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Computer Graphics

Line Drawing Functions

Point structure

Asima Latif

19-Nov-2009


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12/25/2010 2

Main Mile stones that we will cover in this course

Basic Concepts

Basic Shapes, Line Drawing Algorithms

Projection / Display of Graphics

Transformation

Parametric Equations

Graphics Pipeline OpenGL

Two dimensional Graphics

3D Graphics


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Book / Other Material

Computer Graphics FS Hill or the hevern one

Turbo C++ remember that there is a BGI

folder

Visual C++ , OpenGL GLUT Library

Java3D optional


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Origin Center of the screen

To get the center of the screen

We have two functions

Getmaxx()

Getmaxy()

Center of Screen

Int cx = getmaxx()/2;

Int cy = getmaxy()/2;


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Complete Program with cx, cy

int main(void)

{

int gdriver = DETECT, gmode;

initgraph(&gdriver, &gmode, "\\tc\\bgi");int radius=100;

Int cx=getmaxx()/2;

Int cy=getmaxy()/2;

circle(cx, cy, radius);

getch();

closegraph();

}


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Drawing Lines .. 1

Line(int x1,int y1,int x2, int y2);

Draws a line between (x1,y1) AND (x2,y2)

int main(void)

{


initgraph(&gdriver, &gmode, "\\tc\\bgi");

Line(cx,cy,cx+200,cy);

getch();

closegraph();

}


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Drawing Lines .. 1

int main(void)

{


initgraph(&gdriver, &gmode, "\\tc\\bgi");

Line(cx,cy,cx+200,cy);

Line(cx,cy,cx,cy-200);

getch();

closegraph();

}


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Drawing Line 2

Linerel(int dx, int dy)

Draws a line from the current position to the

distance dx, and dy

Curret Position CP is achived through using

the function moveto(int x, int y);


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Drawing Lines .. 2

int main(void)

{


initgraph(&gdriver, &gmode, "\\tc\\bgi");Moveto(cx,cy);

Linerel(200,0);

getch();

closegraph();

}


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Drawing Lines .. 3

Lineto(int x, int y)

Draws a line from the current position to the

given point.


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Drawing Lines .. 3

int main(void)

{


initgraph(&gdriver, &gmode, "\\tc\\bgi");Moveto(cx,cy);

Lineto(100,200);

getch();

closegraph();

}


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Line Drawing AlgorithmDigital Differential Analyzer


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DDAvoid lineDDA(int xa,int ya,int xb,int yb)

{

int dx,dy,steps;dx=xb-xa;

dy=yb-ya;

float xincrement,yincrement,x,y;

if (abs(dx)>abs(dy))

steps=abs(dx);

elsesteps=abs(dy);

xincrement=dx/steps;

yincrement=dy/steps;

x=xa,y=ya;

putpixel(round(x),round(y),2);

for (int k=1;k


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Main function

void main()

{

int driver=DETECT,mode;

initgraph(&driver,&mode,"C:\\tc\\bgi");

lineDDA(100,100,401,401);

getch();

closegraph();

}


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LINE MIDPOINT

ALGORITHM(BRESHMAN ALGORITHM

void main()

{

int gd=DETECT,gm,x0,y0,x1,y1,dx,dy,d,x,y,c1,c2;

initgraph(&gd,&gm,"c:\\tc\\bgi");

clrscr();

couty0;

coutx1>>y1;

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dx=x1-x0;

dy=y1-y0;

d=2*dy-dx;

c1=2*dy;c2=2*(dy-dx);

if(x1>x0)

{

x=x0; y=y0;

putpixel(x,y,RED);

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while(x


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else

{

x=x0; y=y0;putpixel(x,y,YELLOW);

while(x>=x1)

{

if(d


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Translation

void main()

{

int

gd=DETECT,gm,x[1

0],y[10],a,b,i,j,dx,dy;

clrscr();

initgraph(&gd,&gm,"c:\\tc\\bgi");

cout>j;

cout>y[i];

setcolor(BLUE);

for(i=1;i


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Translation

line(x[i],y[i],x[0],y[0

]);

cout>dx>>dy;

cout


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Thats all for Today

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