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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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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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