Primitive Circle Drawing Algorithms

Question 1

Whats the biggest problem drawing with scan lines?

Answer 1

as the change in y beats the change in x y pixels no not get marked leaving a messed up circle.

Question 2

What is the circle midpoint algorithm?

Answer 2

1. Input radius and center point. Let (x0, y0) = (x, r).
2. Calculate initial decision parameter. p = 5/4 - r.
3. If p < 0 go East, p = p + 2x + 3 else if p >= 0 go SE, p = p + 2x - 2y + 5
4. Determine points of symmetry.
5. Shift point from origin to circle center.