COMPUTER GRAPHICS

                                                          (COMPUTER GRAPHICS)

                          DDA   ALGORITHM     

                                                                                          

                    

       BASIC

       -  The full form of the DDA algorithm is the Digital Differential analyzer algorithm.

            

            we know that equation of the line is y = mx + c,  where m is the slope of the line.

          

          different type of equation of line     1.  y-y1 = m (x-x1)/(x2-x1)  , where m = y2-y1/x2-x1

                                                                    2. x/a + y/b =1  where  y intercept is b 

                                                                                                          x intercept is a

         - In DDA algorithm we have to print the line in the graphic console.

              

          Explanation : 

                 let two coordinate of given line is (x1,y1)  and (x2,y2)

                   1.   calculate dx  = x2-x1  and dy = y2-y1

                   2.   calculate the maximum between mod ( |-2| = 2 or |3| = 3 ) of dx and dy. and store max value in steps.

                    

                  3.  take a variable Xincr = dx/steps  and Yincr= dy/steps.

                  4  last increase the  x1 and y1 on adding Xincr and Yincr and put pixel in any color.

                          x1 = x1 +Xincr

                           y1  = y1 + Yincr

              note  Xk+1= Xk + 1;   Yk+1 = Yk +1

       Code  in C++

                

             #include<iostream>

             #include<graphics.h>

            #include<conio.h>

             using namespace std;

void DDA(int x1,int y1,int x2, int y2)

{

int dx=x2-x1,dy=y2-y1;

int step;

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

{

step=abs(dx);

}

else

{

   step=abs(dy);

}

float m=dy/dx;

float Xincr=dx/step;

float Yincr=dy/step;

for(int i =0;i<=step;i++)

{

putpixel(x1,y1,WHITE);

x1=x1+Xincr;

y1=y1+Yincr;

                   delay(100);

}

}

int main()

{

int gd=DETECT,gm;

initgraph(&gd,&gm,"");

 int x1,y1,x2,y2;

 cin>>x1>>y1>>x2>>y2;

 

    DDA(x1, x2, x2, y2); 

getch();

return 0;

}   

The drawback of the DDA algorithm

1. It takes a long time.

2. It has less accuracy.

Thanks