Chapter 2

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# Chapter 2 - PowerPoint PPT Presentation

Chapter 2 Graphics Programming 24 Jan 20067 Sierpinski Gasket pre-Mandelbrot classic found by W. Sierpinski around World War I. generated by recursivly dividing a triangle into four congruent smaller triangles think of the interior triangles as "holes”

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## Chapter 2

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Chapter 2
• Graphics Programming
• 24 Jan 20067
• pre-Mandelbrot classic
• found by W. Sierpinski around World War I.
• generated by recursivly dividing a triangle into four congruent smaller triangles
• think of the interior triangles as "holes”
• they occupy more and more of the total area, while the "solid" portion becomes as hopelessly fragile
Pseudocode

1. Pick a point at random inside the triangle

2. Select one of the three vertices at random

3. Find a point halfway between the initial point and the randomly selected vertex

4. Display this new point by putting some sort of marker, such as a small circle, at its location

5. Replace the initial point with this new point

Pen Plotter
• moveto(x,y)
• lineto(x,y)
Problems with Pen-Plotter model
• 3D difficult
• must convert 3d world to 2d projection explicitly
• OpenGL allows us to focus on building 3D world and let computer handle projections
Display funtion

Check programs online - lectures/chapter1/lab, boat

Coordinate System

3D COORDINATE SYSTEMS

Y

Y

Z

X

X

LEFT HANDED

RIGHT HANDED

Z

Coordinate System in OpenGL
• What units are x, y, and z?
• device independent
• world coordinate system
• Before displaying on output device, world coordinates must be converted to device or raster or screen coordinates
POINT TO REMEMBER
• We are studying computer graphics
• We are not studying OpenGL
• won’t cover all functions in OpenGL
Graphics System as a Black Box

Function Calls

Output

User

Program

Graphics

System

Input/Output

Devices

Data

Input

API Functions
• Primitive Functions
• Attribute Functions
• Viewing Functions
• Transformation Functions
• Input Functions
• Control Functions
OpenGL - What is it?
• A graphics rendering library
• API to produce high-quality, color images from geometric and raster primitives
• Window System and Operating System independent
• OpenGL “doesn’t do windows”
OpenGL
• Most widely adopted graphics standard
• Introduced in 1992
• High visual quality and performance
• Industry standard
• Stable
• Reliable and portable
• Evolving
• Scalable.
• Easy to use.
• Well-documented.
Related APIs
• GLU (OpenGL Utility Library)
• guaranteed to be available
• tesselators
• NURBs, etc.
• some surprisingly common operations, such as projection transformations (such as gluPerspective)
Related APIs
• GLX or WGL
• bridge between window system and OpenGL
• GLUT
• portable bridge between window system and OpenGL
• not “standard”, but uniformly popular
Homework
• Read Chapter 3
• Assignment 2 - Program due 01/31/2007
• Display your scene in 3D. Use at least 5 different graphics primitives.
glOrtho (GLdouble left, GLdouble right, GLdouble, bottom, GLdouble top, GLdouble near, GLdouble far)
• Creates a viewing volume with a box shape.
• Direction of projection is parallel to z axis.
• Viewpoint faces -z axis.
• glOrtho (0.0, (GLdouble) w, 0.0, (GLdouble) h, -500.0, 500.0);