CSE 410 Computer Graphics Sessional

INTRODUCTION

What is COMPUTER GRAPHICS?

Painting with numbers!

Aspects

• Modeling• Rendering• Animation

Aspects

VisualizationVirtual RealityImage ProcessingUser interaction / Human Computer Interface3D Scanning

Applicability?

Extent of CGWhat are we going to learn?

Extent of CG

How CG systems work.How to model of real life objects.How to render modeled objects.How to make things more realistic.How to make things more beautiful.

Extent of CSE410

Extent of CSE410

Understanding of Graphics API : OpenGLUnderstand how to use 3D API’s to create

games, animations, renders or visualization.Learn how API’s work from inside.

CG Basics

Representation

Points

Lines

Polygon

Mesh

Textures , shaders , post processing and other techniques like radiocity and raytracing are used to produce realistic rendering of modeled objects.

RenderingHow can we show the objects on the screen from the

mathematical data of the models we have?

2D Hypothetical World

A canvasInfinitely extended drawing area having two perpendicular axes ( x and y )

A viewporta finite 2d rectangular are ( lets say it is 8x6 pixels ) that represents what is shown on the screen.

Lets assume we have the following things true for our fantasy world of rendering.

CANVASVIEWPORT

We can do following drawing on the canvas.drawPointdrawRectangle (width , height )drawPicture

And the following commands to place our desired drawing on the desired part of the canvas.

Translate ( x , y )Rotate ( x )

These commands effects any drawing done after calling them.

Sample drawings and outputspoint().

Sample drawings and outputstranslate(3,2)drawPoint().

Now lets say we want to draw the following picture.

Translate ( -10 , -5)Rotate ( -45 )drawRectangle ( 10 , 5 )

…and also don’t forget the need of a camera.

Camera (-4,-3)

Now.. how does our graphics card calculate where

to draw the pixels when it receives such coordinates for drawing from our program?

Sample again…

camera ( 0 , 0 )translate ( 3,-1)

point()

Canvas coordinate (3,-1)Screen coordinate (3,1)

Sample again…

camera ( -2 , 1 )translate ( 3,-1)

point()

Canvas coordinate (3,-1)Screen coordinate ?

( 5 , 2 )

x = 0 + 3 – (-2) = 5y = 0 – (-1) + 1 = 2

point()

translate ( 3,-1)

camera ( -2 , 1 )

Calculation for x axisCommands

0 + 3

- ( -2)

Now we can make an equation !

Final coordinate on the screen

=

Actual coordinate+Transformation-Camera Position

}Gives us coordinate on the canvas

}Gives us coordinate on the screen

Modeling Transformation

Viewing Transformation

This process of calculating final output picture from initial coordinates/models in a step by step manner is known as

Graphics Pipeline

With understanding of the hypothetical world now lets get real,

How does our actual graphics systems work?How 3D objects are rendered on the screen?What more is there in the 3D pipeline?

Lets explore!