1 - Computer Graphics Background
Sage Air Defence
System (Semi Automatic Ground Environment)
- Built by IBM for the Air Force in the 1950s
- Used computers to track aircraft and displayed
radar blips on computer graphic consoles as interactive vector graphics
- One of the first applications of computer graphics
to track enemy aircraft.
- IBM, Sperry-Rand, Burroughs and a few other
computer companies existed
- Computers had a few kilobytes of memory, no
operating systems to speak of and no graphical display monitors
- Peripherals were Hollerith punch cards, line
printers, and roll-paper plotters.
- Only programming languages supported were
assembler, FORTRAN, and Algol
- Function graphs and ``Snoopy'' calendars were about
the only graphics done.
- 1963 - Ivan Sutherland presented his paper Sketchpad
at the Summer Joint Computer Conference
- Sketchpad allowed interactive design on a vector
graphics display monitor with a light pen input device
- True origins of computer graphics
- Jack Bresenham draws lines on a raster device
- Anti-aliased lines and curve drawing is a
major topic in computer graphics.
- Steve Coons introduced parametric surfaces and
developed early computer aided geometric design concepts.
- Work of Pierre Bézier on parametric curves and
surfaces also became public.
- Author Appel at IBM developed hidden surface and
shadow algorithms that were pre-cursors to ray tracing.
- Doug Englebart invented the mouse at Xerox
- Evans & Sutherland Corporation and General
Electric build flight simulators with real-time raster graphics
- State-of-the-art computer was:
- IBM 360 computer with
about 64 KB of memory
- Tektronix 4014 storage
tube or a vector display
- light pen
Tektronix Display :
- ability to be used as a terminal, linked to a
- 64 Kb RAM
- Resident BASIC Interpreter
- Resident Graphics System (in BASIC)
- Expanded cartridge with signal processing libraries
- Rendering (shading) devised by Gouraud and Phong at
the University of Utah
- Phong also introduced a reflection model that
included specular highlights
- Keyframe-based animation for 3-D graphics was
- Xerox PARC developed a "paint'' program.
- Ed Catmull introduced parametric patch rendering,
the z-buffer algorithm, and texture mapping.
- Evans & Sutherland Picture System:
- high-end graphics computer
- vector display with
hardware support for clipping and perspective
- Xerox PARC introduced the Altos personal computer
- Turned Whitted developed recursive ray
tracing,which became the standard for photorealism
- The Apple I and II computers became the
first commercial successes for personal computing
- DEC VAX computer was the mainframe (mini)
computer of choice.
- Arcade games such as Pong and Pac Mac became
- Laser printers were invented at Xerox PARC.
- Xerox Star Introduced - GUI developed
- IBM PC marketed in 1981
- Apple MacIntosh started production in 1984
- Computers with a mouse, bitmapped (raster) display,
and Ethernet became the standard in academic settings
- Jim Blinn introduces blobby models and
texture mapping concepts.
- Binary space partitioning (BSP) trees
introduced as a data structure
- Loren Carpenter starting exploring fractals
in computer graphics
- Postscript was developed by John Warnock and
Adobe was formed.
- Steve Cook introduced stochastic sampling to
- Character animation became the goal for
- Radiosity introduced by Greenberg at
- Photoshop was marketed by Adobe.
- Video arcade games took of
- Desktop publishing begins.
- Unix with X windows was the platform of
- Sun workstations, with the Motorola 680x0
chipset became popular as advanced workstation
- Video Graphics Array (VGA) card was invented
- Silicon Graphics (SGI) workstations
supported real-time raster line drawing and later polygons became the
computer graphics standard.
- Data glove, a precursor to virtual reality,
was invented at NASA
- VLSI for special purpose graphics processors
and parallel processing became hot research areas.
- SGI workstation with at least 16 MB of
memory a must-have computer:
- 24-bit raster display
- hardware support for
- z-buffering for hidden
- Laser printers and single frame video
recorders were standard.
- Unix, X and Silicon Graphics GL were the
operating systems, window system and application programming interface
- Shaded raster graphics introduced in motion
- Mosaic, the first graphical Internet browser ,
written at the University of Illinois, National Center for Scientific
- MPEG standards for compressed video began to be promulgated.
- Dynamical systems (physically based modeling) that
allowed animation with collisions, gravity, friction, and cause and
effects were introduced.
- In 1992 OpenGL became the standard for graphics
- In 1993,the World Wide Web took off.
- Surface subdivision algorithms were
- Wavelets begin to be used in computer graphics.
- Intel 486 chipset gives PCs reasonable
floating point performance
- 1994 - Silicon Graphics produces the Reality
Engine: hardware for real-time texture mapping
- Ninetendo 64 game consoleprovides Reality
Engine-like graphics for game players.
- Scanners introduced.
- PC market erupts and supercomputers
- SGI collapses and startups entergraphics
- Image based rendering becomes area for
research in photo-realistic graphics
- Linux and open source software become
- PC graphics cards,(e.g. 3dfx and Nvidia),
- Pentium chipset makes PCs almost as powerful as
- Motion capture, begun with the data glove, becomes
a primary method for generating animation sequences.
- 3-D video games become very popular: DOOM (which
uses BSP trees), Quake, Mario Brothers, etc.
- Graphics effects in movies becomes pervasive:
Terminator 2, Jurassic Park, Toy Story, Titanic, Star Wars I. V
- Virtual reality and the Virtual Reality Markup
- Object Model
- Lighting Model
- Camera Model
Wireframe models with
Phong Shading - Polygon
Phong Shading - Bicubic Patches
Focal Lengths and Angles of
Angle of View (Degrees)
Moderate Wide Angle
Unit Cube at 5 units from image plane
Camera held fixed with different angles
(Extreme Wide Angle, Wide Angle, Normal, Telephoto)
Camera position adjusted maintaing
constant image size
(Extreme Wide Angle, Wide Angle, Normal, Telephoto)
Algorithm - Depth Sort
z-buffer (depth buffer)
real world environments receive light in 3 ways:
- Directly from exisiting light sources
such as the sun or a lit candle
- Light that passes and refracts through
transparent objects such as water or a glass vase
- Light reflected, bounced, or diffused
from other exisiting surfaces in the environment
- ambient light
- diffuse light
- specular light
- Phong model
Simple Shading Model
- Objects under the influence of light
- point light
- no interaction
- ad hoc, not
based on model of light propagation
- hardware support
- Light from the light source is sent in
- Object appearance independent of viewer
- Only depends on relative position of
Diffuse + Ambient
Imperfect Reflector - Phong
- From field of thermal engineering
to account for radiative heat transfer
- Foundation - conservation of
radiative energy in a closed environment
- First applied to computer graphics
in 1984 at Cornell and Hiroshima University
- Calculates lighting effects of ideal
- Other rendering techniques use a
directionless " ambient lighting "
- are three-dimensional object space
algorithms that solve for intensities at disrcete points or areas on
modeled surfaces, not for pixels on a 2D image plane.
- create solutions independent of
camera location or orientation.
- make all surfaces capable of
reflecting or emitting light energy
- Radiosity methods compute specular
reflections and refractive transparencies as a second pass using
ray-traced specular reflections and transparencies
1. Modeled world is broken
into a finite number of N discrete patches
2. Radiosity equation used
to relate patches
3. N simultaneous equations
solved iterartively using Gauss-Seidel method
4. The radiosity equation
uses of the following:
Energy that leaves Surface_A and strikes Surface_B is attenuated by 2
- The physical relationship between Surface_A and
Surface_B (known as the form factor).
- The reflectivity of Surface_A (some light will
be absorbed and not reflected to Surface_B).
factors are dimensionless quantities that describe the radiative exchange
between 2 surfaces based on the geometric relationship within their virtual