Change tileset definition to avoid renumbering tiles when image width changed

[bjorn]

One problem that's common enough to cause quite some pain is that when a tileset's image width is changed, this causes all the tiles in the tileset to get renumbered. This in turn messes up any tile references from tile layers and tile objects (also affecting object templates) and requires a lot of custom code to fix (a workflow that has always been somewhat broken, see for example issues #1770 and #1851). Even tile references within a tileset definition, like for terrain images, animation frames or Wang sets need adjustment.

I'm considering a solution where adjustment to other assets is entirely avoided, by keeping the tile IDs stable (still pointing to the same location in the image). To achieve this, we can store for each tile its x and y coordinate on the tileset image. Then, when the image has grown in size next time the tileset is loaded, any new tiles will get added to the end of the list, receiving new IDs just like when adding images to an Image Collection tileset.

It would be interesting to store also the width and height of each tile, such that we can at the same time support tilesets that contain tiles of varying sizes (issue #1008), if we add some UI to manage the tiles in a tileset.

One question is what to do when the user changes the parameters of the tileset, like when halving or doubling the tile size. On the one hand, we can't expect this will keep any map using that tileset to still look alright, so it might be OK to just renumber all tiles in this case. On the other hand, this may commonly happen after changing the resolution of the tiles:

• User changes tileset image to a version 2x bigger
• Tiled detects more tiles on the image (actually 4x the amount of tiles), new tile IDs are added
• User changes tileset tile size

Probably, at the last step, Tiled should make an effort to match up tiles based on the old and new size parameters, making sure their IDs stay the same.

[bjorn]

As eishiya pointed out on the forum, in the interest of compatibility it would be a good idea to introduce a new type of tileset for this purpose. This way Tiled can still support the old method where tiles would get renumbered and limit or hide the UI actions, depending on whether the tileset is marked as "spritesheet" or not.

[bjorn]

Suggested format for storing the sub-rectangle for each tile:

For image collection tileset:

<tileset firstgid="1" name="objs" tilewidth="2000" tileheight="2000" tilecount="63" columns="0">
 <grid orientation="orthogonal" width="384" height="332"/>
 <tile id="0" x="0" y="0" width="160" height="192">
  <image width="160" height="192" source="alter.png"/>
 </tile>

For tileset based on tileset image:

<tileset name="Desert" tilewidth="32" tileheight="32" spacing="1" margin="1">
 <image source="tmw_desert_spacing.png" width="265" height="250"/>
 <tile id="0" x="1" y="1" width="32" height="32"/>

Alternatively, a child subrect could be considered, but I think it's not an improvement:

 <tile id="0">
  <subrect x="1" y="1" width="32" height="32"/>
 </tile>

And for JSON:

"tiles":[
 {
  "height": 192,
  "id":0,
  "image":"alter.png",
  "imageheight":192,
  "imagewidth":160,
  "width": 160,
  "x": 0,
  "y": 0
 }, 

Placing this information on the tile object makes sure we can support this feature for both tileset images and image collections.

This approach does exclude image layers, and they already have x, y, width and height attributes, so if this is to be supported for image layers we'd need to use different names there or a child element. Personally I think it would be better to add support for the image layer features to tile objects. That's only locking and image repetition, where the latter should probably be added to tiles.

[eishiya]

I'm in favour of <tile id="0" x="1" y="1" width="32" height="32"/>.

I'm also still against the idea of using Tile Objects as replacements for Image Layers. The subrect child approach or uniquely named properties would be better IMO. It's not consistent with tiles, but Image Layers are not tiles, so I think that's fair. That's not to say Tile Objects shouldn't get these extra properties, I just don't think an overlap in features makes Image Layers obsolete. Image repetition means something different for Tile Objects than it does for Image Layers. On image layers, the idea is infinite repetition, the image is drawn as many times as needed, typically used for background and foreground decoration. Tile Objects have a finite size, repeating an image is useful for e.g. platforms made out of some tile (especially if combined with snap to grid for resizing).

[bjorn]

On image layers, the idea is infinite repetition, the image is drawn as many times as needed, typically used for background and foreground decoration.

This is also one of the problems of image layers in the context of a world though, so I was considering to crop them at the map size. Of course, it may need to be optional in case there is really a use-case for infinite repeating. Alternatively, the option to repeat infinitely could be added to tile objects... ;)

[eishiya]

This is also one of the problems of image layers in the context of a world though, so I was considering to crop them at the map size.

This sounds reasonable, if it's optional. I like to see the infinite repeating on my maps, as it makes it very clear what I'm looking at. I think it would be more intuitive for people new to the feature for the repeating to not be clipped by default, as on smaller maps, the repeat feature may appear to do nothing if clipping is enabled. Unclipped layers are also useful for cases where you have non-repeating but large image layers, such as parallax layers. Perhaps image layers could be clipped only when Show World is enabled and a World is loaded?

Infinitely repeating Tile Objects seem like they would only be useful in scenarios where Image Layers would be a cleaner option xP Though now you've got me thinking it might be cool to be able to assign a tile instead of an image to an Image Layer, so that someone using a background atlas can define all their different backgrounds and then just pick them as needed. Of course, at that point, the argument for using a Tile Object is pretty strong, the only argument against being that you need a layer and an object, and a layer+object for each additional background if they have different parallax values, instead of just an Image Layer, and the associated processing involved with objects in-game (either treating them as dynamic all the time, or taking special care to turn them into static entities at parse-time).

[UliAbo]

That all sounds really like a great feature!

Just from my understanding: When this feature is implemented, I can define (GUI-wise) within a single Tilset multiple Tile sizes? Like based on a "least common divisor" like 16x16px? So I can define Tiles like 16x16 and 32x32 but also non-square ones like 64x32, etc.? That would be really cool as then we could make our game setup much easier, especially when using Tilesets in ObjectLayers.

Did I understand this correctly?

[eishiya]

@UliAbo It's even better than that: you can define tiles of any size, so you can define some tiles that are 16x16, 64x32, etc, but you can also define tiles that are 14x20 or any other size that fits in the image. It would be like having an Image Collection in terms of flexibility, except all the images are arbitrary regions from a single image.

However, you bring up an interesting feature idea: the ability to snap to some grid while defining tiles would be very useful, as many tilesets have tiles designed to be used as multiples of some base tile, and defining larger tiles is just to make them more convenient for e.g. Tile Objects.

Here's a visual example, I used Rectangle Objects on a map to show what tile definitions might look like in this Tile Atlas tileset type: Most of these are multiples of 16x16px, but the two little trees near the centre are 16x19, and the larger tree above them has two tiles defined that overlap, one of them excludes the transparent padding.

On a related note: this tileset type, along with Image Collections, really calls for per-tile draw offsets xP

Edit: Tileset source & credits: https://www.deviantart.com/chaoticcherrycake/art/Pokemon-Tileset-From-Public-Tiles-358379026

[UliAbo]

@eishiya That would be really wonderful to have! And yes, such a "grid" would be convenient, especially for me also to prevent any mis-definitions of Tiles.

It looks like there's a lot of interest in this feature. Is this already in development, maybe with a rough release schedule in mind?

[eishiya]

No, it's not in development yet AFAIK, since the current focus is on finishing 1.9.

There are also a question about how these tilesets should be displayed:

• Maybe there should be two view modes in both the Tileset Editor and Tilesets panel, "Image" and "Tiles"? "Image" would show the tileset image and the definition regions, which is great if your original tileset is organized and there's minimal overlap, and "Tiles" would show the tiles as if it were an Image Collection, showing overlapped tiles completely separate, and not showing any part of the image that isn't defined as a tile. Tile rearranging would only be relevant in "Tiles" mode. I think selecting tiles and adding terrains, etc should be possible in Image Mode, though overlapping tiles will get in the way of that.
• A "highlight hovered tile" option similar to the one for Objects would be useful to show which tile will be affected by whatever you're doing. This would be useful in the Tilesets Panel too, when selecting tiles. It should be optional just like "highlight hovered objects" since for non-overlapping tiles, it might just be distracting.
• For drawing terrains on overlapping tiles in "Image" mode, perhaps the selected tile(s) should be favoured? If none or multiple of the candidate tiles is selected, then use the tile that's sorted last ("on top").
• Maybe the "Image" mode should also be available for regular "Based on Image" tilesets, which would show the excluded margins and spacing. This would be useful for people trying to adjust their tileset properties.

Oh, another feature idea: Since the main goal of this tileset type is to prevent issues when people change the width of the tileset image, that means it's expected that people will change the size of the tileset image. Tiled needs to make it easy to define the newly added tiles, ideally with some sort of action that defines all the not-yet-defined regions of the tileset based on the tileset's grid settings (which would presumably be set during the tileset creation and optionally used to define the initial tiles).

[bjorn]

No, it's not in development yet AFAIK, since the current focus is on finishing 1.9.

Well, I was recently distracted a little bit and did do some work towards this feature while I helped finish #3339 and then worked on #3359. Though granted, these changes only lay some foundations and no UI work has yet been done, and indeed I think the UI work will stay out of scope for 1.9.