Dual-grid
A tilemap technique where the visual grid is offset half a tile from the logic grid, so 16 tiles cover every transition instead of 47.
The trick is to place the rendering grid on the corners of the logic cells rather than on top of them. Each visual tile then overlaps exactly four logic cells — its four corners — and only needs to know their types. Four corners with two states give 2⁴ = 16 variants, and they cover every edge and corner case. Compare that with the classic "blob" set of 47 tiles that autotiling derives from a neighbour bitmask.
The cost is drawing on an offset grid and translating between the two, but the art shrinks dramatically: 16 images instead of 47. Oskar Stålberg used the trick in Townscaper, and it spread widely after jess::codes explained it in 2024. It is a relative of marching squares, which does the same corner-to-shape lookup for contour lines.