What the geometry gate rejects (paper-thin parts, zero volume, and more)

Before a generated part is accepted, the HIIE Engine runs a structural geometry gate. Its job is to catch output that technically "built" but isn't actually a usable part, so you don't end up archiving junk geometry.

What the gate flags

The gate (verifyGeometry) rejects output that shows any of these problems:

• No solids — the result contains no solid bodies.
• Empty GLB — the viewable file came back empty.
• Paper-thin parts — the smallest dimension is under 0.4mm.
• Extreme aspect ratio — proportions of 150:1 or worse.
• Zero-size bounding box — the part has no measurable extent.
• Near-zero volume — under 1 mm³.

Why it exists

Geometry can compile successfully and still be degenerate — a sliver, a wisp with no real thickness, or a shape with effectively no volume. These would be useless for CAD work or 3D printing. The gate is one stage inside the vision quality loop: it runs right after generation, before snapshots are rendered and reviewed, so the refinement passes can correct course.

What this means for you

You generally won't see rejected geometry — the loop catches it and refines toward a valid part within the pass budget. If your prompt describes something physically implausible (extremely thin or vanishingly small), giving real millimeter dimensions and a clear single-part description helps the engine produce something that clears the gate on the first try.