DART Simulation Verification

Load this skill when verifying that a DART 3D scene or physics simulation is correct — implementing, debugging, benchmarking, or reviewing dynamics, collision, contact, or GUI output. DART's domains need 3D understanding that language models lack natively; this tooling makes it checkable without a GUI.

Lead with text, corroborate with images. Measured A/B evidence: per-step metrics and trajectories detect nearly all seeded physics defects; a rendered image alone misses static geometry defects (penetration, interpenetration). Decide correctness from text; use images for scene comprehension and gross dynamic failures.

Applicability contract

Use this skill for any task whose claim depends on 3D structure or behavior: model/scene loading, dynamics, collision/contact/constraints, simulation stepping, GUI/rendering, or visual examples. First run a text oracle (metrics, scene diff, trajectory/contact comparison, or focused behavioral test), then corroborate it end to end with an assessed headless view and only the debug layers needed by the claim. If rendering is unavailable or genuinely irrelevant, record why and name the replacement evidence; never treat an image as the sole correctness oracle.

Full documentation

docs/onboarding/agent-sim-verification.md — the durable guide. docs/ai/verification.md owns the gate policy; docs/onboarding/profiling.md owns text-first profiling.

Quick commands

Text (primary):

• world.compute_step_metrics() — energy/momentum/penetration/contacts/residual
• dartpy.dump_scene_json(world) / dump_scene_text(world) — "what is in this world?" (glTF/USD-flavored hierarchy + flat index)
• pixi run scene-diff — structural JSON verdict for intended-vs-actual scene dumps
• pixi run trajectory-record / pixi run trajectory-compare — per-body TSV + contact JSONL; bit-exact or tolerance diff with first-divergence

Visual (corroboration):

• dart.gui.render(world, camera=None, size=(w, h), debug=(...layers...)) → headless image with optional world-derived debug layers (grid, world_frame, body_frames, coms, inertia_boxes, collision_bounds, velocities, contacts, labels; trajectories additionally requires a sampled dart.gui.TrajectoryTracker via debug_scene_for_world); dart.gui.render_annotated(...) composites label text; .png_bytes() for notebooks; dart.gui.orbit_camera(...) / look_at(...)
• dart.gui.assess_view(world, camera, size, focus=...) → ViewReport with issues (cropped/too-far/too-close/occluded/ambiguous); dart.gui.select_viewpoints(...) picks deterministic best views; dart.gui.frame_body/frame_region reframe onto a subject. Assess first; fix flagged views before capturing evidence.
• viewer camera flags: --view {three-quarter|front|side|top}, --camera-azimuth/-elevation/-distance/-target, --turntable N, --fit
• pixi run py-demo-capture — headless PNG/MP4 capture from Python
• pixi run agent-capture — deterministic evidence harness: auto/explicit cameras, debug layers, stills/turntable/motion video, reproducible sidecar
• pixi run image-compose — side-by-side / blend / diff-heatmap composites
• pixi run evidence-select — claim-driven artifact selection with recorded rationale; pixi run evidence-publish — PR "Visual verification" section with GitHub-hosted media (manual placeholders by default; gh-release upload only with --yes + maintainer approval)
• pixi run image-verdict / image-golden / image-sheet — JSON verdict, golden diff, contact sheet (contrast is report-only; --require-contrast to gate)
• pixi run image-ab-study — blind-judge detection deltas for single-view, multi-view, turntable, and annotated captures
• pixi run image-ab-round2 — prepare a blinded round-2 packet and score completed judge observations

Opt-in:

• pixi run render-golden-gate — opt-in golden gate (backend-specific golden, curated locally with -- --update; not default CI)
• pixi run rerun-trajectory — rerun.io inspection (opt-in; graceful when rerun-sdk is absent)
• pixi run verification-bundle — package text evidence plus still/grid images for a provider-neutral VLM or reviewer call

Default capture for agent review: one ~1280 px frame, UI hidden, 3/4 view; add a 9-frame grid for motion. Keep images as corroboration, never the sole oracle for static geometry.

DART 6 (release-6.20)

Equivalent capture over OpenSceneGraph: dart::gui::osg::setUpOffscreenViewer / captureOffscreen + dartpy bindings, pixi run capture (needs a real X server or Xvfb), the ported image tooling, and pixi run bm-boxes-headless for rendering-free determinism checksums.