Spine Pixi Runtime

[badlogic]

See #2299

TODO

• Code review
• Assets should be copied to the example dir via examples/export/runtimes.sh.
• Add license header to all files where needed.
• Formatting
• Add JSDocs to public API
• Check if batching actually works as intended, specifically with (dark) tint, and benchmark
• Add support for PMA atlases if necessary
• More examples
• Documentation page
• Release to NPM

[davidetan]

This 0ac67cf should address PMA.

[davidetan]

I've quickly tried Darktint and Pixi 8.

• Darktint doesn't seem to work. It must be manually enabled passing a DarkTintMesh factory, but doing so breaks PIXI.

• Pixi 8 doesn't work (probably expected since Pixi 7 is declard as a peer dependency). It simply fails to start complaining about dynamic requires.

[davidetan]

DarkTint actually works, but it has to be enable manually.
With 098fc08, we changed this. DarkTintMesh is automatically used if at least a slot has dark color, so DarkTint renderer is registered by the runtime at import.
User can still decide to pass the default Mesh Renderer during Spine object creation.

[davidetan]

Check if batching actually works as intended, specifically with (dark) tint, and benchmark

Batching works, both normally and with dark tint.

Care should to set PIXI.Mesh.BATCHABLE_SIZE at a reasonable size (default is 100) because reasonable sized meshes in Spine easily reach this number.
For example, raptor example body has 314 vertices, and consequently breaks rendering in three batch unless PIXI.Mesh.BATCHABLE_SIZE is increased.

Benchmarks

On a 13-inch, 2018 MacBook Pro with:

• CPU: 2,3 GHz Quad-Core Intel Core i5
• GPU: Intel Iris Plus Graphics 655 1536 MB
• Memory: 16 GB 2133 MHz LPDDR3

Using raptor-pro - it uses default Mesh Renderer (no dark tint).
Setting PIXI.Mesh.BATCHABLE_SIZE = 158; (158 * 2 = 316 > 314 raptor vertices).

We can get:

• Up to 24 raport in 1 draw calls
• Up to 49 raport in 2 draw calls
• Up to 73 raport in 3 draw calls
• Up to 98 raport in 4 draw calls

Using raptor-pro - and passing the Dark Tint Renderer has the very same result as above.

Blending modes
Using blending modes interrupt batching as explained in Pixi doc.

Caveats on using Dark Tint Renderer
DarkTintRenderer of spine-pixi is a subclass of Pixi BatchRenderer. This implies that using it will break batching since webgl has to switch shader.