How to use the 3D Falling Leaves agent skill

What an agent skill is and what this one does

An agent skill is a folder containing a SKILL.md file of instructions that an AI agent loads when a task matches the skill's description. This one is not a ready-made program. It tells the agent how to build the effect.

The core idea is that each leaf turns through its face, edge and back while drifting sideways. The edge-on moment is what sells the effect, so the skill says to use a two-sided quad or lightly bent mesh rather than camera-facing point sprites, which cannot turn edge-on. It also covers shared wind, hiding leaves inside buildings, and recycling leaves near the camera so the count stays efficient.

• Two-sided leaf meshes with a recognisable silhouette, stem and restrained veins
• Tumble and sideways drift coupled together, with persistent seeded per-leaf values
• A common wind field with small per-leaf variation
• InstancedMesh or instanced attributes for moderate to large counts
• Camera-aware spawn and wrap boundaries, with soft fades
• Occlusion handling so leaves do not fall inside rooms

Install the skill from the ZIP download

Download the ZIP for the skill from this page. The skill is in the agent-skills/3d/3d-falling-leaves folder of the MengTo/Skills repository, licensed MIT. Unzip it so the folder containing SKILL.md sits in one of the following locations.

For a personal install, place it in ~/.claude/skills/. For a single project, place it in the project's .claude/skills/ folder. Alternatively, in the Claude apps you can upload the skill under Settings → Capabilities → Skills.

• Personal: ~/.claude/skills/3d-falling-leaves/
• Project: .claude/skills/3d-falling-leaves/ inside your project
• Claude apps: Settings → Capabilities → Skills, then upload

Trigger the skill with natural requests

You do not need a special command. The skill's description says to use it for 3D autumn leaves or drifting foliage in Three.js and similar scenes. Describe what you want in plain words that mention the 3D scene and the engine.

If you want a flat 2D overlay instead, ask for that directly. The skill itself says to use the separate falling-leaves skill for 2D canvas overlays.

• "Add 3D autumn leaves drifting past the trees in my Three.js scene."
• "Make leaves tumble and slip sideways in the wind, with a few close ones and many distant ones."
• "Stop leaves from falling inside the cabin roof in this Three.js scene."
• "Give me a 2D falling-leaves overlay for my landing page."

Work through the build in order

The skill recommends starting with one slow leaf before increasing the count. Verify that one leaf completes a tumble and a full fall cycle, with a visibly different face and back and a thinning edge, before scaling up.

Keep the random values persistent. Each leaf gets seeded values for position, scale, phase, tumble rate, roll rate, fall speed, lateral slip and palette variation. The skill warns never to generate new random values every frame.

For sideways motion, the lateral offset follows the tumble. The skill gives this closed form for angular speed omega bounded away from zero: angle = phase + omega × time, and sideOffset = −(slip / omega) × cos(angle). Its derivative is slip × sin(angle), so a leaf slips fastest when edge-on.

Scale up with instancing and recycling

For moderate counts, use an InstancedMesh with reusable CPU scratch objects. For larger fields, use instanced attributes and shader animation. Upload seeded attributes once and update only time, wind, season amount and camera anchor uniforms.

Centre the recycling volume ahead of the camera along its horizontal viewing direction, with a fallback direction when looking nearly straight up or down. Move the spawn and wrap boundaries as the camera moves rather than parenting live leaves to the camera. Wrap leaves outside the visible volume and fade them near boundaries. The skill's fade formula is 1.0 - smoothstep(inner, outer, distance), where inner must be less than outer.

Start sparse, then tighten the visible volume before increasing the count. Keep the nearest leaves from covering the camera as large blurred shapes.

Integrate with occlusion, shadows and seasons

Depth testing alone does not stop leaves falling inside rooms. The skill says to exclude covered interior volumes or provide roof and terrain collision proxies. For crisp edges it suggests alpha testing with depth writes as a default. Alpha-to-coverage only softens edges when the render target is multisampled.

Match leaf cutouts and wind deformation in any shadow pass, or disable leaf shadow casting if its cost outweighs its visual value. Let seasonal state change palette and active density instead of creating a new leaf system per season.

Safety notes: scripts and network

The skill's metadata states that it runs no scripts and uses no network access. It is a set of written instructions for the agent. Review the generated code as you would any code, because the agent still writes the project's files.

The guide refers to the Seijaku reference implementation for the closed-form falling-leaves pattern. Access to it is needed only if you want that pattern. The REFERENCES.md file links to a specific commit of that project on GitHub, along with the Three.js InstancedMesh and Material docs. Replace Seijaku's hardcoded roof rectangles with your own scene's geometry or volumes.

• Runs scripts: no
• Uses network: no
• Requires a 3D engine such as Three.js or similar

Tips for better results

Describe your scene: engine, camera style, how much of the view the leaves should cover, and where buildings or roofs are.

Ask the agent to verify the reduced-motion case, showing the scene frozen at a composed state.

Ask for overdraw and update-cost measurements rather than assuming particles are free.

Use a padded texture atlas and extend edge colours into transparent texels to avoid dark rims.