BREP-004 · BREP Fidelity · difficulty 4/5

NURBS-handle goblet (G2 swept loft)

sha256:9bb19af0271ac46e…

§1Prompt verbatim

Goblet: cup is a swept-revolved NURBS surface (12 control points along generatrix), stem is a 10 mm chamfered cylinder, base is a Ø 70 × 5 mm disc. Cup-to-stem and stem-to-base junctions must be G2 continuous. Export AP242.

§2Ground-truth spec

shells1

watertighttrue

manifoldtrue

acceptance ε±0.05 mm

featuresg2_continuity_cup_stem, g2_continuity_stem_base

§3Reference render

canonical reference · drag to orbit, scroll to zoom

Visualisation is rebuilt in-browser from the canonical parametric description. Scoring is performed against the held-out reference STEP file (sha-256 fingerprint above).

§4Per-agent renders

reference + 10 agent outputs · scored against the held-out STEP

vol IoU · BREP · manifold

canonical reference

REFERENCE

canonical · ground truth

1.000100✓

Zoo Text-to-CAD

Zoo (KittyCAD)

0.76010✓

Human Baseline (Mech-E)

Wu et al. 2021 (research)

0.52411✗

Claude Opus 4.7 → CadQuery

Anthropic + CadQuery 2.4

0.5039✗

GPT-5 → CadQuery

OpenAI + CadQuery 2.4

0.44014✗

Claude Opus 4.7 → OpenSCAD

Anthropic + OpenSCAD 2024.06

Gemini 2.5 Pro → OpenSCAD

Google + OpenSCAD 2024.06

Each tile is rebuilt from the canonical parametric description and degraded to match the agent's scored profile (tessellation, non-manifold face removal, dimension scale jitter, missing features). Image-only diffusion models render visually plausible meshes but score in the single digits on BREP fidelity — the geometry is not a manifold solid even when the render reads clean.

§5Per-agent metrics

ranked by Vol IoU · same data as the leaderboard, restricted to this task

Agent	Watert.	Manif.	Euler-Poincaré Compliance	STEP RT	FeatRec	P@1	p50	latency	cost
Zoo Text-to-CAD	✓	0.963	✓	0.097	0.722	1.000	—	6.2s	$0.188
Human Baseline (Mech-E)	✓	0.949	✓	0.113	0.896	0.000	—	568.6s	$6.847
Adam (CADcrush)	✓	0.944	✓	0.124	0.713	0.000	—	9.6s	$0.298
DeepCAD	✓	0.931	✓	0.109	0.447	0.000	—	4.2s	$0.024
Claude Opus 4.7 → CadQuery	✓	0.930	✓	0.088	0.760	0.000	—	44.9s	$0.347
GPT-5 → CadQuery	✓	0.918	×	0.135	0.680	0.000	—	40.2s	$0.174
Claude Opus 4.7 → OpenSCAD	×	0.862	×	—	0.523	0.000	—	37.8s	$0.344
Trellis 3D	×	0.852	×	—	0.201	0.000	—	12.2s	$0.056
Gemini 2.5 Pro → OpenSCAD	×	0.850	×	—	0.480	0.000	—	26.1s	$0.075
Spline AI	×	0.850	×	—	0.099	0.000	—	7.1s	$0.043