User clarified:
- x must decrease left to right (east at screen left, high x left)
- y must decrease in flight direction (south at front, low y in flight dir)
With no swap on canvasY (lng+halfLong+0.5 formula) and UNPACK
flip=true, canvas top -> texture top -> screen top. canvas bottom
-> screen bottom.
So:
- lng=+12 (north, ahead in N flight) -> canvasY=6272 (bottom)
-> screen bottom. User at screen bottom sees north tiles = high y
- south tiles at canvas top -> screen top. User at screen top sees
south tiles = low y. y decreases in flight direction (looking
forward = top of screen = low y).
With no swap on canvasX:
- perp=-2 (east, dx=+2) -> canvasX=128 (left)
- After WebGL (no X flip): east at screen left, west at screen right.
x decreases left to right (east at left, west at right).
Richard Zink
73920d0ce8