Block Reality 0.3a

Structural Preview for Minecraft 1.20.1 + Forge 47.x: real finite
element analysis on the blocks you place, from an engine running outside
the game process.

What this preview does

• extracts placed blocks into 6-DOF beam members and MITC4 shell facets
  (floors and shear walls), one structure per connected component
• solves them with self weight plus point test loads (/br load, in kN,
  any direction), off the tick thread, over a zero-copy shared-memory
  transport
• reports per-member and per-plate demand/capacity with the governing
  fibre named, stress contours on the block faces, a section readout
  with the neutral axis, and a linear buckling factor — a slender column
  that "looks safe" on stress says so
• nine structural blocks: three steel sections, plain concrete, timber,
  a brick pier, two slab thicknesses, 20 mm steel plate — and they mix:
  a timber beam on brick piers is one structure, joined where the blocks
  touch, not three that ignore each other
• every number is gated: 251 acceptance checks against closed forms and
  invariants per build, record in evidence/VERIFICATION.md
• one jar to install: the engine travels inside it and unpacks itself,
  verified against a hash recorded beside it, with no network access at any
  point

Commands that change something — /br load, /br unload, /br scan,
/br resolve and /br reset — need operator level 2, which a single-player
creative world has by default. The Stress Glasses need no permission: they
apply one configured downward test load. Reading commands (/br status,
members, section, loads) are open to everyone.

What it deliberately does not do yet

• no fracture, collapse or falling-block consequences — analysis reports;
  nothing breaks or falls
• no construction sequencing, no reinforced-concrete composite sections
  (the concrete beam is honestly plain), no load combinations or wind
• linear elastic only; the buckling factor is the linear onset, an upper
  bound on the real critical load

Install: put blockreality-0.3a.jar in your
mods/ folder and launch the game. That is the whole procedure — the analysis
engine is inside the jar and unpacks itself on first use, to
<game directory>/blockreality/engine/<hash>/. Nothing is downloaded: the
bytes were already in the jar, their SHA-256 is recorded beside them, and
anything that does not match is refused rather than run. A binary you put
there yourself is never touched. Windows and Linux x86-64; on macOS or ARM the
mod plays normally with analysis disabled and says so.

The archive also carries both engines loose, with SHA256SUMS.txt, optional
installer scripts, and instructions in START-HERE.txt and 讀我-中文.txt.
The loose binaries are byte-identical to the ones inside the jar and a build
gate holds them to that; both are byte-reproducible, so building the engine
from source on another machine gives the same hashes.