Lighting
-emission
-ambient - light scattered from environment - comes from all directions
-diffuse - light scattered in all directions when hits a surface
-specular - shiny light reflected in one direction from a surface
object = (ambient+diffuse+specula

Midpoint algorithm (Bresenham)
y=dy/dx x + b /slope intercept
O=dy x - dx y + c = Ax + By + C
F(x,y) = dy x - dx y + c
F(x+1,y+1/2) = dy(x+1) - dy(y+1/2) + c
midpoint: deltaF = F(x+1,y+1/2) - F(x,y) = dy - 1/2dx => 2dy-dx
deltaNE = F(x+1,y+1) - F(x - y) =