Fix: GameMaker Autotile Corner Not Matching

A wall autotile in your dungeon shows the wrong corner shape at concave junctions. The art is correct in the tileset image; the layout configuration is wrong, so GameMaker picks the wrong variant for that neighbor pattern.

Layout Types

GameMaker autotile layouts:

• 16-tile: variants for 4 cardinal neighbor combinations. Simple; works for purely orthogonal layouts.
• 47-tile: variants including diagonals. Required for inner corners on irregular shapes.
• RPG Maker: a 5-frame autotile per cell. Niche.

Your art must match the chosen layout exactly — tile (0,0) is variant 0, (1,0) is variant 1, etc., following the layout’s reference arrangement.

The Fix

1. Open the TileSet asset.
2. Switch to the Autotile editor.
3. Set Auto Tile Layout to match your art (47-Tile for most modern autotile sets).
4. Compare your art to the layout’s reference diagram in GameMaker’s docs.
5. Save and repaint the test area.

Verify Tile Indices

The autotile editor shows each variant’s expected neighbor pattern. Click each tile in the editor; a preview shows which neighbors should be filled for that tile to be picked. If your art at that index doesn’t match the preview, you have the wrong art at that index — rearrange.

Repaint After Layout Change

Changing layout after painting doesn’t auto-repaint existing tiles. Either:

• Repaint manually with the corrected layout.
• Or in code, iterate tiles and call tilemap_set with computed indices.

Verifying

Paint a known-tricky shape: an L-bend, a + intersection, an isolated tile. Each should render with the correct visual variant. Compare to a reference autotile set in GameMaker’s sample projects.

“Autotile picks variants by layout pattern. Layout must match art. Get the configuration right; the rest is automatic.”

When buying or commissioning tile art, specify the layout (16-Tile or 47-Tile) up front — saves rearranging after delivery.