# VRM to Spritesheet

- https://www.youtube.com/watch?v=z_oDpQ4vzNA
- https://hackmd.io/@XR/avatarlod#Webaverse-Pipeline

Sprites can help with optimization, like generating imposters that improve concurrent user count with assets that look like the original custom avatar.

## Character Studio Pipeline

- https://github.com/m3-org/CharacterStudio

using character studio to generate the sprites, example animation / manifest file



It works with different sized models as well


---

### r3f-sprite-animator

- https://codesandbox.io/p/sandbox/r3f-sprite-animator-s12ijv?file=%2Fpublic%2Fboy_hash.json%3A1%2C1-204%2C2

{"frames": {

"Celebration_000":
{
	"frame": {"x":1,"y":1,"w":560,"h":440},
	"rotated": false,
	"trimmed": false,
	"spriteSourceSize": {"x":0,"y":0,"w":560,"h":440},
	"sourceSize": {"w":560,"h":440}
},
"Celebration_001":
{
	"frame": {"x":1,"y":443,"w":560,"h":440},
	"rotated": false,
	"trimmed": false,
	"spriteSourceSize": {"x":0,"y":0,"w":560,"h":440},
	"sourceSize": {"w":560,"h":440}
},
"Celebration_002":
{
	"frame": {"x":1,"y":885,"w":560,"h":440},
	"rotated": false,
	"trimmed": false,
	"spriteSourceSize": {"x":0,"y":0,"w":560,"h":440},
	"sourceSize": {"w":560,"h":440}
},
"Celebration_003":
{
	"frame": {"x":1,"y":1327,"w":560,"h":440},
	"rotated": false,
	"trimmed": false,
	"spriteSourceSize": {"x":0,"y":0,"w":560,"h":440},
	"sourceSize": {"w":560,"h":440}
},

https://twitter.com/antpb/status/1752868882291790262

> The biggest thing we need is a list of standard animations. My current implementation is
> - idle
> - idleBackward
> - walk
> - walkBackward
>
>For jumps you could use the walk animation clamped to a frame where the leg is forward. These are all very old problems though so I’m sure there’s some very standard way that is a one file sheet. The names matter most because the implementations could just not care what the animations do and play on the state associated like walk

---

## Notes

- https://community.khronos.org/t/adding-billboard-sprites-to-gltf/106664
- https://x.com/UX3DGpuSoftware/status/1461706770309689348?s=20
- https://registry.khronos.org/glTF/specs/2.0/glTF-2.0.html#morph-targets


{
    "Apple": {
        "frame": {"x":292,"y":304,"w":60,"h":61},
        "rotated": false,
        "trimmed": true,
        "spriteSourceSize": {"x":23,"y":29,"w":60,"h":61},
        "sourceSize": {"w":90,"h":90},
        "pivot": {"x":0.5,"y":0.5}
    },
    ...
}

snippet from Eidur in Webgamedev discord
> I'm implementing vanilla three and threlte components and utilities at the same time.

export type SpritesheetFormat = {
  frames: [x: number, y: number, w: number, h: number][];
  animations: Record<string, [frameId: number, duration: number][]>;
  sheetSize: [w: number, h: number];
  animationLengths: number[];
};

---

## glTF extension notes

rough sketch by lasershark

{
  "extensionsUsed": ["m3_spritesheet_animations"],
  "images": [
    {
      "uri": "data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAA..."
    }
  ],
  "extensions": {
    "m3_spritesheet_animations": {
      "spritesheets": [
        {
          "image": 0,
          "name": "Sprite Animations",
          "dimensions": { "width": 1024, "height": 1024, "framesH": 4, "framesV": 4 },
          "frameRate": 12,
          "animations": [
            { "name": "walking", "startFrame": 0, "endFrame": 3, "loop": true },
            { "name": "jumping", "startFrame": 4, "endFrame": 7, "loop": false }
          ]
        }
      ]
    }
  }
}