# Four-Legged Monsters Through SCAIL 2

Every Sprute animation so far has been driven by Template-kun, a humanoid. Materia needs monsters, and a wolf can't walk the way Template-kun does.

The good news: in Sprute, SCAIL 2 doesn't take keypoints. Its pose video is a gray, shaded render of a skinned mesh. So any rigged mesh should be able to drive it, not just a person.

## Setup

- **Rig:** Quaternius' CC0 husky from Poly Pizza. It comes with its own Idle, Walk and Gallop clips.
- **One option:** `--motion` takes the GLB. A humanoid skeleton is still played by Template-kun. Anything else, like this husky, plays on its own body. `--own-body` forces its own body even for a humanoid, and `--clip` picks the animation.
- **Design:** Nano Banana Pro painted the wolf directly over a render of the rig's first idle frame, so the reference already stands in the driver's pose.

```bash
sprute animate character --character dusk --motion husky.glb --clip Walk --directions 4
```

Only the four diagonals are drawn (NW, NE, SW, SE). About 80 to 140 seconds of GPU per clip.

## Results

Walk, first seed:

![Wolf walk, four diagonals](https://cdn.hashnode.com/uploads/covers/682665f051e3d254b7cd5062/49061241-13f5-4bf8-9f59-a832e697db54.webp)

Idle, first seed:

![Wolf idle, four diagonals](https://cdn.hashnode.com/uploads/covers/682665f051e3d254b7cd5062/5492d4df-81e2-48fe-8403-f77260ff5263.webp)

Gallop, first seed:

![Wolf gallop, seed 11](https://cdn.hashnode.com/uploads/covers/682665f051e3d254b7cd5062/4655ad65-deed-4414-ab72-ee76bda38b2e.webp)

The full stretch is clean. Where all four legs gather under the body, the SW and SE views still smudge the lower legs, at every seed we tried.

### The first gallop's ghost legs were our bug

The first version of this post showed a gallop with ghost legs and blamed SCAIL 2. The driver was the problem. This husky attaches its paws to IK control bones, and its clips move those bones rather than rotate them. Our renderer only applied the root's movement, so the legs swung while the paws stayed behind, folded and dragging. SCAIL 2 drew exactly what it was shown. Driver before the fix (top) and after (bottom):

![Gallop driver before and after the IK-foot fix](https://cdn.hashnode.com/uploads/covers/682665f051e3d254b7cd5062/5457d024-2e72-41b6-9dfe-a042785f0a6d.png)

## The check doesn't see legs

Our check compares each frame to the character's own direction views with image embeddings: identity, facing, coverage and colour. It passed every wolf clip with the thresholds we set for humanoids, and it still caught a wolf that was turned around (swapping the diagonals sent every frame negative).

But it scored the ghost-legged gallop from the broken driver the same as a clean one. An extra leg barely moves an embedding. For fast quadruped motion, someone still has to look.

## The slime needed no model at all

A slime has no limbs, so there's nothing for SCAIL 2 to do. Nano Banana Pro painted the four diagonal views, and a small script squashes and stretches each view about its bottom centre, keeping the area roughly constant: a slow breath for idle, and a hop for walk (crouch, launch tall, fall, land flat, wobble back). It runs in under a second.

![Slime idle](https://cdn.hashnode.com/uploads/covers/682665f051e3d254b7cd5062/3a17e58c-62e4-4ff2-a524-5721776e7388.webp)

![Slime hop](https://cdn.hashnode.com/uploads/covers/682665f051e3d254b7cd5062/1d0eb8ec-535b-487d-b1a0-d20b9461311d.webp)

## Next steps

- Find a signal for ghost legs.
- Keep the gathered gallop legs apart, perhaps by shading near and far legs differently in the driver.
- Try more rigs: something with six legs, something with wings.

‒ Sprited Dev 🐛