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.

Type	Simulates	Use for	Selection data	Cost
BoneCloth	Transform chains	hair, tails, cords, skirts with bones	auto (root=Fixed, rest=Move)	low
MeshCloth	mesh vertices (proxy)	skirts/capes without bones, on the skinned mesh	mandatory (else nothing moves)	high — desktop/console
BoneSpring	spring on Transforms	chest/butt jiggle, soft secondary motion	auto	low

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

File	Covers
mcp-authoring.md	Unity_RunCommand patterns, edit-mode persist via LoadPrefabContents, copy+re-target an existing setup, collider creation, selection-data generation, Play-mode testing & scene capture
parameters.md	Every constraint (Force, Angle Restoration/Limit, Distance/Tether/Bending, Inertia, Collision, Self-Collision, Spring), calibration numbers, presets, stylized anime-look recipe, penetration fixes, wind
pipeline.md	How the solver works (PBD-style, 90 Hz substeps, constraint order), update modes, culling, pre-build, v2.8.0 feature gating
pitfalls.md	Failure modes (symptom → cause → fix): Unity crashes, MeshCloth dead, clipping, jitter, scale, update-mode oscillation

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.