Crate pantometry_shape 

Designed geometry as simulation input: a mesh read, measured, and turned into cells.

Every domain in this workspace takes a structured grid — a box of cubes, counts and a cell size. Every 3D file a person designs is a surface: a bag of triangles, or a boundary representation that was tessellated into one. This crate is the bridge, and the bridge is where the physics gets decided.

The cell size decides three things at once, and only one of them is obvious

A caller picking cell_mm is picking, in one number:

• how much of the shape survives. A 0.5 mm rib voxelised at 2 mm is not a thin rib, it is gone, and the simulation runs perfectly well without it;
• the stability limit, and therefore the step count, as dx²;
• the discretisation error of whatever physics runs on it.

The first is the one that has no symptom. A missing feature does not make a solver fail, produce a NaN, or trip the conservation audit — it produces a smooth, plausible answer about a different object. That is the failure this workspace is organised around not having, so this crate’s job is not only to rasterise but to say what the rasterisation lost: see Loss.

What this is not

Not a domain. It depends on pantometry-units and nothing else in the workspace, and no domain depends on it. It produces a predicate; a domain’s fill consumes one. That is the whole coupling, and it means adding geometry cost the ten domains nothing.

Not a mesh library. No refinement, no repair, no boolean operations, no simplification. It reads what a CAD tool exported, measures it, and rasterises it.

STL only, and that is a dependency decision rather than a preference. STEP needs a B-rep kernel and glTF needs a JSON and binary parser; both are external crates, and this workspace gates every one of its twelve through deny.toml. STL is the format every CAD tool exports and it can be read in two hundred lines with nothing added. When a second format earns its dependency it goes beside this one.

Where it sits

  a designed file ──► Mesh ──► Voxels ──► `|i, j, k| voxels.contains(i, j, k)`
                        │         │                        │
                   volume,     Loss:                  Solid3D::fill
                   closed?     what the grid          Block::fill
                               could not hold         Waves::fill

The predicate on the right is exactly the signature those three already take, which is why this needed no change to any of them.

Structs

Loss

What a rasterisation lost, reported rather than left to be discovered.

Mesh

A closed surface as triangles, in metres.

Triangle

One triangle, in metres.

Voxels

A mesh rasterised onto a grid of cubes.