CSC 307 1.0 Graphics Programming · OpenGL • Standard specification defining a cross-language,...

CSC 307 1.0

Graphics Programming

Budditha Hettige

Department of Statistics and Computer Science

Graphics Programming

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Common Uses for Computer

Graphics

• Applications for real-time 3D graphics range from

interactive games and simulations to data visualization

for scientific, medical, or business uses

– Military flight simulators

– Computer-aided design (CAD)

– Architectural or civil planning

– Scientific visualization

– Entertainment

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Movies

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Games

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Simulation

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CAD-CAM & Design

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Architecture

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Virtual Reality

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Visualization

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Medical Imaging

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Graphics System

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User Program User Program IO Devices IO Devices

Graphics API

Graphics System

Graphics System

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Graphics Designing

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Graphics: Conceptual Model

Real Object

Real Object

Human Eye

Human Eye

Display Device

Graphics System

Synthetic Model

Synthetic Camera

Real Light

Synthetic Light Source

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OpenGL

• Standard specification defining a cross-language, cross-

platform API

• Is not a programming language

• Writing applications that produce 2D and 3D computer

graphics

• A software interface to graphics hardware

• Designed and optimized for the display and

manipulation of 3D graphics

• Developed by Silicon Graphics Inc. (SGI) in 1992

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OpenGL-Graphics rendering API

• Rendering API

– High-quality color images composed of geometric

and image primitives

– Window system independent

– Operating system independent

• OpenGL Pipeline

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OpenGL Architecture

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Display List

Polynomial Evaluator

Per Vertex Operations & Primitive Assembly

Rasterization Per Fragment Operations

Frame Buffer

Texture Memory

CPU

Pixel Operations

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Software & Hardware Interfaces

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Software Interface Hardware Interface

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OpenGL and Related APIs

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GLUT

GLU

GL

GLX, AGL or WGL

X, Win32, Mac O/S

software and/or hardware

application program

OpenGL Motif widget or similar

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Related APIs

• AGL, GLX, WGL – glue between OpenGL and windowing systems

• GLU (OpenGL Utility Library) – part of OpenGL

– NURBS, tessellators, quadric shapes, etc.

• GLUT (OpenGL Utility Toolkit) – portable windowing API

– not officially part of OpenGL

• Initial header inclusions (for Windows) – #include<windows.h>

– #include<gl/gl.h>

– #include<gl/glu.h>

– #include <GL/glut.h>

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Function-Naming Conventions

• All OpenGL functions take the following

format <Library prefix><Root command><Optional argument

count><Optional argument type>

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OpenGL data types

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2D Coordinates

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Coordinate Clipping

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Viewports • Mapping Drawing Coordinates to Window

Coordinates

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viewport defined as twice the size of the clipping area

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Viewports

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viewport that matches the clipping area

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OpenGL 3-D coordinates

• Right-handed system

• From point of view of camera looking out into scene:

+X right, -X left

+Y up, -Y down

+Z behind camera, -Z in front

• Positive rotations are counterclockwise around axis of rotation

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OpenGL Geometric Primitives

GL_QUAD_STRIP

GL_POLYGON

GL_TRIANGLE_STRIP

GL_TRIANGLE_FAN

GL_POINTS GL_LINES

GL_LINE_LOOP GL_LINE_STRIP

GL_TRIANGLES

GL_QUADS

Primitives are one- or two-dimensional entities or surfaces such as points, lines, and polygons

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The Vertex—A Position in Space

• Each corner of the any primitive is called a

vertex. Ex: three-dimensional cube consists of

six two dimensional squares, each placed on a

separate face

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Projections: Getting 3D to 2D

• Orthographic Projections

• Perspective Projections

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RGB Color Space

Green (1,0,0)

Blue (0,0,1)

Red (1,0,0)

Yellow (1,1,0)

Magenta (1,0,1)

Blk

Cyan (0,1,1)

White (1,1,1)

G

B

R

Image: Pixel maps to color

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Common Composite Colors

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