DDA stands for **Digital Differential Analyzer**. It is an incremental method of scan conversion of line. In this method calculation is performed at each step but by using results of previous steps. Digital Differential Analyzer algorithm is the simple line generation algorithm which is explained step by step here. Suppose at step i, the pixels is **(xi,yi)**

**The line of equation for step i**

** yi = mxi+b **....................................... equation 1

Next value will be

** yi+1=mxi+1+b ** .............. equation 2

m = ∆y / ∆x

yi+1-yi=∆y ................... equation 3

yi+1-xi=∆x ................... equation 4

yi+1 = yi+∆y

∆y = m∆x

yi+1 = yi + m∆x

∆x = ∆y/m

xi+1 = xi+∆x

xi+1 = xi+∆y/m

**Case1: **When |m|<1 then (assume that x1<x2)

x = x1, y = y1 set ∆x = 1

yi+1 = y1+m, x = x+1

Until x = x2

**Case2: **When |m|>1 then (assume that y1<y2) x= x1,y=y1 set ∆y=1

xi+1=m , y = y+1

Until y → y2

## Advantage of DDA Line Algorithm

- It is a faster method than method of using direct use of line
- This method does not use multiplication
- It allows us to detect the change in the value of x and y ,so plotting of same point twice is not
- This method gives overflow indication when a point is
- It is an easy method because each step involves just two

## Disadvantage of DDA Line Algorithm

- It involves floating point additions rounding off is Accumulations of round off error cause accumulation of error.
- Rounding off operations and floating point operations consumes a lot of
- It is more suitable for generating line using the But it is less suited for hardware implementation.