Introduction to Computer Graphics

Farhana Bandukwala, PhDLecture 1

Outline

• People and logistics• Assignments and grading• Graphics: then and now• Image analysis vs graphics• Applications• Introduction to OpenGL

People and logistics

• Instructor: Farhana Bandukwala, PhD– Office hours M/W after class or by appt. – Contact information: farhana@alumni.carnegiemellon.edu

• TAs: Kuo-Wen Lo, Ninad Dewal– Office hours (TBD)

• Textbooks– Interactive Computer Graphics, by Edward Angel– Open GL Programming Guide by Woo, Neider,Davis and

Shreiner

Assignments and Grading

• Programming assignments worth 250 pts1. Simple Open GL drawing: 25 (+10)2. 2D Curves Rendering: 75 (+15)3. 3D Rendering w/Surfaces & Illumination: 75 (+25)4. Hierarchical Objects & Animation: 75 (+25)

• Midterm exam: worth 75pts• Final exam: worth 75 pts• Syllabus on handout

Catalysts in early 80’s• Raster graphics capable computers

– Xerox Start, Apple MAC, IBM PC• Virtual graphics terminals

– Windows• Direct manipulation

– Point & click

Raster graphics

• Bitmap graphics • Rectangular array of points: pixels• For example: Xerox Star, Mac, IBM PC

Virtual Graphical Terminals

• Windows to organize screen space• Tools: desktop, window manager • Multi-tasking: powerful motivation

Direct Manipulation

• Point-&-Click• Icons and buttons to represent objects and

operators

Graphics vs Image analysis

• Graphics = synthesis – images from model of world

• Image processing = analysis – analysis of picture to build model of the scene

Graphics

Image Analysis/Computer Vision

Applications

• User interfaces: most widespread (research areas include HCI)

Applications: Data visualization

• Scientific, molecular, medical

Applications: Publishing

• Photoshop, Framemaker, Word, Powerpoint!

Applications: CAD

• Auto, Engines, Marketing models

Applications: Entertainment

• Games, Movies, Commercials

OpenGL• Platform independent software API to

graphics hardware– Core Open GL (gl*)

• Allows displaying & transforming models composed of primitives,lights,textures

– OpenGL Utility library (glu*)• High level functions for creating and manipulating

objects– OpenGL Utility Toolkit (glut*)

• Platform independent window management API

Steps to create a picture

1. Construct shapes from primitives using a model of objects

2. Arrange shapes in a “scene”3. Choose a viewing direction 4. Assign attributes (color, texture) to shapes5. Calculate the projection of scene onto display window

Sample OpenGL code#include <GL/glut.h>#include <stdlib.h>

void initViewport(void){glMatrixMode(GL_PROJECTION);glLoadIdentity();glOrtho(0.0,1.0,0.0,1.0,-1.0,1.0);

}

void display(void){// Initialize bufferglClearColor(0.0,0.0,0.0);glClear(GL_COLOR_BUFFER_BIT);

// Initialize attributes (color);glColor3f(1.0,1.0,1.0);

//Draw squareglBegin(GL_POLYGON);glVertex2f(0.25,0.25);glVertex2f(0.25,0.75);glVertex2f(0.75,0.75);glVertex2f(0.75,0.25);glEnd();

//Flush bufferglFlush();

}