Zigzag engine (6802 lines, 184 tests):
- Construction 17 normalisation: working through dimension 3+
- Import from homotopy-rs JSON: working (scalar, two_scalars, half_braid)
- Piece extraction via Embedding/restrict_diagram: working
- Type checking pipeline: working (Eckmann-Hilton half_braid passes)
- Essential identity detection: validated with full 2-diagram test
Bugs found and fixed:
- assemble_factorisations losing cospan legs during reassembly
- RewriteN::slice() using source offsets instead of target indices
- singular_preimage() not handling passthrough heights
- restrict_rewrite() not accounting for accumulated cone offsets
- Embedding::preimage() using regular_preimage for Singular case
Added vis-engine-spec.md: visualization engine specification
- 6-layer architecture from math primitives to scene graph
- SVG renderer for 2D, WebGL2 for 3D, custom hit testing
- Spring constraint integration point for semiotic rendering
- No external dependencies - game engine approach
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
Added Point::is_visible() to explosion.rs:
- A point at geom_dim d is visible iff coords[d..] are all singular
- Matches homotopy.io's visibility filter (mesh.rs:111-115)
Updated render_braiding.rs:
- Filter to visible elements only (7 of 23 points for half_braid)
- Compute layout coordinates: x=time, y=height, z=depth
- Wires spread at z = [-1, 0, 1], vertices at z = [-0.5, 0.5]
- No volumes in output (not rendered)
Visible elements for half_braid:
- 2 vertices: (s0,s0,s0), (s1,s0,s0)
- 3 wires: (r0,s0,s0), (r1,s0,s0), (r2,s0,s0)
- 2 surfaces: (r0,r0,s0), (r0,r1,s0)
Updated web/zigzag-renderer.jsx with new geometry data.
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
Wire endpoints and surface boundaries require different computation methods:
- Wire endpoints: TRANSITIVE reachability to vertices
A strand spans between vertices even if poset path has intermediate points.
Most wires connect both v₀ and v₁; only wire 14 is a self-loop.
- Surface boundary_wires: DIRECT covering relations only
The immediate boundary of a surface is its direct predecessor/successor wires.
Surfaces have 1-3 boundary wires (was 1-7 with transitive).
Updated:
- examples/render_braiding.rs: restored reachable_from for wire endpoints
- fixtures/half_braid_geometry.json: correct wire endpoints + direct surface boundaries
- web/zigzag-renderer.jsx: updated embedded geometry data
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
