Lecture computer graphics and virtual reality slides lesson 2 graphics systems

Trang 5 Modeling■ Describing to the computer□What is a table, a car…□Concerned with: Trang 6 Rendering■ Draw the description□Create 2D image from 2D / 3D models□Concerned with:▫viewing

Lesson 2

Graphics systems

Trinh Thanh Trung School of ICT, HUST

1 Graphics pipeline

2 Graphics software

3 Graphics hardware

Graphics pipeline

Object representation

■ To display an object to the screen…

Displaying Rendering

Modeling

■ Describing (to the computer)

□ What is a table, a car…

□ Concerned with:

▫ geometric info, color models, material property, lighting property

■ Draw the description

□ Create 2D image from 2D / 3D models

□ Concerned with:

▫ viewing & projection

▫ drawing & clipping primitives

▫ local illumination & shading

▫ texture mapping, global rendering

Application stage

■ Entirely done in software by the CPU

■ Load Data: world geometry, user’s input

■ In response to the user’s input, the application stage change the view or scene

Geometry stage

■ Applying transformations to the object vertices (scaling, rotating, translating)

■ View transformation (viewing from the camera)

■ Illumination and shading

Rasterization stage

■ Converting the continuous representation

(curves and lines) into the discrete representation (pixels)

Example scene

1 Modeling objects

• Define polygons, parametric

curves/surfaces, etc & its own coordinate system

2 Model transformation

• Applying translation, scaling and

rotation

3 Perspective projection

• Convert from 3D coordinates to

2D coordinates

4 Hidden surface removal

• Objects occluded by other objects

must not be drawn

5 Shading and lighting

• Define the colour of each pixel

6 Rasterization

• Convert vertex information

into pixel information

• Anti-aliasing

7 Texture mapping

• Map textures on objects

8 Others

• Bump-mapping

• Reflections

• Shadows

Graphics hardware

Graphics hardware overview

Graphics hardware components

■ System Memory: consists of programs and

instructions being executed

■ Graphics Package: provides graphics functions for applications

■ Application Program

■ Frame buffer

■ Video Controller: control display device, convert digital data from framebuffer to pixel on screen

Graphical Processing Unit

■ An extremely flexible and powerful processor

▫ Only designed for and driven by video games

▫ Underlying architectures are rapidly evolving and largely secret

Role in graphics pipeline

■ The role of GPU in graphics pipeline

□ Pipe widths vary

□ Many caches, FIFOs, and so on not shown

■ In modern graphics pipeline

□ Add vertex processor and fragment processor

GPU CPU

Application Transform Rasterizer Shade MemoryVideo

(Textures)

Vertices (3D) Xformed, Lit Vertices

(2D)

Fragments (pre-pixels)

Final pixels (Color, Depth )

Graphics State

Render-to-texture

■ Drives video display from a memory buffer

containing a complete frame of data

□ E.g 24 bits per pixel = 8 bits red , 8 bits green , 8 bits

blue

■ True-color (24-bit) framebuffer stores one byte for red, green or blue

□ Each pixel can have 2 24 colours

□ X : 0  Xmax 2 colour / 1 bit

□ Y : 0  Ymax 16 colour / 4 bit

Graphics display

SONY Trinitron CRT

NEC Hybrid Mask Hitachi EDP Standard Dot-trio

CRT display

■ Raster Displays (early 70s)

□ like television, scan all pixels in regular pattern

□ use frame buffer (video RAM) to eliminate sync problems

▫ RAM ¼ MB (256 KB) cost $2 million in 1971

Pros and cons of CRT

□Discreet sampling (pixels)

□Practical limit on size (call it 40 inches)

□Bulky

□Finicky (convergence, warp, etc.)

Pros and cons of LCD

□Completely flat screen

□Crisp pictures - digital

and uniform colors

Plasma display

■ Plasma display

□ Similar in principle to fluorescent light tubes

□ Small gas-filled capsules are excited by electric field, emits UV light

□ UV excites phosphor Phosphor relaxes, emits some other color

Pros and cons of Plasma

Pros

□Large viewing angle

□Good for large-format

□Phosphors gradually deplete

□Less bright than CRTs, using more power

■ Organic Light-Emitting Diode (OLED) Arrays

□ OLEDs function like regular semiconductor LEDs, but with thin-film polymer construction

▫ Thin-film deposition of organic, light-emitting molecules through vapor sublimation in a vacuum.

▫ Dope emissive layers with fluorescent molecules to create color.

▫ Not grown like a crystal, no high-temperature doping

▫ Thus, easier to create large-area OLEDs

Pros and cons of OLED

□Prone to water damage

Graphics software

Input and

output devices Metafiles

Operating system

Graphics software

■ Interface between application software and

graphics hardware system

■ Consists of input subroutines and output

subroutines accepting input data or commands

from a user and converting internal representations into external pictures on screen, respectively

Graphics official standards

■ GKS (Graphics Kernel System)

■ GKS Functional Description, ANSI X3.124 - 1985

■ GKS - 3D Functional Description, ISO Doc

#8805:1988

■ CGI (Computer Graphics Interface System)

■ CGM (Computer Graphics Metafile)

■ VRML (Virtual Reality Modeling Language)

■ PHIGS (Programmers Hierarchical Interactive Graphics Standard)

□ PHIGS Functional Description, ANSI X3.144 - 1985.

□ PHIGS+ Functional Description, 1988, 1992

Unofficial

Any questions?

Lecture notes provided by School of Information and

Communication Technology, Hanoi University of Science and

Technology.

Composed by Huynh Quyet Thang, Le Tan Hung, Trinh Thanh

Trung and others

Edited by Trinh Thanh Trung

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