1. Chapter 10 Computer Graphics
Computer Graphics is the study of how to use computers to produce and manipulate visual (digital) data.
Topics include:
Understanding and manipulating “real” images
Photographs, ads
Creating and producing series of images
Animation, movies
Video games
Outputting images
Graphical output, such as graphs and charts
GUIs
Computer Graphics

2. Creation and processing of 2D images
Creation (of 2D graphics)
Converts shapes into patterns of pixels
Image processing
Analyzes images for patterns of pixels for enhancement, changes, etc.
ex: Microsoft’s Paint for
producing 2-dimensional images
ex: Photoshop for eliminating red eye
Computer Graphics

3. Three dimensional images
3D graphics
Must first “create” three-dimensional images
“photograph” the virtual world that is created
Produce the image through large computational process
Convert 3D “photograph” into 2-D image
Research is ongoing for 3-dimensional graphics projector, 3-D GUI
Image processing
Enhancement, perhaps using A.I.
Computer Graphics

4. 3 steps in producing a 3D image
Modeling
Constructing/ building a scene from graphic data and algorithms
Rendering
Converting 3D scene to 2D representation
Perspective projection
Image window defines boundary of final image
Displaying
Converting to pixels, storing in frame buffer, display using graphics cards, typically real-time
Computer Graphics

5. Modeling
Lower or higher quality images depending on their use (foreground objects, for example, need high quality)
Consider higher quality .jpg file depending on number of pixels used (resolution)
Higher quality objects require longer rendering process
Note: we do not convert to pixels until the very end, because pixels are not upwardly scalable
Computer Graphics

6. Modeling
Describe each object as a set of small connecting planar (2D) patches or polygons
These polygons form a polygonal mesh to approximate the object
Using more (smaller) polygons gives higher resolution
Represent each polygon by an equation, perhaps a quadratic equation, if possible
Or build physical model and digitize it by using a pen device to record points on the model
Or, if too complex for either of the above (i.e., actual trees), write program to generate shape
Computer Graphics

7. Rendering Light-Surface Interaction
How light is reflected off an opaque surface
Depends on nature of surface
Light rays reflected over smooth surfaces (specular light) provide bright highlights
Light rays, scattered (diffused) as they ricochet over jagged surfaces, are close to actual color
Surfaces that are not exposed to direct light may be illuminated by scattered reflected rays
Ambient light may result in uniform or mostly dark areas
Computer Graphics

8. Light-Surface interaction
Refraction with a transparent surface
Light rays pass through the object
Rays are bent (refracted) depending on refractive index of material
Rendering software must know
Refractive indexes of material
Which side of object is inside or outside
Is light entering or leaving the object
Computer Graphics

9. Rendering Pipeline
Clipping – picking those 3-D objects that you want from “view volume”
Scan conversion or rasterization
Vector graphics into pixels
Projecting the clippings patched into pixel positions
Hidden-surface removal
Eliminating “background” surfaces
Shading to make the 2-D rendering look like 3-D
Computer Graphics

10. Graphics hardware Graphics cards or adapters attached to bus
Accomplishes the steps in rendering pipeline
Other devices
see
Computer Graphics

11. GPUs and graphics hardware
Multiple cores
Accelerated Graphics Port or PCI-X
Bus PCI -X
Clock 66MHz MHz
Number of bits 64
Data per Clock Cycle 1, 2, 4
Maximum Transfer Rate 533MB/s to 4266MB/s
Bus AGP (accelerated graphics port)
Clock 66MHz
Number of bits 32/ 64
Data per Clock Cycle 1-8
Maximum Transfer Rate 266MB/s- 2133MB/s to4266MB/s
Computer Graphics