Tilemaps and autotiles

[Darkhog]

RPG Maker has nice feature called Autotiles. Those tiles are made so one tile can be shrinked to as small amount as 3x3 tile square plus one tile with cramped corners.

Example autotile

Top-left tile is used only as display of tile in editor, top right contains inside corners of tile. 3x3 tiles square contains outside corners, sides and middle of tile.

Here are tiles that can be made out of this:


(I'm using unofficial Polish translation of RPG Maker XP so title is because of that).

I have pretty much idea how I can break up autotiles and make all those tiles. Problem is another one - how I choose "right" tile so they'll fit together in map?

Let's assume that in following code "0" represent normal tile and "1" autotile. I want to display them properly:

0 0 0 0 0 1 0 0 0 0 0 
0 0 0 0 1 0 0 0 1 0 0
0 0 0 0 1 1 1 0 1 0 0
0 0 0 1 1 1 1 0 1 1 0
0 0 0 0 0 1 0 0 0 1 0
0 0 0 1 1 1 1 1 1 1 0

How can I achieve this?

[Super Vegeta]

I used to check all eight adjacent tiles if they are the same type or not, and then draw the autotile accordingly. I had two variables, one for sides, one for corners. Each of them was actually kind like a 4-bit flag. I set them according to the adjacent tiles, and then I had a huge (16-element, duh) case of sides_variable. Like, if no adjacent autotiles, draw the "single spock", if only one adjacent autotile, draw the connecting gfx on one half, and on the other half draw corners (which can be either inside or outside facing).

If you'd like, I can share some code, but you'll have to give me some time to add comments et cetera so it can be readable.

[Darkhog]

Sure! Will wait.

[Super Vegeta]

Instead of posting actual code, I think I'll just describe the logic I used.

First of all, this code was designed to use a different format of autotiles, like this:

5 tiles placed horizontally: full tile, top & bottom border, left & right border, outside corners, inside corners.

// Bit flags for sides and corners.
const SIDE_TOP = 1; SIDE_BOT = 2; SIDE_LEF = 4; SIDE_RIG = 8;
        COR_TL = 1; COR_TR = 2; COR_BL = 4; COR_BR = 8;

// I assume map to just hold integers with tile types
Procedure DrawMapTile(X,Y : Integer; Gfx : whatever)
Var Edges, Corners : Integer;
begin
Edges := 15; Corners := 15; // All flags set means that autotile is stranded and we have to draw borders.
If (Y = 0) or (Map[X][Y-1] = Map[X][Y]) then Edges -= SIDE_TOP; // We mark top side as no-border
If (Y = (MapH-1)) or (Map[X][Y+1] = Map[X][Y]) then Edges -= SIDE_BOTTOM; // We mark bottom side as no-border
// The same for left
// The same for right
If (X = 0) or (Y = 0) or (Map[X-1][Y-1] = Map[X][Y]) then Corners -= COR_TL; // We mark top-left corner as the same type
// Same for top-right
// Same for bottom-left
// Same for bottom-right
Case Edges of
00: begin // 00 means that all sides are connected. We either have to draw a full tile or an all inside-corners tile.
    DrawFullTile(X,Y);
    DrawCorner(X,Y,Corners,COR_TL);
    DrawCorner(X,Y,Corners,COR_TR);
    DrawCorner(X,Y,Corners,COR_BL);
    DrawCorner(X,Y,Corners,COR_BR)
    end;
01: begin // 01 means that there is a border on the bottom side.
    DrawBorder(X,Y,Edges,SIDE_TOP);
    DrawBorder(X,Y,Edges,SIDE_BOT);
    DrawCorner(X,Y,COR_TL);
    DrawCorner(X,Y,COR_TR);
    end;

Et cetera, et cetera. Edges can be 00-15, so you have 16 cases. DrawBorder() should check if the appropriate edge (SIDE_XXX) flag is set in Edges, and either draw a border or draw the connecting part of tile. DrawCorner() behaves the same way.

This approach requires much copy-pasta and introduces some over-draw, but I've found the easiest to implement in terms of logic.

[Darkhog]

Well, 16 tiles aren't enough.

Sure, you could do tile like this:

-------
|######
|######
|######

or this:

-------
#######
#######
#######

But how about this:

--------
|######|
|######|
|######|

or this:

------
######
######
------

? I know you know RPG Maker because I know you from Polish RPG Maker forum, even you are using same avatar. I want solution like in case of RPG Maker.

Also I've said that I have no problem with breaking autotile into individual tiles, main problem is getting "right" "sub tile" for the job.

//edit: Anyway, I've decided that I'll write "breaker" program that would break autotile into individual tiles and output it into image file. Then in map editor I'd place them manually. Would save myself coding pain.

[Super Vegeta]

It's not limited to 16 tiles, you can do all the shapes an autotile can have on a square map.

-------
|######
|######
|######

Edges = 5 (top + left). Draw left border, top border, top-left outside corner, and then either a continuous tile or inside corner in bottom-right.

-------
#######
#######
#######

Draw top border. Bottom side, each quarter-tile is either continuous or an inside corner.

--------
|######|
|######|
|######|

Draw left, right border, and top inside corners.

------
######
######
------

Draw top and bottom border.

If you forget about the "continuous or inside corner" issue, you only have 16 possible tiles - depending on the four neighbouring tiles: top, bottom, left and right. That's why I wrote about 16 cases. In the cases I draw borders and outside corners, because they depend only on those 4 tiles.

x----
-Xxx
-xxx

We can tell the "big X" must have an outside corner at the top-left, no matter if the (X-1,Y-1) tile is of the same type, or not. So, like I said, checking the 4 neighbours gives me 16 cases, and in every case I know exactly which borders and inside corners I have to draw. Then I only need to check if any of the remaining quarters of the tile should be continuous or have an inside corner.


If it still sounds bizarre, give me a day and I'll write you an example.