# DDA Line Drawing Algorithm Solved Example

### Digital Differential Analyzer (DDA) Line Drawing Algorithm Solved Example

There are three popular line drawing algorithms in computer graphics.

1. DDA Line Drawing Algorithm

2. Bresenham Line Drawing Algorithm

3. Mid Point Line Drawing Algorithm

In this tutorial we will disscuss the DDA line algorithm and solve few numarical examples using DDA algorithm.

### DDA Algorithm

Digital Differential Analyzer (DDA) Algorithm is the simplest line drawing algorithm.

Given –

Starting coordinates = (X0, Y0)

Ending coordinates = (Xn, Yn)

A four-step approach is followed to generate the line.

Step 1:

Calculate parameters ΔX, ΔY and M from the given input.

These parameters are calculated as –

ΔX = Xn – X0

ΔY =Yn – Y0

M = ΔY / ΔX

Step 2:

Find the number of steps or points in between the starting and ending coordinates.

if (absolute (ΔX) > absolute (ΔY))

Steps = absolute (ΔX);

else

Steps = absolute (ΔY);

Step 3:

Suppose the current point is (Xp, Yp) and the next point is (Xp+1, Yp+1).

Find the next point by following the below three cases –

Case 1: if (M<1)

Xp+1= Round off (1 + Xp)

Yp+1= Round off (M + Yp)

Case 2: if (M=1)

Xp+1= Round off (1 + Xp)

Yp+1= Round off (1 + Yp)

Case 3: if (M<1)

Xp+1= Round off (1/M + Xp)

Yp+1= Round off (1 + Yp)

Step 4:

Keep repeating Step-03 until the endpoint is reached or the number of generated new points (including the starting and ending points) equals the steps count.