mbs

name	mbs
description	Entry point for pure multi-body simulation plans (plan_type=mbs). Routes the agent to the correct mechanics, system, and camera skills and defines only high-level invariants.
compatibility	pychrono >= 8.0
metadata	{"domain":"core"}

Core Skill: MBS

Use this skill when plan_type = "mbs".

This core skill is a router and constraint layer for pure multi-body problems. It does not own concrete body recipes, topology recipes, or scenario-specific camera/body layouts. Those belong to the relevant mbs/* and sens/* child skills.

Responsibility

This core skill covers only:

• pure mechanics with no external mesh-scene pipeline
• which child skills must be read before writing code
• global invariants around system choice, rendering, and camera separation
• high-level dispatch to body, topology, collision, loop, and camera skills

This core skill does not define:

• named scenarios
• detailed body or joint construction recipes
• concrete camera placement formulas tied to a specific mechanism
• utility-specific signatures beyond category-level reminders

Required Skills — read these before writing code

Skill	Why it is required
mbs/system_create	System creation, gravity, solver, collision-system setup
mbs/body_creation	Bodies and visual/collision body patterns
mbs/simulation_loop	Time-stepping structure, stepping order, logging loop patterns
vsg	VSG visualization window setup, camera, grid, sky, render loop
sens/camera	Sensor manager, setup_preview_camera, recorder loop integration

Optional Skills — read if the plan requires them

Skill	When to read
mbs/topology	Joints, links, motors, springs, and constraints
mbs/collision	NSC vs SMC, contact materials, collision shapes
mbs/quaternions	Quaternion construction and rotation rules
mbs/fea	Finite-element modeling

Global Invariants

• Default world convention is Z-up unless a child skill explicitly owns a different convention.
• Use one physical system and keep its contact model consistent with all materials and collision setup.
• VSG window viewpoint and sensor cameras are separate concerns:
  • vis.AddCamera(...) sets the interactive VSG window view
  • setup_preview_camera(...) creates actual sensor-camera output
• vis.AddCamera(...) must be configured before vis.Initialize().
• Do not call chrono.SetChronoDataPath() by default.
• Choose one stepping path and keep it consistent with the owning mechanics abstraction. Do not mix competing stepping APIs unless a child skill explicitly requires it.

Routing Rules

• Need bodies only: read mbs/body_creation
• Need joints / actuators / springs: read mbs/topology
• Need contacts or friction: read mbs/collision
• Need camera output: read sens/camera
• Need pure mechanics only: stay in mbs
• If the request introduces external mesh-scene assets, route to core/scene or core/mbs_in_scene depending on whether there is a moving body

Minimal Category-Level Reminders

• Sensor recording requires setup_preview_camera(); vis.AddCamera(...) alone is not enough.
• Light direction for VSG is category-level VSG configuration; use the owning skill for concrete usage.
• Read the owning child skill for exact APIs and code templates.

What Core Must Not Contain

If you are writing or updating a core MBS skill, do not place these here:

• concrete pendulum, slider-crank, rover, or vehicle recipes
• body-geometry-specific code templates
• exact camera-placement formulas for a named mechanism
• detailed collision recipes owned by mbs/collision
• detailed recorder recipes owned by sens/camera

Those belong in the owning child skills.