Magica Cloth 2

Magica Cloth 2 (code-first authoring via Unity MCP)

Set up and tune cloth simulation on a Unity character without clicking the Inspector — by running C# in the Editor through the Unity MCP Unity_RunCommand tool. Magica Cloth 2 exposes its entire config as a public ClothSerializeData plus a BuildAndRun() entry point, so every Inspector action is reproducible from script. This is validated ground truth on v2.8.0 (full C# source under Assets/Plugins/MagicaCloth2/).

The look lives in authored data (cloth type, vertex/bone selection, collider placement, constraint curves), not in code. Plan the data first; the solver is fixed.

Prerequisites (verify, else stop)

1. Magica Cloth 2 present. Assets/Plugins/MagicaCloth2/ (or a UPM package). Check the version in .../Editor/EditorExtension/AboutMenu.cs — feature gating depends on it.
2. Unity MCP connected. Unity_RunCommand, Unity_ManageEditor, Unity_ReadConsole available. If not, stop and tell the user.
3. Target character with a humanoid/skeleton rig and SkinnedMeshRenderer(s). For MeshCloth, the source mesh must be Read/Write ON and Optimize GameObjects OFF.

Decision: pick the cloth type first

Everything downstream depends on this. See pipeline.md for internals.

The #1 gotcha: MeshCloth auto-selection fills every vertex Invalid → the cloth does nothing. You must supply selection data (paint, paint map, or attribute array). BoneCloth/BoneSpring auto-generate a usable selection. Prefer BoneCloth for new elements when bones exist; reserve MeshCloth for boneless geometry on the body mesh.

Quick start — BoneCloth from script (runtime build)

Run via Unity_RunCommand (class must be internal CommandScript : IRunCommand). Build (BuildAndRun) only runs in Play mode; in edit mode just set data and let Start() auto-build at play. Full MCP recipes (edit-mode authoring that persists, copying an existing setup, colliders, re-targeting) are in mcp-authoring.md.

using MagicaCloth2; using UnityEngine; using Unity.Mathematics;
internal class CommandScript : IRunCommand {
  public void Execute(ExecutionResult result) {
    var go = GameObject.Find("Character/Hair");
    var cloth = go.AddComponent<MagicaCloth>();
    var sd = cloth.SerializeData;
    sd.clothType = ClothProcess.ClothType.BoneCloth;          // [NG] runtime: set before build
    sd.rootBones.Add(GameObject.Find("hair_root_L").transform);
    sd.gravity = 3.0f;
    sd.damping.SetValue(0.05f);
    sd.angleRestorationConstraint.stiffness.SetValue(0.15f, 1.0f, 0.15f, true);
    sd.colliderCollisionConstraint.mode = ColliderCollisionConstraint.Mode.Point;
    result.RegisterObjectCreation(go);                         // undo tracking
    // cloth.BuildAndRun(); // only in Play mode; otherwise Start() auto-builds
  }
}

Workflow

1. Inspect. Read the rig, renderers, existing cloth/colliders with a lightweight Unity_RunCommand (component type names only — never dump SkinnedMeshRenderer data, it crashes Unity). See pitfalls.md.
2. Choose type (table above). Confirm Read/Write for MeshCloth.
3. Colliders first. Add MagicaCapsuleCollider/MagicaSphereCollider on body bones (thighs, hips, head, chest). Uniform global scale only or collision fails.
4. Author the cloth. Set SerializeData; for MeshCloth also supply selection data. Register colliders in colliderCollisionConstraint.colliderList.
5. Parameters. Start from a preset, then tune Angle Restoration first (it dominates motion), then Inertia, then collision. Calibration table in parameters.md. For a stylized cel-shaded / anime look (readable, bounded, snappy secondary motion), use the bone-based types and the tuning recipe in parameters.md.
6. Build & test. Enter Play (Unity_ManageEditor Play), confirm each cloth IsValid()==true, capture the scene, compare. See mcp-authoring.md.
7. Verify console (mandatory): Unity_ReadConsole with Types:["Error","Warning","Log"], grep error CS / Exception. Fix before declaring done.

Runtime-change rule

• [NG] fields (set before build, never after): clothType, sourceRenderers, rootBones, connectionMode.
• [OK] fields (gravity, radius, damping, constraints): after changing at runtime, call cloth.SetParameterChange(). After changing a live collider, call collider.UpdateParameters().

Reference map

Version note

This skill is validated on 2.8.0. Absent before later versions: distance culling (2.10), collider symmetry ColliderSymmetryMode (2.15), batch jobs (2.14). Camera culling, self-collision, and pre-build are present. Check AboutMenu.cs and confirm an API exists before using it; see pipeline.md.