# 2026-07-10 — Implicit Thought surface prototype

```
Type: log
```

## Opening tick

The effects-lab close renderer could only arrange elongated spheres along the
Thought route. That implementation could not produce the binding cohesive,
non-tubular body, internal marbled circulation, or transient strain windows;
it therefore reproduced the explicitly rejected smooth hose / pearl grammar.

## Changed

- Replaced close, high-rate Thought slugs with a CPU implicit field made from
  overlapping flattened pressure lobes and a marching-tetrahedra surface.
- Added a real through-thickness strain window. Eight precomputed presentation
  phases move, open, and seal it without accumulating fluid state.
- Added a custom Bevy PBR extension whose ivory, silver, and gunmetal bands
  advect through the body from the existing effects clock.
- Kept close low-rate, medium, and far representations cheap. They still derive
  solely from authored/readout route, amount, and rate.
- Cached matching frame sets so the twelve-root stress preset shares one mesh
  sequence instead of extracting the same surfaces twelve times.
- Added focused tests for non-empty extraction and the sealed-low-rate /
  open-high-strain field states.

## Evidence

- `liquid_close`, `liquid_medium`, and `liquid_far` hidden captures completed.
- Two independent fixed-step `liquid_close` runs produced the same SHA-256:
  `b99bc92a27265a260f69a0ab654731e5dfead7fada27d8c2e064e4c9325cbcf8`.
- The close capture visibly carries a single folded pressure body, internal
  marbling, and a rounded opening; medium/far still switch to cheaper geometry.

## Defense

Implements `wiki/interface/thought-fluid.md#material-ivory-mercury-against-chalk`
and criterion 6: close high-rate Thought is cohesive, pressure-lobed, visibly
marbled, and capable of a transient window which seals at lower strain. It also
implements `wiki/art/effects-lab.md#one-effect-three-visual-levels`: only the
close level pays for implicit geometry, while zoom compression remains
presentation-only and cannot affect simulation truth.