1. The D Algorithm 
If 1 does not fit within the triangle the angle is chosen along the steepest edge or diagonal resulting in a slope and direction equivalent to D8

2. Example 49 48 47 55 67 52 45 42 56 48 49 42 56 1 47 45 56 42 45 55 67 52 11 3
15o
11.4

3. Example 49 48 47 55 67 52 45 42 56 48 49 42 56 42 49 2 56 47 45 55 67 52 7
45o
9.9

4. Example 49 48 47 55 67 52 45 42 56 48 49 42 3 56 49 48 56 47 45 3 55 67 52 1 7
8.1o
7.1
98.1o

5. Example 49 48 47 55 67 52 45 42 56 48 49 42 4 56 47 45 4 55 67 52 48
180o
Pick Slope Along Edge 9 1 47 56

6. Example 49 48 47 55 67 52 45 42 56 48 49 42 56 47 45 5 5 55 67 52
180o
Pick Slope Along Edge 8 47 9 56 55

7. Example 49 48 47 55 67 52 45 42 56 48 49 42 56 47 45 6 6 55 67 52
225o 11 12 56
Pick Slope Along Edge 55 67

8. Example 49 48 47 55 67 52 45 42 56 48 49 42 56 47 45 7 55 67 52 7
315o 11 56 15
Pick Slope Along Edge 67 52

9. Example 49 48 47 55 67 52 45 42 56 48 49 42 56 47 45 8 55 67 52 8 0o 7 45 56 11
Pick Slope Along Edge 52

10. Example 45 42 49 48 47 55 67 52 56 49 48 47 55 67 52 45 42 56