DDA Algorithm in Computer Graphics

Step1: Start Algorithm

Step2: Declare x1,y1,x2,y2,dx,dy,x,y as integer variables.

Step3: Enter value of x1,y1,x2,y2.

Step4: Calculate dx = x2-x1

Step5: Calculate dy = y2-y1

Step 6: If ABS (dx) > ABS (dy)

Then step = abs (dx)       Else

Step 7: xinc=dx/step

yinc=dy/step assign x = x1 assign y = y1

Step 8: Set pixel (x, y)

Step 9: x = x + xinc

y = y + yinc

Set pixels (Round (x), Round (y))

Step 10: Repeat step 9 until x = x2

Step 11: End Algorithm

Example Questions:

If a line is drawn from (2, 3) to (6, 15) with use of DDA. How many points will needed to generate such line?

Solution:

P1 (2,3)        P11 (6,15) x1=2

y1=3 x2= 6 y2=15

dx = 6 - 2 = 4

dy = 15 - 3 = 12

m = dy/dx = 12/4 = 3

For calculating next value of x takes

x = x + 1/m