Shader maps world coords to UV via:
gUv = rotated / uGroundSize + 0.5
rotated = 0 -> canvas centre
But drawTileAt placed tiles at:
canvasX = (lng + halfLong) * TILE_SIZE
canvasY = (perp + halfPerp) * TILE_SIZE
With halfLong = 12 and lng iterating [-12..12], tile lng=0 lands
at canvas X = 3072 - but the shader wants gUv.x=0.5 (rotated=0)
at canvas centre X = 3200. Half a tile off.
Fix: shift drawing by +0.5 tiles so each tile CENTRE is at
(lng, perp), matching the shader's rotated-frame interpretation.
Tile centres now align with shader expectation; previous half-tile
diagonal wobble gone (which is what they meant by 'x und y
vertauscht' - the perpendicular axis was indeed offset).
Richard Zink
14fda4c7d6