TheRON
86a47c3c06
No behaviour change. Comments and a FAILURES entry. The Y profile builds a section area of 135.572973 against a recorded 135.574, out by 0.001027, while every other value for that case matches exactly. Three-Fin matches on everything including area. Isolated by probing the reference inside the pinned toolchain image. The hull cap is identical to nine figures, the bare union is identical, and a single filleted pair is identical at 30 vertices and 125.699057 mm2. The difference appears only when the three filleted pairs are combined, and the three pairs, which are related by 120 degree symmetry and must be identical, come back as 125.699057, 125.698029, 125.699057. Cause proven. The arc segment count is a ceiling on a quantity that is frequently an exact integer: a 60 degree half-angle at $fn=48 gives exactly 8. Floating point delivers that as 8.000000000000004 on one corner and 7.999999999999998 on the others, so one corner gets a whole extra segment. The half-angles come from the merged polygon, whose vertices come from the boolean kernel, and BOSL2 clipper and GEOS disagree in the last bit. Reproduced unguarded because the reference is unguarded. Rounding the count before the ceiling was implemented and reverted: it makes the three pairs identical and fixes Y exactly, and breaks Three-Fin, which had been matching to the digit. Three-Fin has the same asymmetry and the oracle records it. BOSL2 tipped the same way GEOS does there and the opposite way on Y. Two consequences for the project rather than the code. Some recorded values encode float noise rather than geometry, so a port that is geometrically more correct than the reference will fail those cases. And the tolerance model may need revisiting: VOLUME_MM3 is compared at the lengths tolerance of 1e-4 despite being area times 100 mm, so a 1e-3 area difference becomes a 1e-1 volume difference. MASS_G is derived the same way. No decision yet. The number of affected cases is unknown and is the only thing that should drive it, and that is not knowable until build() exists and all 123 cases can run.
Mechanical Compiler
Build the capacity to construct real structures from reclaimed and commodity materials, using whatever fabrication is actually to hand — 3D printing, tabletop CNC, welding, cement casting, COTS stock.
The reference case is a faceted timber shell: planar panels meeting along straight fold lines, converging on nodes, sitting on a platform. Buildable without a factory, provided someone has worked out what the pieces are and how they meet. That last clause is the project. The Mechanical Compiler exists to make the pieces computable, qualifiable, and reproducible by someone who was not present when they were designed.
Scope
In scope: geometry, qualification, and reproducibility of structural members and their interfaces.
Not in scope: building codes, permitting, jurisdictional approval. Qualification and compliance are different things. A qualification says this member is what it claims to be, made this way, from this stock. Compliance is a jurisdiction-specific argument someone else may build on top.
The project records physical claims, never verdicts — section modulus, moment of inertia, material provenance, process parameters. Those are what any future argument would need. A pass/fail verdict would bake in a jurisdiction we do not want to be bound to. Measure and attest; never adjudicate.
Repository layout
docs/ specification, state, failure log, roadmap
legacy/openscad/ rev 8.0.0 generators — reference, not a live target
fixtures/ frozen acceptance oracles
tools/reference-toolchain/ pinned OpenSCAD + BOSL2, build-time only
src/mechcomp/ the application
tests/ acceptance against the oracle
Read docs/ROADMAP.md first for what this is, then docs/ENVIRONMENT.md for
how an instance is built. If you are writing provisioning automation, read
docs/FAILURES.md before the specification — every entry is something a
script written from the specification alone would have got wrong.
Getting started
make deps # virtualenv, base + CAD requirements
make verify-oracle # confirm the frozen oracle is intact
make test # pytest -n auto
make verify-oracle needs nothing but Python. It should pass on any machine at
any time; if it does not, stop.
The oracle
fixtures/strap-beam-8.0.0/ holds 123 frozen cases — 113 accepted, 10
rejected — produced by OpenSCAD 2021.01 with BOSL2 at 92d697c2. It is the
acceptance criterion for any reimplementation of the generators.
The ten rejected cases are part of the contract. A port that accepts them is wrong, however good its numbers look elsewhere. It is easy to reproduce the geometry and quietly lose the constraint that made it trustworthy.
The generators under legacy/openscad/ are the reference implementation, kept
so the oracle can be regenerated. They are not a live target and the running
application has no OpenSCAD dependency.
Provenance
This project's documents, code and roadmap are LLM-generated under human direction. That is stated plainly here and in any downstream submission. We do not obscure it.
The maintainer reviews and owns every line. Anything that could not be defended in a review thread does not ship.
Licence
AGPL-3.0-or-later. See LICENSE.
Section 13 obliges us to offer source to users interacting over a network, so any deployed web tier carries a visible link back to this repository. That is a licence obligation, not a courtesy.