Introduction Graphics & Visualization: Principles & - - PowerPoint PPT Presentation

Graphics & Visualization

Chapter 1

Introduction

Graphics & Visualization: Principles & Algorithms

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• Milestones in the history of computer graphics:

Brief History

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• CPU Vs GPU

Brief History (2)

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Applications

• Special effects for films and advertisements
• Scientific exploration through visualization
• Interactive simulation
• Computer games
• Computer-aided geometric design and solid modeling (CAGD)
• Graphical user interfaces (GUIs)
• Computer art

Concepts

• 3D or 2D scenes are composed of primitives (e.g. points, lines,

curves, polygons, mathematical solids or functions)

• A raster image is a 2D array of pixels
• Computer Graphics use principles and algorithms to generate from

a scene, a raster image that can be depicted on a display device

• Scene Computer Graphics

Raster Image

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Concepts (2)

• Rasterization steps for a two-dimensional document

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Concepts (3)

• Visualization exploits visual presentation of large data sets to

increase understanding

• The result of visualization is a visualization object
• Modeling encompasses techniques for the representation of

graphical objects

• Data Set

Visualization Model

• Graphics Pipeline is a sequence of stages that create a digital

image out of a model

• Model

Graphics Pipeline Image

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Graphics Pipeline

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Graphics Pipeline (2)

• Operations on primitives in the standard direct rendering

graphics pipeline :

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Graphics Pipeline (3)

• For the above example:

(a) Geometry transformation to a common reference frame and view frustum culling. (b) Primitives after viewing transformation, projection, and backface culling. (c) Rasterization (d) fragment depth sorting: the darker a shade, the nearer the corresponding point is to the virtual camera. (e) Material color estimation. (f) Shading and other fragment operations (such as fog).

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Image Buffers

Storage and Encoding of Digital Images :

• Image buffer is a 2D array of dimensions w x h
• Size of the image buffer is at least (w x h x bpp) / 8 bytes
• Color depth (bpp) : # bits used to store the color of each pixel
• Color representations:

Monochromatic (grayscale) Multi-channel (red/green/blue) Palleted (CLUT)

• True-color: image buffer stores full color intensity information
• f each pixel
• Color look – up table (CLUT):

bits per pixel do not affect the accuracy of the displayed color

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True-color

Image Buffers (2)

• Image buffer with CLUT:
• Image buffers occupy contiguous space of memory

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Image Buffers (3)

Frame Buffer:

memory where all pixel color information from rasterization

is accumulated before being driven to the graphics output

double buffering

Depth Buffer or Z-buffer:

stores distance values used for hidden surface elimination

Other Buffers:

Stencil Buffer Accumulation Buffer Graphics & Visualization: Principles & Algorithms Chapter 1 13

Graphics Hardware

Image - Generation hardware:

• Display adapters
• Double Buffering:

2 frame buffers, buffer swapping

• 2D graphics accelerators:

Apply 2D rasterization algorithms Partially freeing CPU

• 3D graphics accelerators:

Adoption of Z-buffer algorithm Completely freeing CPU Parallelism

• Programmable graphics hardware

2 types of shaders (vertex, fragment)

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Graphics Hardware (2)

Image - Output hardware:

• Display monitors

Cathode ray tube (CRT) Liquid crystal displays (LCD) Thin – film transistor (TFT)

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Graphics Hardware (3)

• Projection systems

2 projection methods (rear, front) 3 projection technologies (CRT, LCD, DLP)

• Printer graphics

Raster image is converted to dots Different shades achieved using halftoning

• Printer technologies

Inkjet printers Laser printers Graphics & Visualization: Principles & Algorithms Chapter 1 16

Conventions

• Scalars : x, y, z
• Vector quantities :

Points: a, b Vectors: Unit vectors:

• Matrices: M, Rx

Column vectors:

• Functions:

Standard mathematical functions and custom functions: sin(θ) Functions follow the above conventions for scalar and vector quantities

• Norms:
• Standard sets :
• Algorithm descriptions are given in pseudocode based on standard C and C++
• Advanced sections are marked with an asterisk

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