When I drew a hex map in a vector fashion (many years ago) I used pointy-side-up hexes, and drew the horizontal zig-zag lines left-to-right across the screen, a

When I drew a hex map in a vector fashion (many years ago) I used pointy-side-up hexes, and drew the horizontal zig-zag lines left-to-right across the screen, and then went back and filled in the vertical lines. This ensured I had consistent anti-alias effects on the diagonals, and wasn't overdrawing any lines. This meant I had to precompute the vertices, and order them by y-axis then x-axis before entering the drawing loops.