Load skin sprites dynamically ?

SEB

Hello,
It's been a long time since I used Spine. I was wondering if it's possible to have a character with different skins and having each skin sprites exported separately and load them only when the skin is applied ?
Thanks

Misaki

SEB It is possible to pack the images for each skin into a specific texture atlas page, but the skin information itself cannot be exported separately and is always bound to a single skeleton data. In other words, in the usual way, all atlas texture page images associated with a skeleton are loaded when that skeleton is loaded.

If you are concerned about load times for a skeleton with a large number of skins, we recommend using Spine Addressables Extensions. This module covers all necessary steps to automatically replace your textures with low-resolution placeholder textures and loading the high-resolution textures upon request. The textures are automatically replaced with the low-resolution texture when building your game executable via a pre-build step (and reset to the high-resolution textures afterwards in the post-build step). It requires no additional coding and is easy to use, so please give it a try.

SEB

Hello there,
I'm not really concerned with load times but with memory consumption. In my case a skin is a whole set of sprites, meaning all sprites are different from one skin to another, and there will be a lot of skin (50-100). Therefore I don't want all skin sprites to be loaded when the skeleton is loaded but only when the skin is selected.
Does that make sense ?
Best,

Misaki

SEB To reduce memory consumption, you can reduce draw calls by using the Skin.GetRepackedSkin() method, which allows you to combine used texture regions of a collected skin to a single texture at runtime. See the Runtime Repacking section of the documentation for more information:
https://esotericsoftware.com/spine-unity-main-components#Runtime-Repacking

Please also have a look at the example scenes as recommended in the documentation.: Spine Examples/Other Examples/Mix and Match and Spine Examples/Other Examples/Mix and Match Equip.

SEB

I'm not really talking about draw calls but sprites loaded in memory. It's not possible to let 50-10 skin assets/sprites loaded at the same time. So I'm trying to find a way to load skin sprites/spriteAtlas only when the skin is selected/applied. Is that possible ?
Best

Misaki

SEB Assuming that the "skin sprites/spriteAtlas" you are referring to corresponds to texture atlas pages, I would like to provide the following explanation.

When loading a skeleton, all texture atlas pages associated with that skeleton are generally loaded as well. This behavior is due to Unity's inherent design, where all referenced assets are automatically loaded, making it difficult to completely avoid this.

Therefore, instead of trying to load textures when the corresponding skin is applied, a more practical solution would be to use a system like Spine Addressables Extensions. This system loads all textures when the skeleton is loaded, but first uses low-resolution placeholder assets. High-resolution textures are then loaded and swapped in only when the appropriate skin is selected.

If there is a specific reason you cannot use Addressables, or if you are considering using a different asset management system, could you share your requirements or constraints with us? We would be happy to explore alternative solutions.

SEB

" Assuming that the "skin sprites/spriteAtlas" you are referring to corresponds to texture atlas pages, I would like to provide the following explanation." That : I was wondering if skin assets could be packed on separate sprite atlas ? It could (?) allows to load sprite atlas only when required (eg: when the associated skin is applied).

Best

Misaki

SEB Thanks for the clarification. As mentioned before, it is possible to pack each texture atlas page for each skin. However, this does not mean that the textures can only be loaded when the skin is applied. Since Unity loads all indirectly referenced assets, indirectly referenced by the SkeletonDataAsset, which references the Atlas asset, which references all atlas pages as materials with the atlas texture page texture. Thus, by default, all exported textures are referenced and thus loaded by Unity when the skeleton is used in a Unity scene.

To dynamically load only the atlas for the selected skin, using Addressables is the recommended approach. This allows you to manage memory effectively by loading and unloading textures as needed.

Davide

SEB

You can read more about our Texture Packer here. In the example, the same skeleton's textures are packed first into a single sprite; then into two separate sprites, once per skin.

But as Misaki said, even if you pack skins into different sprites, the atlas text file (the one that ends with .atlas) will hold references to all the sprites. This implies that once the .atlas file is loaded, all sprites are loaded too.

Addressables provides a strategy to have a better control on sprite loading.

SEB

Thanks for the clarification. So if I summarize :

Skin sprites can be packed on different atlas
Using Addressable Extension those atlas can be loaded on-demand

Am'I right ?
Thanks

Misaki

SEB Since you seem to be trying to understand the exact information, let me correct you on a minor detail.
In Spine, we do not usually refer to them as "skin sprites". The packed images used in the skeleton are called atlas “page images”.
If you simply say "atlas", it would be confusing with a text file with the .atlas extension. Since only one text file with the extension .atlas is exported per skeleton or multiple skeletons, it is not split per page image. Rather, it serves as a guide to identify the split page images as all being for a single skeleton.
Putting these together, your following sentence would be correct if you had said "texture atlas", but incorrect if you just said atlas, because it looks as if you are splitting a text file:

Skin sprites can be packed on different atlas

The following sentence should likewise say "texture atlas", not simply "atlas".

Using Addressable Extension those atlas can be loaded on-demand

If what you were imagining in your head was a texture atlas, then your understanding is correct.

If the terminology is not consistent, we will inevitably need this extra explanation of what each other stands for, and I think it is a good idea to read the user guide again carefully, as Davide recommended.

If memory consumption becomes a problem after testing, feel free to ask us again.

SEB

Hi Misaki,
Your right, I meant texture atlas - thanks for your clarification, it is really helpful !
Best