[cocos2dx]ETC1 texture in spine animations

LittleIronMan

Hello to all 😃
I want to use the ETC1 compression format for spine animations and improve performance on Android platform, but I can’t add an alpha channel to the texture.
A little search by code revealed the ability to attach a file with an alpha channel using the suffix “@alpha”.
I compress “sleleton.png” animations texture file using TexturePacker in 2 files - “skeleton.pkm” for RGB and “skeleton.pkm@alpha”.
Suffix great works with objects of the Sprite class(i use create() method), but does not work for “spine::SkeletonAnimation”. What can I do about it?
Code:

auto tmpSprite = Sprite::create(animDir + “skeleton.pkm”);
bg->addChild(tmpSprite);
tmpSprite->setPosition(center);

auto tmpSk = spine::SkeletonAnimation::createWithJsonFile(animDir + “skeleton.json”, animDir + “skeleton.atlas”);
tmpSk->setAnimation(0, “static”, true);
bg->addChild(tmpSk);
tmpSk->setPosition(center + Vec2(500, 0));

result:

Left is the Sprite (from the animation atlas)
Right is the spine::SkeletonAnimation, there is no alpha channel

LittleIronMan

Mario

The spine-cocos2dx runtime currently does not support loading of .pkm and .pkm@alpha files. I'm not too familar with the ETC1 + alpha support in cocos2d-x myself, but maybe a few pointers from my end can help you.

The loading of textures in spine-cocos2dx happens here: spine-runtimes/spine-cocos2dx.cpp at 3.7

As you can see, all it does is load a Texture2D from the specified path and sets it on a Spine AtlasPage. That texture is later used by the SkeletonRenderer. The loading code essentially does the same as the Sprite::create code. It uses the cocos2d-x TextureCache to resolve the file. https://github.com/cocos2d/cocos2d-x/blob/v3/cocos/2d/CCSprite.cpp#L179. This means everything will be loaded correctly. The problem is elsewhere.

The problem with ETC1 + alpha is that it will likely require a custom shader to work. The SkeletonRenderer already uses a custom shader so our two color tinting feature works. I couldn't locate the shader used by Sprite in case of ETC1 + alpha, maybe you have more luck. You should then be able to use that shader instead of the one we ship.

LittleIronMan

@badlogic, thank you very much.
Found the right shader for ETC1 format GLProgram::SHADER_NAME_ETC1AS_POSITION_TEXTURE_COLOR_NO_MVP
Need use it in SkeletonRenderer::initialize() method