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.

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)) → headless image; .png_bytes() for notebooks; dart.gui.orbit_camera(...) / look_at(...)
• 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 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.