After swapping axes so lng runs along canvas Y (corridor long
axis), canvas height was still GROUND_CORRIDOR_PERP * 256 = 1280
(only 5 tiles tall). The 25-tile-long corridor was drawn off-canvas,
so only the back 5 tiles (lng -12..-7) were visible. That made
new tiles 'disappear' off the right side and the build appear 90
deg off from flight.
Set canvas height to corridor long (25 tiles = 6400 px) and
canvas width to perp (5 tiles = 1280 px). Now the full corridor
fits on canvas and the visual depth direction matches the
camera's flight direction along canvas Y.
Richard Zink
c2d6fd38ba