Partial loading of skeleton to reduce memory usage

jimanjr

Hey there,

I've noticed a few topics related to saving memory from large spine projects.

We are currently using 4 skeletons with a total of 90+ skins on them (different character, 4 body types).
We have successfully exported each skin to a different atlas by packing folders separately. This was necessary to solve size issues with the atlas. Each skin is either 512x1024 or 1024x1024.

We are trying to reduce the amount of memory the characters use since we have a maximum of 4 of those on screen at all times.

From all the information that I can gather I came up with 2 solutions and am looking for a bit of help implementing one:

We could export 1 skeleton per skin so that we use the same loading code with no changes and only load needed characters. Sadly there is no such option in the command line so we kinda need to hack the skeleton JSON ourselves which I am not that happy about
We could remove the atlas reference from the spine components at build time and assemble our atlas at runtime matching the desired skin (with a custom AtlasAttachmentLoader I assume). Not too keen on this one since we can't see the results in the editor. And remaking the atlases in the editor as well sounds like a pain. Especially for keeping the ability to easily choose skins from the inspector and such

I think the easiest and safest to implement would be the first one, but before I go ahead and start hacking the skeleton, is there anything like this coming to the editor soon?

Or are there any ideas? Has anyone else found a solution for this issue?

Nate

Loading only the images that are needed may be necessary if there are many, but it is usually not worth reducing the skeleton data loaded into memory. How much memory does the skeleton data take up?

assemble our atlas at runtime matching the desired skin

Packing an atlas at runtime with only the images you need is a little more complex than loading an entire atlas that is already packed, but it is otherwise a good approach.

And remaking the atlases in the editor as well sounds like a pain.

Not sure what you mean by this, especially since you say you already pack a separate atlas per skin. The editor always uses individual images.

Not too keen on this one since we can't see the results in the editor.

Why wouldn't you be able to see the attachments in the editor? You can show/hide attachments to see a particular mix of attachments. You can also use skins to group attachments, then show multiple skins at once.
Skins - Spine User Guide

Your AttachmentLoader can discard attachments by returning null. Check the explanation in the second half of this post:
Multiple Map Workflow (Normal, Mask, Emission, etc.)

jimanjr

Hi Nate, thanks for the reply!

I think I used some confusing terminology so I'll try my best to clarify.
When talking about partially loading a skeleton, I mean specifically the textures that it references.
When we load a character prefab, the dependency chain looks something like this:

Prefab > SkeletonDataAsset > SpriteAtlasAsset > 35 materials > 35 textures.

Due to the way Unity works, once I reference the prefab, everything else gets loaded. The idea that I talked about above is severing the link between SpriteAtlasAsset and the materials and rebuilding it when needed. Alternatively severing the link between SkeletonDataAsset and SpriteAtlasAsset. In this case there would probably be missing info that would affect our editor workflow (not 100% sure on this one, but I think some of the inspector functionality relies on info from the SpriteAtlas?)

That's why I mostly leaned toward the other option where we add another step between the artist exporting the characters and importing them into Unity, where we multiply each skeleton a few times, but only link each instance to one skin. Then our loading would look like this:

Prefab > SkeletonDataAsset > SpriteAtlasAsset > 1 material > 1 texture

With no additional hacks. However that tool would need to be kept up to date with the spine JSON format. That's why I was asking if there is any plans to support exporting a single skin and its attachments (from a multi-skin project) as a separate skeleton file. And if so, if you guys have any ETA on that.

Nate

We don't support exporting a skeleton with only part of the data because it is not an issue to load all the skeleton data. The skeleton data is already completely separate from the images / texture atlas so, for example, exporting a skeleton multiple times with only one skin is not a good solution. That would require many exports, duplicating much of the skeleton data in each, and in some cases require the same duplicate data to be loaded multiple times.

The thread I link discusses your use case. You can load all the skeleton data without loading any images. You can either pack multiple atlases and load only the atlases you need, or you can put individual images into your app and pack only the images you need at runtime.