2D Scan-line Conversion

1. 2D Scan-line Conversion University of Missouri at Columbia

2. 2D Scan-line Conversion • DDA algorithm • Bresenham’s algorithm

3. DDA algorithm • The simplest algorithm. • Named after Digital Differential Analyzer. (x1, y1) dy (x0, y0) dx

4. DDA Algorithm

5. DDA Algorithm

6. DDA Algorithm

7. DDA Algorithm

8. DDA Algorithm

9. DDA Algorithm

10. 2D Scan-line Conversion • DDA algorithm • Bresenham’s algorithm

11. Bresenham’s Midpoint Algorithm • DDA is simple, efficient, but needs floating points. • Bresenham’s use integer addition only. (x1, y1) dy (x0, y0) dx

12. Bresenham’s Midpoint Algorithm • To choose from the two pixels NE or E depending on the relative position of the midpoint Mand the line. • Choose E if M is above the line, • Choose NE if M is below the line. NE M E (x0, y0)

13. Bresenham’s Midpoint Algorithm • Choose NE if d is positive, • Choose E if d is negative. NE M E (x0, y0)

14. Bresenham’s Midpoint Algorithm • Choose NE if d is positive, • Choose E if d is negative. NE M E (x0, y0)

15. Incremental Calculation of the decision variable dnew NE M E (x0, y0)

16. Bresenham’s Midpoint Algorithm NE M E (x0, y0)