Minimal 3x3

Class: PentaTileLayoutMinimal3x3

Minimal 3x3 is the 9-tile cardinal-edge minimum. It maps the 16 possible edge-mask states onto a 3x3 grid with an open-side collapse rule.

This is the layout to try for RPG Maker A2-like ground art, legacy Godot 3.x style atlases, and quick low-detail prototypes.

Template

Atlas contract

Property	Value
Grid	3 columns x 3 rows
Tile count	9
Mask bits	T=1, E=2, B=4, W=8
Dispatch	open-side collapse rule
Grid type	single-grid
Rotation reuse	none

Setup

1. Add PentaTileMapLayer.
2. Set layout to PentaTileLayoutMinimal3x3.
3. Arrange the atlas like a classic 3x3 autotile block: exposed top row, center row, exposed bottom row.
4. Paint normally.

Open-side collapse

The layout chooses a column from west/east openness and a row from top/bottom openness:

• west open only -> column 0
• east open only -> column 2
• neither or both -> column 1
• top open only -> row 0
• bottom open only -> row 2
• neither or both -> row 1

This means some 16-state masks share the same tile. That loss is the tradeoff that makes the 9-tile minimum possible.

Authoring notes

• Use full-cell artwork because this is single-grid.
• mask=0 dispatches to the center tile (1, 1) so isolated cells render.
• This layout is intentionally compact; use Wang 2-Edge if the 3x3 collapse is too lossy for your art.