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physics-sim

Design & creation

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Updated 10-31 12:23

About this skill

Physics Sim

Stable rigid/soft body setups. Motivated destruction. Baked caches.

When to Use

  • Rigid body interactions and collapses
  • Soft body jiggle / rubber / simple soft props
  • Destruction and debris (cell fracture / pre-cut shards)
  • Pre-vis physics before VFX polish

Workflow

Simplify collision meshes → Assign rigid/soft bodies
  → Constraints → Passive settings → Bake → Art-direct → Export cache

Rigid Body Quick Rules

Role Settings notes
Active Moving debris / props
Passive Floors, walls, heavy anchors
Convex hull Fast, approximate
Mesh Accurate, heavier
  • Apply scale before sim
  • Use margin appropriate to scale
  • Collection: COL_Physics_[Shot]

Constraints

  • Hinge / fixed / motor for mechanical links
  • Breakable constraints for destruction beats
  • Name: RBCON_[Object]_[Type]

Destruction Approach

1. Pre-cut shards (cell fracture or manual)
2. Island meshes as active rigid bodies
3. Passive shell until trigger frame
4. Animate trigger (force / keyframed activation)
5. Bake → cleanup interpenetrations

Soft Body

  • Prefer for simple soft props; use cloth-sim for garments
  • Goal weights to retain shape
  • Soft + collision object required

Bake / Export

  • Bake to cache before render
  • Alembic/USD for cinematic debris
  • For games: bake key poses or flipbook; rarely live Blender physics

Constraints

MUST DO

  • Apply scale; use simplified colliders
  • Bake before final delivery
  • Trigger destruction intentionally (frame)

MUST NOT DO

  • Write code or snippets for Blender versions before 5.2, or add version fallbacks: this plugin targets 5.2+, and legacy branches teach users APIs that no longer exist
  • High-res sculpt meshes as active colliders
  • Unbounded shard counts
  • Leave sims unbaked for final renders

Scripts

Tested on Blender 5.2 LTS via the official Blender MCP. Run with execute_blender_code (or headless, see the blender-mcp-workflow skill); read the script header for every argument. When the user will paste code into Blender themselves, give them the short runpy call with the absolute path of this installed script and their ARGS. Don't inline or rewrite the script: the tested file is the point.

Script What it does
scripts/rigid_body_setup.py Set up rigid bodies: ensure a rigid body world, make objects ACTIVE or PASSIVE with a collision shape and mass from a material density, configure the cache range, and optionally bake. 
import runpy
result = runpy.run_path("<skill_dir>/scripts/rigid_body_setup.py", init_globals={"ARGS": {...}})["result"]

ARGS: active, passive, shape, material, frames, substeps, bake

Reference Guide

Topic Reference Load When
Rigid Body Presets references/rigid-body-presets.md When needed
Destruction Pipeline references/destruction-pipeline.md When needed
Sim Bake Checklist references/sim-bake-checklist.md When needed