Primitive Line Drawing Algorthms

Question 1

What is DDA?

Answer 1

Digital difference analyzer.

Question 2

What is the basic idea of DDA?

Answer 2

To calculate x or y by looking at delta x or delta y sampled at unit intervals.

Question 3

What is Bresenham’s Algorithm?

Answer 3

An algorithm to calculate a line using only integer math.

Question 4

What are the five steps of Bresenham’s Algorithm?

Answer 4

1. Get endpoints, left endpoints (x0, y0)
2. Plot (x0, y0)
3. Calculate constants, dx, dy, 2dy, 2dy-2dx, decision parameter p0 = 2dy-dx.
4. fpr each x if p < 0 go east and p = p + 2dy if p > 0 go northeast and p = p + 2dy - 2dx.
5. Repeat 4 until done.