sbel-reproducibility

Entry point for FSI-coupled hybrid plans (plan_type=fsi_in_scene) — any scene combining SPH fluid (water tanks, dam-break, wave channels) with multi-body dynamics, optionally with a wheeled vehicle. Pick this over mbs_in_scene whenever the plan involves a fluid domain (scene_objects with domain_type starting "sph_") or an FSI body registration (scene_objects with fsi_registration set). Routes to fsi/sph (always), veh/wheeled_vehicle (when vehicle present), and enforces FSI-specific invariants distinct from generic mbs_in_scene rigid scenes.

Entry point for rigid-body hybrid plans (plan_type=mbs_in_scene) combining a robot or vehicle with scene assets — NO fluid coupling. Routes to the correct domain skills and defines only high-level invariants. Use core/fsi_in_scene instead when the plan involves SPH fluid or FSI body registration.

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.

Entry point for static scene plans (plan_type=scene). Routes the agent to the correct scene, system, and camera skills and defines only high-level invariants.

Set up SPH-based Fluid-Structure Interaction (FSI): create ChFsiFluidSystemSPH and ChFsiSystemSPH, configure fluid and SPH parameters, seed fluid particles with hydrostatic initialization, add container BCE boundary markers, register floating rigid bodies, optionally couple with a wheeled vehicle, and advance with sysFSI.DoStepDynamics(dT).

Translate a `geometry_relations` entry from the plan into correct PyChrono coordinate code. Read this whenever the plan declares a relation_name you have not previously encoded, and especially BEFORE writing SetPos / camera placement for any body that participates in a multi-body geometric constraint. Each subsection below is one canonical pattern named exactly as it appears in `plan.geometry_relations[i].relation_name`.

Create rigid bodies with mass, geometry, collision shapes, and visual assets.

Enable contact detection using the correct contact material for NSC or SMC systems.

Finite Element Analysis — beam elements, tetrahedral solid elements, MKL solver, HHT timestepper, breakable constraints, FEA contact surfaces.

Quaternion creation, component access, and Euler angle conversion in PyChrono

Run the time-stepping loop, collect data, and post-process results with matplotlib or CSV.

Create and configure a PyChrono ChSystem, gravity, contact method, and solver.

Joint topology, kinematic constraints, and elastic links for MBS. Covers revolute, prismatic, motors, springs, axis-aware joint frames, general revolute hinge alignment (local +Z to physical axis) plus special planar cases, and correct topology for mechanisms with ground pivots and fixed guides.

Mandatory asset discovery protocol for project-local and Chrono built-in assets.

Procedure for grounding scene plans in attached reference images — enumerate, describe, orient, then derive predicates.

Output format specification for simulation plans — Markdown sections and current SimulationPlan schema conventions.

Coordinate system, predicate algebra, and orientation rules for PyChrono scene plans. Lets the planner derive concrete (x, y, z, deg_z) by composing predicates instead of guessing.

Create and control a Unitree Go2 quadruped robot from URDF with RL locomotion policy (model_3000.pt), including collision visualization, head collision, contact logging, and complete simulation loop.

Authoritative reference for chrono_code.utils.scene_assets usage — AssetDescriptor + add_visual_assets + convex-hull collision + FootprintRegistry placement. Covers two canonical scenarios (indoor office workstation with repo-local data/scene/ assets, outdoor props for vehicle/robot scenes using Chrono built-in sensor/offroad/ assets).

Attach an RGB preview+recording camera to a body using the project helper setup_preview_camera (returns a CameraRecorder). NON-FSI scenes only — for FSI/SPH scenes use fsi/sph Pattern G + chrono_code.utils.vsg_recording instead, since sensor cameras (OptiX) cannot render SPH particles.

Create and configure a ChSensorManager, add scene lighting, and run sensor update loops. NON-FSI scenes only — FSI/SPH scenes must use fsi/sph Pattern G (VSG-only recording) because OptiX cannot render SPH particles.

Configure interactive, path-following, and data-based driver systems for wheeled and tracked vehicles.

Create rigid terrain patches, SCM (Bekker-Wong soft-soil) terrain, and CRM (SPH) terrain for wheeled vehicle simulations.

Create and configure wheeled vehicles (HMMWV, CityBus, FEDA, custom JSON) with engine, transmission, drive, steering, and tire settings.

Set up and run ChVisualSystemVSG for 3D rendering — window, camera, grid, sky, lights, and render loop.