Add Spine 4.0 Plugin Support

[epreston]

Add Spine 4.0 Plugin Support

• Add media and examples for Spine 4.0 runtime
• Update build system to create 4.0 plugin
• Add prebuilt plugin
• Update docs, minor tool adjustments
• New Owl demo is kinda fun.

Replaces: #78

Fixes a gap in the support matrix.

I confirm I have read the contributing guidelines and signed the Contributor License Agreement.

[epreston]

@mvaligursky had to redo the PR so it was up to date with the 4.1 support.
Nearly have it working except 4.0 demos will not display. No errors.
I think it might have something to do with the texture.

[epreston]

Raptor 4.0 should look identical to Raptor 4.1 demo. Nothing displays for 4.0
Owl 4.0 demo should look like the following. I hope to use the owl so each version has a unique looking demo. Currently, nothing displayed for 4.0 but everything loaded, no errors.

[epreston]

If I modify the json file version of the owl demo and use 4.1 library, the owl demo works without modification. If I use the 4.0 library, no errors, but nothing displays.

To reproduce, modify spine40/demos.json, 4th line:

    "spine": "4.1.23",

In the owl40.html modify the 43 nd line:

new pc.Asset("playcanvas-spine.4.1.js", "script", { url: "../build/playcanvas-spine.4.1.js" }),

[epreston]

For version 4.0, it looks like textures are accessed through the "page" property. For RegionAttachment and MeshAttachment we need to make the following adjustments.

The following:

// create / assign material
if (attachment.region && attachment.region.texture) {
    const texture = attachment.region.texture.pcTexture;

Becomes:

// create / assign material
if (attachment.region && attachment.region.page.texture) {
    const texture = attachment.region.page.texture.pcTexture;

[epreston]

Ready for review, please be sure to check out the Owl demo.

If two raptor demos is confusing, I can remove the 4.0 version.

[epreston]

One area of improvement that needs an engine / graphics expert. The grey outline makes me think the pre-multiplied alpha is wrong. The plugin just assumes this is:

material.blendType = pc.BLEND_PREMULTIPLIED;

I've seen data files that have a "pma" attribute for textures, which we could read and honour. Thing is, this is something that I get wrong all the time. It could just be that its on a grey background. I don't know.

The first screenshot above is from the original spine demo, outlines are nice and crisp. In that demo they are using an alphaTest threshold of 0.5, I don't know what the equivalent or how that is achieved in PlayCanvas Engine.

[mvaligursky]

Top contribution, much appreciated!