60s, broadcast television, really began to take off. It had been around for a while, but it didn't become a commodity item until about this time. Televisions are basically just oscilloscopes. The main difference is that instead of having complete control over the vertical and horizontal deflection, a television sweeps its trace across the entire face in a regular fixed pattern (the actual details are slightly more complicated, but that's the jist of it). This scanning pattern proceeds from the top-left of the screen to the bottom-right as shown in the diagram.
The final result is that the entire screen is painted once every 1/30th of a second (33 mS) in USA and once every 1/25th in europe or in Australia.

Televisions were mass produced and inexpensive. For a computer to paint the entire screen it needs only to synchronize its painting with the constant scanning pattern of the raster. The solution to this problem was to add a special memory that operated synchronous to the raster scanning of the TV, called a frame buffer.
While televisions were cheap, memory wasn't. So there was a long period where the patterns were scanned out of a cheap high-density read-only memories, called character generators. The trick was to use a single 8 bit code to specify an 8 by 12 character pattern from the ROM, and with a few addressing tricks one could build a nice display (80 by 25 character) with only 2 kilobytes of memory. Thus the era of the CRT-terminal was born.

Slide 22 : 6 / 28 : Character Based Frame Buffer

Raster Display


In a raster display the path of the electron beam is hardwired. The computer must synchronize its "painting" of the screen with the scanning of the display. The computer only controls the intensity of the color at each point on the screen. Usually a dedicated section of memory, called the frame buffer, is used to store these intensity variations.



The simulation above is a Java applet that simulates the scanning of a raster display. Move the CRT wireframe (by clicking and dragging) in order to get a better feel.
There were a few attempts at building systems with downloadable or programmable character generators. And a few systems added an extra byte to specify the foreground and background colors of the character cell. Lots of tank/maze arcade games in the 70's worked this way. But by the late 70's and early 80's the price of memory started a free-fall and the graphics terminal was born. In a later lecture we'll go into a lot more detail about the notion of a framebuffer an how it is fundamental to modern computer graphics.

Slide 23 : 7 / 28 : Color Video

Color Video

Delta Electron Gun Arrangement

Color CRTs are much more complicated

  • Requires precision geometry

  • Patterned phosphors on CRT face

  • Aligned metal shadow mask

  • Three electron guns

  • Less bright than monochrome CRTs

In-line Electron Gun Arrangement

Color CRT's are more complicated than the simple monochrome models summarized before. The phosphors on the face of a color CRT are laid out in a precise geometric pattern. There are two primary variations, the stripe pattern of in-line tubes shown on the left, and the delta pattern of delta tubes as shown on the right.
Within the neck of the CRT there are three electron guns, one each for red, green, and blue (the actual beams are all the same color-- invisible). There is also a special metal plate just behind the phosphor cover front face, called a shadow mask. This mask is aligned so that it simultaneously allows each electron beam to see only the phosphors of its assigned color and blocks the phosphor of the remaining two colors.
The figure shown above shows the configuration of an example in-line tube. On page 44 of Hearn & Baker you'll see a similar diagram for a delta electron gun configuration
A significant portion of the electron beam's energy strikes the mask rather than the phosphors. This has two side effects. The shadow mask has to be extremely rigid to stay aligned with the phosphor patterns on the CRT face. The collision of electrons with metal mask causes the mask to emit some of it absorbed energy as electromagnetic radiation. Most of this energy is in the form of heat, but some fraction is emitted as x-rays. X-rays can present a health hazard. This wasn't a large problem for television because the intensity of the x-ray radiation falls off quickly as you move away from the screen. However, computer monitors are supposed to be viewed from a short distance. This health concern along with the high voltages and power dissipations of CRTs has motivated the development of new display technologies.


For more information on CRTs check out the following links:

The History of the Cathode Ray Tube



The Scoop on CRTs






Slide 24 : 8 / 28 : Cathode Ray Tubes Summary

Raster Display Summary


  • Requires screen-sized memory array

  • Discrete spatial sampling (pixels)

  • Moire patterns result when shadow-mask and dot-pitch frequencies are mismatched

  • Convergence (varying angles of approach distance of e-beam across CRT face)

  • Limit on practical size (< 40 inches)

  • Spurious X-ray radiation

  • Occupies a large volume


  • Allows solids to be displayed

  • Leverages low-cost CRT H/W (TVs)

  • Whole Screen is constantly updated

  • Bright light-emitting display technology



Slide 25 : 9 / 28 : Comparison CRT / LCD

Comparison CRT / LCD

Cathode Ray Tubes

Liquid Crystal Displays (LCDs)


  • Fast repsonse (high resolution possible)

  • Full color (large modulation depth of E-beam)

  • Saturated and natural colors

  • Inexpensive, matured technology

  • Wide angle, high contrast and brightness



  • Small footprint (approx 1/6 of CRT)

  • Light weight (typ. 1/5 of CRT)

  • Low power consumption (typ. 1/4 of CRT)

  • Completely flat screen - no geometrical errors

  • Crisp pictures - digital and uniform colors

  • No electromagnetic emission

  • Fully digital signal processing possible

  • Large screens (>20 inch) on desktops


  • Large and heavy (typ. 70x70 cm, 15 kg)

  • High power consumption (typ. 140W)

  • Harmful DC and AC electric and magnetic fields

  • Flickering at 50-80 Hz (no memory effect)

  • Geometrical errors at edges


  • High price (presently 3x CRT)

  • Poor viewing angle (typ. +/- 50 degrees)

  • Low contrast and luminance (typ. 1:100)

  • Low luminance (typ. 200 cd/m2)


Slide 26 : 10 / 28 : Liquid Crystal Displays (LCDs)

Liquid Crystal Displays (LCDs)

Currently, the most popular alternative to the CRT is the Liquid Crystal Display (LCD). LCDs are organic molecules that, in the absence of external forces, tend to align themselves in crystalline structures. But, when an external force is applied they will rearrange themselves as if they were a liquid. Some liquid crystals respond to heat (i.e. mood rings), others respond to electromagnetic forces.
When used as optical (light) modulators LCDs change polarization rather than transparency (at least this is true for the most popular type of LCD called Super-twisted Nematic Liquid crystals). In their unexcited or crystalline state the LCDs rotate the polarization of light by 90 degrees. In the presence of an electric field, LCDs the small electrostatic charges of the molecules align with the impinging E field.
The LCD's transition between crystalline and liquid states is a slow process. This has both good and bad side effects. LCDs, like phosphors, remain "on" for some time after the E field is applied. Thus the image is persistent like a CRT's, but this lasts just until the crystals can realign themselves, thus they must be constantly refreshed, again, like a CRT.

The book Hearns & Baker is a little confusing in describing how LCDs work (pp. 47-48). They call the relaxed state the "On State" and the excited state the "Off State". Their statement is only true from the point of view of the pixels when the LCDs are used in a transmissive mode (like on most laptops). The opposite is true when the LCDs are used in a reflective mode (like on watches).

Slide 27 : 11 / 28 : Reflective and Backlit LCDs

Reflective and Backlit LCDs

Rather than generating light like a CRTs, LCDs act as light values. Therefore, they are dependent on some external light source. In the case of a transmissive display, usually some sort of back light is used. Reflective displays take advantage of the ambient light. Thus, transmissive displays are difficult to see when they are overwhelmed by external light sources, whereas reflective displays can't be seen in the dark.

You should also note that at least half of the light is lost in most LCD configurations. Can you see why?

Slide 28 : 12 / 28 : Active Matrix LCDs Active Matrix LCDs

Active Matrix LCDs (aka Thin Film Transistor (TFT))

The LCD's themselves have extremely low power requirements. A very small electric field is required to excite the crystals into their liquid state. Most of the energy used by an LCD display system is due to the back lighting.
It was mentioned earlier that LCD's slowly transition back to their crystalline state when the E field is removed. In scanned displays, with a large number of pixels, the percentage of the time that LCDs are excited is very small. Thus the crystals spend most of their time in intermediate states, being neither "On" or "Off". This behavior is indicative of passive displays. You might notice that these displays are not very sharp and are prone to ghosting. Another way to building LCD displays uses an active matrix. The individual cells are very similar to those described above. The main difference is that the electric field is retained by a capacitor so that the crystal remains in a constant state. Transistor switches are used to transfer charge into the capacitors during the scanning process. The capacitors can hold the charge for significantly longer than the refresh period yielding a crisp display with no shadows. Active displays, require a working capacitor and transistor for each LCD or pixel element, and thus, they are more expensive to produce.

TFT displays

Many companies have adopted Thin Film Transistor (TFT) technology to improve colour screens. In a TFT screen, also known as active matrix, an extra matrix of transistors is connected to the LCD panel - one transistor for each colour (RGB) of each pixel. These transistors drive the pixels, eliminating at a stroke the problems of ghosting and slow response speed that afflict non-TFT LCDs. The result is screen response times of the order of 25ms, contrast ratios in the region of 200:1 to 400:1 and brightness values between 200 and 250 cd/m2 (candela per square metre).
The liquid crystal elements of each pixel are arranged so that in their normal state (with no voltage applied) the light coming through the passive filter is 'incorrectly' polarised and thus blocked. But when a voltage is applied across the liquid crystal elements they twist by up to ninety degrees in proportion to the voltage, changing their polarisation and letting more light through. The transistors control the degree of twist and hence the intensity of the red, green and blue elements of each pixel forming the image on the display.
TFT screens can be made much thinner than LCDs, making them lighter, and refresh rates now approach those of CRTs as the current runs about ten times faster than on a DSTN screen. VGA screens need 921,000 transistors (640 x 480 x 3), while a resolution of 1024 x 768 needs 2,359,296 and each has to be perfect. The complete matrix of transistors has to be produced on a single, expensive silicon wafer and the presence of more than a couple of impurities means that the whole wafer must be discarded. This leads to a high wastage rate and is the main reason for the high price of TFT displays. It’s also the reason why in any TFT display there are liable to be a couple of defective’ pixels where the transistors have failed.
There are two phenomenon which define a defective LCD pixel:
A 'lit' pixel, which appears as one or several randomly-placed red, blue and/or green pixel elements on an all-black background, or
a 'missing' or 'dead' pixel, which appears as a black dot on all-white backgrounds.
The former is the more common and is the result of a transistor occasionally shorting on, resulting in a permanently 'turned-on' (red, green or blue) pixel. Unfortunately, fixing the transistor itself is not possible after assembly. It is possible to disable an offending transistor using a laser. However, this just creates black dots which would appear on a white background. Permanently turned on pixels are a fairly common occurrence in LCD manufacturing and LCD manufacturers set limits - based on user feedback and manufacturing cost data - as to how many defective pixels are acceptable for a given LCD panel. The goal in setting these limits is to maintain reasonable product pricing while minimising the degree of user distraction from defective pixels. For example, a 1024x768 native resolution panel - containing a total of 2,359,296 (1024x768x3) pixels - which has 20 defective pixels, would have a pixel defect rate of (20/2,359,296)*100 = 0.0008%.
TFT panels have undergone significant evolution since the days of the early,  Twisted Nematic (TN) technology based panels.

Slide 29 : 13 / 28 : Plasma Display Panels

Plasma Display Panels



  • Promising for large format displays

  • Basically fluorescent tubes

  • High-voltage discharge excites gas mixture (He, Xe)

  • Upon relaxation UV light is emitted

  • UV light excites phosphors

  • Large viewing angle

  • Less efficient than CRTs

  • Not as bright

  • More power

  • Large pixels (~1mm compared to 0.2mm for CRT)

  • Ion bombardment depletes phosphors

Plasma display panels (PDPs) are essentially a matrix of very small fluorescent tubes with red, green, and blue phosphors. As in ordinary tubes, a discharge is initiated by a high voltage which excites a mixture of inert-gases such as He and Xe. Upon relaxation, ultra-violet (UV) radiation is generated which excites the phosphors.
PDPs provide a large viewing angle since the phosphors emit light uniformly. A 40-inch PDP typically consumes about 300 W whereas the peak brightness is only 1/3 of that of a CRT consuming about half the power. Sealing and vacuum pressure support problems apply to PDPs as well, requiring thicker glass as the screen is enlarged. In addition, the discharge chambers have pixel pitches of more than 1 mm which makes it difficult to construct high-definition television (HDTV) and work-station monitors. By contrast, TFTLCDs, CRTs and FEDs may have pixel pitches as small as 0.2 mm.

Slide 30 : 14 / 28 : Field Emission Devices (FEDs)

Field Emission Devices (FEDs)

  • Works like a CRT with multiple electron guns at each pixel

  • Uses modest voltages applied to sharp points to produce strong E fields

  • Reliable electrodes proven difficult to produce

  • Limited in size

  • Thin, and requires a vacuum

Field Emission Display: a display technology which use vacuum tubes (one for each pixel) with conventional RGB phosphors.

Slide 31 : 15 / 28 : Digital Micromirror Devices (DMDs)

Digital Micromirror Devices (DMDs)

(aka Digital Light Processing / DLP / commercial name)

(A Micro-Optical Electromechanical Device - MOEMS - for Display Applications)

Texas Instruments

  • Microelectromechanical (MEMs) devices

  • Fabricated using VLSI processing techniques

  • 2-D array of mirrors

  • Tilts +/- 10 degrees

  • Electrostatically controlled

  • Truly digital pixel

Three Mirrors Project Image

Incoming light hits the three mirror pixels. The two outer mirrors that are turned on reflect the light through the projection lens and onto the screen. These two "on" mirrors produce square, white pixel images. The central mirror is tilted to the "off" position. This mirror reflects light away from the projection lens to a light absorber so no light reaches the screen at that particular pixel, producing a square, dark pixel image. In the same way, the remaining mirror pixels reflect light to the screen or away from it. By using a color filter system and by varying the amount of time each of the DMD™ mirror pixels is on, a full-color, digital picture is projected onto the screen.

  • Suitable only for projection displays

  • Gray levels via Pulse-Width Modulation (PWM)

  • Color via multiple chips or a color-wheel

  • Excellent resolution and fill-factor

  • Light efficient

  • Problems with stray light and flicker

SXGA DMD on Hand
SXGA device with black aperture: 1280x1024; 1,310,720 mirrors

DMD™ and Ant Leg
Micrographic photo of ant leg on the DMD surface. Each mirror is 16 µm2 with 1µm separation between pixels

Digital Micromirror Device: an array of semiconductor-based digital mirrors that precisely reflect a light source for projection display and hard-copy applications. A DMD enables Digital Light Processing and displays images digitally. Rather than displaying digital broadcast signals as analogue signals, a DMD directs the digital signal directly to your screen.

Slide 32 : 16 / 28 : Light Emitting Diode (LED) Arrays

Light Emitting Diode (LED) Arrays

  • Organic Light Emitting Diodes (OLEDSs)

  • Function is similar to a semiconductor LED

  • Thin-film polymer construction

  • Potentially simpler processing

  • Transparent

  • Flexible

  • Can be vertically stacked

  • Excellent brightness

  • Large viewing angle

  • Efficient (low power/low voltage)

  • Fast (< 1 microsec)

  • Can be made large or small

  • Tend to breakdown

A display device consisting of a series of carbon-based thin films sandwiched between two electrodes; one transparent (often glass). OLED technology holds promise because of the ability to tailor the organic molecules to vary color saturation, sensitivity, and other optical properties.

The operation of organic LEDs is similar to inorganic semiconductor LEDs. When two materials, one with an excess of mobile electrons the other with a deficiency, are place in close contact, a junction region is formed. When a small potential is applied, the resistance of this junction to the transport of electrons can be overcome. The motion of the electrons in an LED excites the electron on lower valance bands, causing them to move up or down into other bands. This configuration is unstable and the electrons quickly return to their previous state. This change in energy (induced by the electrons returning to their proper valence bands) causes a photon to be emitted.

Unlike crystalline semiconductors, though, these organic devices are made by depositing a thin-film layer from a solution or by a vacuum deposition process. They are not grown like a crystal, and they do no require a high-temperature process to dope them. This allows large areas to be processed, unlike typical semiconductor fabrication.

Several recent developments have stimulated significant interest in OLEDs. These include new materials and new processes. The performance of prototype systems has been very promising. It appears likely that commercial display products will appear in the near future.

OLEDs have many advantages. They are light-emitting, low-voltage, full-color, and have an easily produced electronic structure. All other light-emitting, flat panel technologies employ high voltages. The simple structure is clearly not a characteristic of other popular flat panel display types.
OLED development has progressed rapidly, but there is still much work to be done. Display lifetime remains a key issue with OLEDs. Many of the researchers already feel confident that these problems can be overcome.

Slide 33 : 17 / 28 : Other Flat Panel Display Technologies (FPD)

Other Flat Panel Display Technologies (FPD)


The one we have seen :
Light emitting diode arrays ( LED )
Organic luminescent displays ( OELD )
Micro-Optical Electromechanical Systems ( MOEMS )




Slide 34 : 18 / 28 : Overhead projectors

Overhead projectors : Some examples of commercial products



Nec : Short Persistence Phosphor CRT
MultiSync XG85S


NEC MultiSync GT series LCD projector




Barco :


Nec Projectors :
or :

Nec for the Wedge :

2 NEC Multisync XG75 : CRT Projector

Video Projector to include the following: 3 picture tubes, 3 lenses, direct projection system; can be ceiling mounted; capable of 1280 x 1024 pixels or 1500 TV lines; at least 1100 lumens at 10% peak white; horizontal scanning frequency of 15 to 75 kHz; ability to project on fat, curved, or tilted screens; allows input from video and computer sources; remote control with control with control input selection, power on/off, RGB selection, brightness control, sharpness control, hue, picture control, and volume control; includes hardware and operators manual; two year limited warranty on parts and labor; all necessary cables and parts for connection; setup (includes mounting to bracket, connecting to computer, VCR, visual presenter, laserdisc player, and control system, and setting convergence with computer and video sources.)

Slide 35 : 19 / 28 : Immersion


From 3D on a screen to Virtual Reality

Most often we present 3-dimensional graphics on 2-dimensional displays.
What is the potential for presenting 3D information in a way that it can be percieved as 3D?

Virtual Reality = Computer Graphics in Real Time + Immersion + Interaction + other perceptive feedback (touch, sound, smell...)

Terminology by K.-P. Beier
The term 'Virtual Reality' (VR) was initially coined by Jaron Lanier, founder of VPL Research (1989). Other related terms include 'Artificial Reality' (Myron Krueger, 1970s), 'Cyberspace' (William Gibson, 1984), and, more recently, 'Virtual Worlds' and 'Virtual Environments' (1990s).
Today, 'Virtual Reality' is used in a variety of ways and often in a confusing and misleading manner. Originally, the term referred to 'Immersive Virtual Reality.' In immersive VR, the user becomes fully immersed in an artificial, three-dimensional world that is completely generated by a computer.

 Characteristics of Immersive VR

The unique characteristics of immersive virtual reality can be summarized as follows:

HMDs, Caves & Chameleon: A Human-Centric Analysis of Interaction in Virtual Space

Slide 36 : 20 / 28 : Immersion Technology

Immersion Technologies

From simple little flat screen to CAVEs

Computer Screen

Head-Mounted Display (HMD)

BOUM and other

Large Screen, Reality Center




TAN Projection Technology :

Slide 37 : 21 / 28 : Computer Screen

Computer Screen...

spherical one ? ....... Elumens :

Slide 38 : 22 / 28 : Head-Mounted Display (HMD)

Head-Mounted Display (HMD)

UP :

Modern inexpensive HMD: The General Reality CE-200W. (Photo: General Reality Corp.)


The head-mounted display (HMD) was the first device providing its wearer with an immersive experience. Evans and Sutherland demonstrated a head-mounted stereo display already in 1965. The EyePhone from VPL Research was the first commercially available HMD (1989).

A typical HMD houses two miniature display screens and an optical system that channels the images from the screens to the eyes, thereby, presenting a stereo view of a virtual world. A motion tracker continuously measures the position and orientation of the user's head and allows the image generating computer to adjust the scene representation to the current view.

As a result, the viewer can look around and walk through the surrounding virtual environment.

Issues : Heavy

Consider carrying two displays around on your head.
+ Stereopsis is a strong
    3D queue
+ Existing Technology
+ Personal Display
- Obtrusive
- Narrow FOV
    (Tunnel Vision)
- Low Resolution
- Tracking
Currently the most popular 3-Dimensional (VR) display

What is the best way to get steroscopique view of two scenes : it is by giving one differente image to each eyes


To overcome the often uncomfortable intrusiveness of a head-mounted display, alternative concepts (e.g., BOOM and CAVE) for immersive viewing of virtual environments were developed.


Slide 39 : 23 / 28 : BOOM


Fakespace BOOM3C boom mounted display (Photo: Fakespace, Inc.)

The BOOM (Binocular Omni-Orientation Monitor) from Fakespace is a head-coupled stereoscopic display device.

Screens and optical system are housed in a box that is attached to a multi-link arm. The user looks into the box through two holes, sees the virtual world, and can guide the box to any position within the operational volume of the device. Head tracking is accomplished via sensors in the links of the arm that holds the box.

Art+Com virtual car display. A counter-balanced boom constrains the display movement as well as supports its weight. (Photo: Art+Com).  Art+Com VR Control: Note that the display in the previous photo is a touch screen that enables the operator to interact with the image. (Photo: Art+Com).


Slide 40 : 24 / 28 : Large Screen, Reality Center

Large Screen, Reality Center

SGI France

IMMERSIA: salle de projection immersiveEn 1999, l'Irisa a fait l'acquisition d'un équipement de projection immersive, composé d'une station Sgi onyx2 tri-pipes et de trois projecteurs barco 1208S.
La projection est faite sur un écran semi-cylindrique d'un rayon de 3,80m, d'un angle d'ouverture de 135 degrés et d'une hauteur de 2.38m. La projection peut être en stéréovision à 96Hz ou 120Hz pour obtenir une vision en relief.

Slide 41 : 25 / 28 : Workbench


The ImmersaDesk VR System. A large format rear-projection flat stereo display (Photo: Electronic Visualization Laboratory at the University of Illinois at Chicago) 

I3D - INRIA-Rocquencourt
Domaine de Voluceau

Slide 42 : 26 / 28 : Wedge


Slide 43 : 27 / 28 : CAVE (Cave Automatic Virtual Environment)

CAVE (Cave Automatic Virtual Environment)

Schematic of an idealized Cave VR system.

Tiled rear projection stereo images appear on up to six faces of the room in which the operator works. In practice, most Caves have three to four faces with projections. (Image from: Cruz-Neira, Sandin, DeFanti, Kenyon and Hart, 1992). 

The CAVE (Cave Automatic Virtual Environment) was developed at the University of Illinois at Chicago and provides the illusion of immersion by projecting stereo images on the walls and floor of a room-sized cube. Several persons wearing lightweight stereo glasses can enter and walk freely inside the CAVE. A head tracking system continuously adjust the stereo projection to the current position of the leading viewer.



Slide 44 : 28 / 28 : Following issues

Following technical issues

Projector use : projection or transmission ?

issues :

Screen should transmit polarisation

Refreshment rate should be high

More with color and eyes subject

HMDs, Caves & Chameleon: A Human-Centric Analysis of Interaction in Virtual Space