Computer Graphics

Lecture 1 - Computer Graphics Background

 

History

1950s

Sage Air Defence System  (Semi Automatic Ground Environment)  


1960s

Sketchpad

Software and Algorithms

Hardware and Technology

Early '70's

 
Tektronix Display : 

Software and Algorithms

Hardware and Technology

Mid to Late '70's

Software and Algorithms

Hardware and Technology

Early '80's

Hardware and Technology


 
Xerox Star                                                Apple Lisa

Middle to Late '80's

Software and Algorithms

Hardware and Technology

Early '90's

Software and Algorithms

Hardware and Technology

Middle to Late '90's

Software and Algorithms

Hardware and Technology

Rendering Methods


Wireframe models                                                     Wireframe models with hidden lines

Ambient Illumination                                                                Faceted Shading

Gouraud Shading                                                                    Phong Shading

Phong Shading - Polygon Meshes                                    Phong Shading - Bicubic Patches

Advanced Illumination                                                            Texture Mapping

Bump Mapping                                                                            Reflection Mapping

 

Camera Model

Focal Lengths and Angles of View

35mm Camera

Focal Length(mm)

Angle of View (Degrees)

Extreme Telephoto

800 

3.5

 

400

6.0

 

200

12.5

Moderate Telephoto

135

18.0

 

85 

29.0

 

50 

46.0

Normal 

43 

53.0

Moderate Wide Angle

24 

84.0

Wide Angle

18

94.0

Unit Cube at 5 units from image plane

Camera held fixed with different angles of view
(Extreme Wide Angle, Wide Angle, Normal, Telephoto)


Camera position adjusted maintaing constant image size
(Extreme Wide Angle, Wide Angle, Normal, Telephoto)

 

Hidden Surface


Object Space
    Painter's Algorithm - Depth Sort

Image Space
    z-buffer (depth buffer)

Illumination Model

Surfaces in real world environments receive light in 3 ways:

  1. Directly from exisiting light sources such as the sun or a lit candle
  2. Light that passes and refracts through transparent objects such as water or a glass vase
  3. Light reflected, bounced, or diffused from other exisiting surfaces in the environment

Local (Simple)

Material Models

Simple Shading Model

Ambient Light

Diffuse Reflection


 

Diffuse + Ambient


 

Specular

Perfect Reflector (Mirror)

Imperfect Reflector - Phong Model


 

Global

Ray Tracing


www.povray.org

Radiosity

Radiosity Method



Radiosity methods



One-Pass                                                                 Two-Pass

Radiosity Procedure

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 factors:

5. Form factors are dimensionless quantities that describe the radiative exchange between 2 surfaces based on the geometric relationship within their virtual environment