Spaitial PlayCanvas World

Use this skill to one-shot a playable PlayCanvas starter from a Spaitial world. The starter must work in-browser without manual debugging: visible splat, collision mesh, physics actor, sensible controls, debug view toggles, and a successful build.

Non-Negotiables

• Treat every level as having both a visual splat and a collision mesh.
• Use the collision mesh as source of truth for collision, debug mesh view, spawn, and bounds. Manifests are metadata only.
• Spaitial API splats are .spz; PlayCanvas gsplat does not load .spz directly. Convert .spz to a PlayCanvas-compatible binary little-endian Gaussian splat .ply, then load that .ply.
• Pin Vite to the Rollup line. Do not use vite@latest; Vite 8/Rolldown can break PlayCanvas gsplat workers with __publicField... is not defined.
• Disable PlayCanvas unified gsplat mode: entity.addComponent("gsplat", { asset, unified: false }). Unified sort worker has crashed in this setup.
• Use explicit paths: npm --prefix "<project>" ... and absolute paths in conversion/download scripts. Cursor shell cwd can drift into a monorepo.
• Add controls and debug toggles by default. A generated app is not done until it is playable.

Prompt Construction

When generating from text, rewrite the user prompt into an empty environment. Always append:

No people, no humans, no characters, no crowds, no portraits, no mannequins, no animals, no visible body parts.

Avoid franchise wording if the API rejects the prompt. Preserve the visual intent with original phrasing.

Example:

User: "generate a 70s classroom"
Prompt: "An empty 1970s classroom interior with rows of wooden desks, chalkboard, warm film-era lighting, educational posters, linoleum floor, windows, period-correct furniture. No people, no humans, no characters, no crowds, no portraits, no mannequins, no animals, no visible body parts."

API Flow

Use SPAITIAL_API_KEY from env when available. If the user explicitly provides a key, use it but do not print it in summaries.

1. POST /v1/worlds with input.type: "text", validation.skip: true, private visibility, and an idempotency key.
2. Poll /v1/worlds/requests/:id/status until COMPLETED.
3. Download visual splat:

curl -sSL -H "Authorization: Bearer $SPAITIAL_API_KEY" \
  "https://api.spaitial.ai/v1/worlds/requests/$REQ_ID/splat" \
  -o "$LEVEL_DIR/world.spz"

1. Start and poll simplified mesh export:

curl -sS -X POST -H "Authorization: Bearer $SPAITIAL_API_KEY" \
  "https://api.spaitial.ai/v1/worlds/requests/$REQ_ID/exports/mesh-simplified"

curl -sS -H "Authorization: Bearer $SPAITIAL_API_KEY" \
  "https://api.spaitial.ai/v1/worlds/requests/$REQ_ID/exports/mesh-simplified"

1. When export is READY, download download_url to mesh_simplified.ply.

Project Defaults

Create a new Vite app folder, usually under ~/Documents/workspace/<level-id>-playcanvas.

Use these package constraints:

{
  "type": "module",
  "scripts": {
    "dev": "vite --host 0.0.0.0",
    "build": "tsc --noEmit && vite build",
    "preview": "vite preview --host 0.0.0.0"
  },
  "dependencies": {
    "@dimforge/rapier3d-compat": "latest",
    "playcanvas": "latest"
  },
  "devDependencies": {
    "@types/node": "^24.0.0",
    "typescript": "^5.8.0",
    "vite": "^6.4.2"
  }
}

Build and run with:

npm --prefix "$PROJECT_DIR" install
npm --prefix "$PROJECT_DIR" run build
npm --prefix "$PROJECT_DIR" run dev

Asset Layout

Use public/levels/<level-id>/ for Vite:

public/levels/<level-id>/
  manifest.json
  world.spz              # original API artifact
  world.ply              # PlayCanvas-compatible converted visual splat
  mesh_simplified.ply    # collision/debug mesh

Manifest should point PlayCanvas at world.ply, not world.spz:

{
  "version": "1.0",
  "id": "level-id",
  "name": "Readable Name",
  "description": "Short description",
  "transform": { "origin": [0, 0, 0], "scale": 1.0, "upAxis": "y" },
  "bounds": { "min": [0, 0, 0], "max": [0, 0, 0] },
  "splats": [{ "url": "/levels/level-id/world.ply", "format": "ply" }],
  "collision": [{ "url": "/levels/level-id/mesh_simplified.ply", "format": "ply" }],
  "spawns": [{ "id": "main", "name": "Main Spawn", "position": [0, 0, 0], "rotation": 0, "isDefault": true }],
  "hotspots": [],
  "spatial": { "cellSize": 5, "nearRadius": 15, "farRadius": 30 }
}

After parsing mesh_simplified.ply, write real post-transform bounds into the manifest.

SPZ To PlayCanvas PLY

Install converter deps in a local venv:

python3 -m venv "$PROJECT_DIR/.venv-spz"
"$PROJECT_DIR/.venv-spz/bin/pip" install "spz @ git+https://github.com/nianticlabs/spz" numpy

If pip/git fails in a sandbox with hook permission errors, rerun outside the sandbox.

Create scripts/convert-spz-to-playcanvas-ply.py that:

• loads spz.load_spz(input)
• reads positions, colors, alphas, scales, rotations
• writes binary little-endian PLY with vertex properties:
• x y z
• f_dc_0 f_dc_1 f_dc_2
• opacity
• scale_0 scale_1 scale_2
• rot_0 rot_1 rot_2 rot_3
• maps SPZ quaternion x,y,z,w to PlayCanvas rot_0=w, rot_1=x, rot_2=y, rot_3=z
• supports --max-splats; default to full quality (0) unless perf is too slow. If downsampling, say so explicitly.

Run with absolute paths:

"$PROJECT_DIR/.venv-spz/bin/python" "$PROJECT_DIR/scripts/convert-spz-to-playcanvas-ply.py" \
  "$PROJECT_DIR/public/levels/$LEVEL_ID/world.spz" \
  "$PROJECT_DIR/public/levels/$LEVEL_ID/world.ply" \
  --max-splats 0

Collision PLY Loader

Implement a runtime PLY parser for the simplified mesh:

• Support binary little-endian and ASCII fallback.
• Read vertex x, y, z regardless of property order/type.
• Read face list indices and triangulate polygon faces by fan.
• Apply Spaitial/SuperSplat PlayCanvas transform to collision: (x, y, z) -> (-x, -y, z).
• Flip triangle winding after mirroring: append triangles as [face[0], face[i + 1], face[i]].
• Compute post-transform AABB.
• Create RAPIER.ColliderDesc.trimesh(vertices, indices) on a fixed rigid body.

Use the same transformed vertices for a debug mesh overlay.

PlayCanvas Splat Loading

Load the converted world.ply:

const asset = new pc.Asset("world-splat", "gsplat" as never, { url });
app.assets.add(asset);
app.assets.load(asset);

const entity = new pc.Entity("world-splat");
(entity as any).addComponent("gsplat", { asset, unified: false });
entity.setLocalEulerAngles(0, 0, 180);
app.root.addChild(entity);

Do not point this at world.spz; that produces Invalid ply header.

Spawn And Camera Defaults

Resolve spawn from the mesh, but tolerate imperfect generated collision:

• Try center X/Z first, then rings around center.
• Raycast downward against only the level collider.
• Require upward-ish normal (normal.y >= 0.35).
• Validate capsule/sphere clearance against only the level collider.
• If no clean spot exists, fall back to bounds.minY + radius + 0.1 and warn.

Default camera collision should be off because generated meshes often include roofs/exterior shells; hard clamping can make zoom-out go black. Add a C toggle to enable camera collision for debugging.

Playable Ball Defaults

Use a dynamic ball unless the user explicitly asks for an avatar. Tuned constants:

const MOVE_FORCE = 0.38;
const VERTICAL_FORCE = 0.42;
const JUMP_IMPULSE = 1.85;
const MAX_SPEED = 3.8;

RAPIER.RigidBodyDesc.dynamic()
  .setLinearDamping(2.4)
  .setAngularDamping(1.9);

Controls:

• W / S: forward/back relative to camera. Forward is {-sin(yaw), -cos(yaw)}.
• A / D: strafe relative to camera.
• Arrow keys mirror WASD.
• Q / E: down/up impulse.
• Space: jump. Ground ray must ignore the ball body and filter to the level collider by handle.
• R: reset actor to resolved spawn/origin and zero linear/angular velocity.
• Mouse drag: orbit camera.
• Wheel: zoom.
• C: toggle camera collision.
• M: toggle collision mesh overlay.
• P: splat only.
• O: mesh only.
• B: both splat + actor, mesh hidden.
• 1-5: spawn another colored physics ball each press/click. Do not toggle/remove existing balls; repeated presses should keep adding balls, with slight spawn scatter so they do not overlap exactly.

Default Side Control Panel

Every generated app should include a polished side control panel, not only keyboard shortcuts. Keep keyboard shortcuts working, but expose the main actions as clickable buttons.

Required panel groups:

• Header with level name.
• Movement group:
• Reset button (R)
• Camera collision toggle (C)
• Short helper text for WASD/arrows, Q/E, Space, drag, wheel.
• View group:
• Splat + Actor (B)
• Mesh Overlay (M)
• Splat Only (P)
• Mesh Only (O)
• Colored Balls group:
• Five color swatch buttons for red, blue, green, yellow, purple.
• Buttons map to 1-5.
• Each click spawns another ball, same as pressing the number key.

Panel behavior:

• Buttons should have active state for current view mode and camera collision.
• Ball buttons should look like spawn buttons, not toggles. Do not keep them active after click.
• Use a clean glassy side panel over the canvas: rounded corners, translucent dark background, subtle border/shadow, readable labels, keyboard hints in <kbd>.
• Keep the panel compact enough for laptop screens and add a mobile fallback that stretches across the top.

Debug Mesh Overlay

Build a PlayCanvas pc.Mesh from transformed collision vertices and indices. Display the simplified mesh as explicit triangle-edge line geometry, not RENDERSTYLE_WIREFRAME, because explicit edges show many more lines and make the mesh easier to inspect.

const mesh = new pc.Mesh(app.graphicsDevice);
const linePositions = createTriangleEdgePositions(collisionMesh);
mesh.setPositions(linePositions);
mesh.update(pc.PRIMITIVE_LINES, true);

const material = new pc.StandardMaterial();
material.diffuse = new pc.Color(0.1, 0.85, 1.0);
material.emissive = new pc.Color(0.08, 0.65, 0.9);
material.opacity = 0.72;
material.blendType = pc.BLEND_NORMAL;
material.cull = pc.CULLFACE_NONE;
material.depthWrite = false;
material.update();

const meshInstance = new pc.MeshInstance(mesh, material);

Expected Output

When asked to create a PlayCanvas world/app, produce:

• API submit/poll/download script or executed commands.
• package.json, tsconfig.json, index.html, src/*, README.md.
• public/levels/<id>/manifest.json.
• world.spz, converted world.ply, and mesh_simplified.ply.
• Runtime PLY collision parser, SPZ-to-PLY converter script, Rapier physics, spawn resolver, camera, side control panel, keyboard controls, repeated colored-ball spawning, mesh/splat toggles.
• Successful npm --prefix "$PROJECT_DIR" run build.

If anything was downsampled, explicitly tell the user the source count and output count.