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 BuffersStorage 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 of 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 outputdouble buffering

Depth Buffer or Z-buffer:stores distance values used for hidden surface elimination

Other Buffers:Stencil BufferAccumulation Buffer

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Graphics HardwareImage - 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 algorithmCompletely freeing CPUParallelism

• 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 graphicsRaster image is converted to dotsDifferent shades achieved using halftoning

• Printer technologiesInkjet printersLaser printers

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

Points: a, bVectors: 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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