AI Tileset Generator Guide: Seamless Tiles for Top-Down and Side-Scroller Games

A good AI tileset starts with a fixed tile size (16, 32 or 48 pixels), tiles whose edges match on every side they will touch, and a quick 3x3 preview to catch seams before the tiles reach your map. Generate the ground and wall variants in one locked style, fix any visible seam at the edges, then set up autotiling with terrains in Godot or Tiled so transitions place themselves.

This guide covers sizes, why seams appear, the difference between top-down and side-scroller tiles, autotile basics, and a workflow from prompt to a map you can open in your engine.

Pick the tile size first

Tile size	Feel	Common use
16x16	Retro, strong silhouettes, few colors	Platformers, classic RPGs, game jams
32x32	Room for texture and small details	Modern pixel RPGs and action games
48x48	RPG Maker MZ scale	RPG Maker projects and similar top-down games
64x64 and up	Painterly or high detail	Isometric, HD 2D, strategy maps

Characters and tiles must agree. A 32x32 hero on 16x16 tiles reads as a giant unless that is the intent. Decide both together, and keep every tile in the set at exactly the same size.

Why seams appear

A seam is a visible line or a repeating pattern where identical tiles meet. The usual causes:

Edge lighting. The tile is darker or lighter near its border, so a grid of darker lines appears across the floor.
A centered feature. One rock or flower in the middle of every tile repeats as an obvious lattice.
Mismatched edge pixels. The left column and right column do not continue each other.
Gradients. A tile that gets lighter toward the top creates horizontal bands.
Texture bleeding at runtime. With linear filtering or non-integer scaling, the engine samples pixels from the neighboring tile in the atlas. Use nearest filtering, integer zoom, and a pixel or two of padding between tiles in the atlas.

The 3x3 preview test

Place the tile in a 3x3 grid, nine copies touching, and look at it at 100% and at 400% zoom. The center tile is surrounded on all sides, so every edge relationship shows at once.

Look for straight lines along the tile borders.
Squint: if you can still count the tiles, there is a repeating feature that needs breaking up.
Check the corners where four tiles meet; corner pixels often clash even when edges match.
Repeat with two or three variants mixed together, which is how the floor will look in the game.

Any image editor can build the grid. The open source universal-modder CLI has a one-line version, um sprite tile-preview tile.png preview.png, which renders a 3x3 tiling by default.

Fixing a seam

The classic fix is the offset trick: shift the tile by half its width and half its height with wrap around, so the edges move to the center. Repaint the cross shaped seam that appears, then shift it back. GIMP has this under Layer, Transform, Offset; Photoshop under Filter, Other, Offset.

Top-down tiles and side-scroller tiles

Top-down ground tiles are seen from above and must tile in all four directions. Walls are separate pieces, and transitions between materials (grass to dirt, sand to water) need edge and corner tiles.

Side-scroller tiles are seen from the side. The top surface (grass, snow, metal grating) differs from the inner fill, so a platform set needs at least:

[ left cap ] [ top middle ] [ right cap ]     surface row
[ left side ] [ inner fill ] [ right side ]   body rows
[ bottom left ] [ bottom ] [ bottom right ]   underside

Only the inner fill has to tile in every direction. The top middle tile has to tile horizontally, and the caps only connect on one side. Add slopes and one-way platforms later as separate tiles.

Autotile basics

Autotiling picks the right edge or corner tile automatically when you paint a terrain. Two editors cover most 2D work:

Tiled groups tiles into terrain sets. Its terrain documentation describes three types: a corner set, which matches neighbors at corners and needs 16 tiles for a complete set of two terrains; an edge set, which matches at sides and also needs 16 tiles for two terrains; and a mixed set, which matches corners and sides and needs 256 tiles for two terrains, with reduced sets such as the 47-tile blob also supported.
Godot 4 uses terrains inside a TileSet. The Using TileSets page calls terrains a more powerful replacement for Godot 3 autotiles, with three modes: Match Corners and Sides, Match Corners, and Match Sides. Set the tile size before creating the atlas, and keep the atlas texture region size equal to your tile size.

The 16-tile corner set is the best place to start. Each of a tile's four corners is either terrain A or terrain B, which gives 2 x 2 x 2 x 2 = 16 combinations. Draw or generate those 16, assign the corner bits in your editor, and painting a grass patch on dirt produces clean edges without placing a single transition by hand.

A workflow from prompt to map

Lock the style in a Sprixen project with your art style, resolution and view angle. Tiles and characters generated in the same project share palette and detail level.
Generate a tileset from the project's Tileset mode. Pick a type (ground and floor, walls, decorations, or transitions) and describe the material. Each run renders a 4x4 grid of 16 tile variations, asks the model for edges that match when tiles sit side by side, and slices the result into individual tiles at the tile size (32 pixels by default, 16 to 128 through the API).
Generate single custom tiles where you need a specific piece, such as a door or a bridge. A custom tile costs 1 credit and accepts a projection (top down, side view or isometric) and a collision type (walkable, solid or water).
Run the 3x3 test on every ground and fill tile and fix seams with the offset trick.
Assign terrains in Tiled or Godot. The 16 variations are a starting palette; you still decide which tile fills which corner combination.
Build the map. Sprixen's map builder exports a rendered PNG, its own JSON, a Tiled .tmx file, and a Godot 4 .tscn scene with a TileMapLayer and collision.

Prompting for tiles

Describe a surface, not a scene: "mossy cobblestone floor, evenly lit, no central feature".
Ask for even lighting with no vignette, and no shadows cast from outside the tile.
Keep the material and scale identical across variants: same stone size, same grass blade length.
For transitions, name both materials and the direction: "grass edge on the top side, dirt below".
For side-scrollers, state the view: "side view platform top, grass surface on top edge only".

Tile resolution and character resolution are the same decision; the pixel art sizes guide covers how detail changes from 8x8 to 64x64. To generate a tileset in your game's locked style, open a project in Sprixen.

FAQ

What size should game tiles be?

Use 16x16 for retro games, 32x32 for most modern pixel art, 48x48 for RPG Maker MZ, and 64x64 or larger for high detail or isometric art. Keep every tile in the set at the same size and match it to your character resolution.

How do I check if a tile is seamless?

Tile it in a 3x3 grid and look at the borders, the corners and the overall pattern at 100% and 400% zoom. If you can see lines or count the tiles, fix the edges with an offset pass and test again.

How many tiles does an autotile set need?

Tiled's documentation lists 16 tiles for a complete corner set or edge set with two terrains, and 256 for a full mixed set, with reduced sets such as the 47-tile blob also supported. The 16-tile corner set is the easiest place to start.

Why do I see lines between tiles in my engine even though the tiles are seamless?

That is usually texture bleeding: the engine samples a neighboring tile in the atlas because of linear filtering or fractional scaling. Switch to nearest filtering, use integer zoom, and add padding between tiles in the atlas.

Can AI generate a full autotile set by itself?

AI is fast at producing matching variations and transitions in one style, and you should still check edges in a 3x3 preview and assign terrain bits in Tiled or Godot yourself. Treat the generated set as a strong first pass that you finish in the editor.