trimesh-sim

name	trimesh-sim
description	Use when driving Trimesh (pure-Python triangular-mesh processing library) via Python scripts — load STL/OBJ/PLY/3MF/GLB, compute volume / area / inertia / convex hull / signed distance / ray casts, repair non-watertight meshes, boolean ops, sample points — through sim runtime one-shot execution.

trimesh-sim

You are connected to Trimesh via sim-cli.

Trimesh is the standard Python library for triangular-mesh manipulation (Dawson-Haggerty et al.). Pure Python on top of NumPy/SciPy with optional acceleration (rtree, embree, mapbox-earcut, scikit-image). Pip-installable (pip install trimesh).

Scripts are plain .py:

import trimesh
m = trimesh.load('part.stl')
print(m.volume, m.area, m.is_watertight)
if not m.is_watertight:
    trimesh.repair.fix_normals(m)
    m.fill_holes()
m.export('repaired.stl')

Same subprocess driver mode as PyBaMM / PyMFEM / SfePy.

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base/ — always relevant

Path	What's there
base/reference/workflow.md	Load → inspect → repair → analyze → export.
base/reference/properties.md	Volume, area, inertia, COM, convex hull, bounds.
base/reference/repair.md	fill_holes, fix_normals, fix_winding, merge_vertices.
base/reference/operations.md	Boolean (union/diff/intersection), section, slicing, ray casts.
base/snippets/01_props.py	Verified box + sphere volume/area E2E.
base/known_issues.md	numpy bool serialization, watertight check, library deps.

sdk/4/ — Trimesh 4.x

• sdk/4/notes.md — version-specific surface notes.

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Hard constraints

1. m.volume only meaningful for watertight meshes. Always check m.is_watertight first, repair if needed.
2. Boolean ops require a backend (manifold3d, scad, or blender). m.intersection(...) raises if none is installed; install pip install manifold3d for pure-pip.
3. JSON-serialize numpy bools / floats explicitly: cast via bool(...) / float(...) — numpy.bool_ is NOT json-serializable.
4. Acceptance != "ran without error". Validate volume/area against analytical (e.g. box V=LWH, sphere V=4/3πr³) for primitives, or against a known-good reference STL for complex geometry.
5. Print results as JSON on the last stdout line.

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Required protocol

1. Gather inputs:
   • Category A: input mesh path or generation params, expected property bounds, acceptance criterion.
   • Category B: repair tolerance, sampling density, output format.
2. sim check trimesh.
3. Write .py per base/reference/workflow.md.
4. sim lint script.py.
5. sim run script.py --solver trimesh.
6. Validate JSON.