KOF-222: Size mesh to geometry, not fixed defaults

[mkofler96]

Summary

Fixes KOF-222

The mesh size fields previously clamped to [0.5, 500] mm on every keystroke and started at a fixed 20 mm default. This made small parts unmeshable — a 1×1×1 mm cube could not be meshed at all because every legal setting was coarser than the part itself.

This PR removes the clamping, accepts any positive element size, and computes a fresh default for each import based on the geometry's volume and surface area, aiming at a target element count (50K). The suggestion is displayed alongside the model's bounding box and estimated element count, so users can make informed choices even with unbounded fields.

Key Changes

web/src/lib/meshSizing.ts (new)

• measureTessellation(): Computes volume (via divergence theorem), surface area, and bounding box of the tessellated geometry
• estimateElementCount(): Predicts Netgen's element count from a size using empirical coefficients (6 tets/h³ for volume, 2 triangles/h² for surface)
• sizeFromMeasure(): Inverts the estimator via geometric bisection to find the size that hits the target count
• suggestElementSizes(): Public entry point returning max/min size pair for a fresh import
• formatElementSize(): Rounds to 3 significant digits for readable display

web/src/hooks/useMesh.ts

• Changed maxElementSize and minElementSize from numbers to strings (no clamping on input)
• Added DEFAULT_MAX_ELEMENT_SIZE and DEFAULT_MIN_ELEMENT_SIZE constants for the initial UI state
• Added suggestion useMemo that recomputes when stepSurface changes (i.e., on import)
• Added useEffect to apply the suggestion to both fields on import
• Moved validation from input handlers to meshVolume(): checks that max is positive, min is non-negative, and min ≤ max
• Returns geometryMeasure from the suggestion so the UI can display extent and estimate

web/src/components/panel/MeshPanel.tsx

• Removed min/max/step attributes from the number inputs (fields now accept any positive value)
• Changed input handlers to store raw text, not clamped numbers
• Added geometry-extent section showing bounding box and estimated element count
• Added title attributes explaining the unbounded fields
• Added data-testid attributes for test selectors

web/src/components/panel/LeftPanel.module.css

• Added .hint class for the extent/estimate display (small monospace text in muted color)

web/src/workers/solver.worker.ts

• Moved validation of maxElementSize and minElementSize from the input layer to the worker entry point
• Added explicit error messages for non-positive max size, invalid min size, and min > max
• Clarified that any positive size is legal (KOF-222)

web/tests/mesh-size.spec.ts (new)

• E2E tests covering: sub-millimetre sizes can be typed and kept, fresh imports are sized to geometry, invalid sizes are rejected with specific messages, the worker rejects non-positive sizes, and a real import is meshed at its suggested size

web/tests/test_mesh_sizing.mjs (new)

• Unit tests for the estimator: measuring closed tessellations, empty geometry, hitting the target count across scales, the 1 mm cube case, scale invariance, open (surface-only) geometry, and error reporting for degenerate tessellations

Notable Implementation Details

• No clamping on input: The old Math.max(0.5, …) and Math.min(…, 500) are gone. Fields store raw text and are validated only when meshing starts, so users can type any value and see it reflected immediately.
• Geometry-driven defaults: Each import computes its own suggestion from volume and surface area. A 1 mm cube gets ~0.05 mm elements (10+ per side); a 2 m

https://claude.ai/code/session_01XCr53GMR7xYgA51rfjgn8U

[deepsource-io]

DeepSource Code Review

We reviewed changes in 303ba07...dce6328 on this pull request. Below is the summary for the review, and you can see the individual issues we found as inline review comments.

See full review on DeepSource ↗

PR Report Card

Overall Grade

Security   Reliability   Complexity   Hygiene   Coverage

Code Review Summary

Analyzer	Status	Updated (UTC)	Details
Code coverage		Aug 11, 2026 6:25p.m.	Review ↗
Rust		Aug 11, 2026 6:25p.m.	Review ↗
JavaScript		Aug 11, 2026 6:25p.m.	Review ↗
C & C++		Aug 11, 2026 6:25p.m.	Review ↗

Code Coverage Summary

Language	Line Coverage (New Code)	Line Coverage (Overall)
Aggregate	95.3%	88% [▲ up 0.2% from main]
Javascript	95.3%	88% [▲ up 0.2% from main]

➟ Additional coverage metrics may have been reported. See full coverage report ↗

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[deepsource-io]

use `Boolean((window as Window & { __kofem?: unknown }).__kofem)` instead

Prefer using explicit casts by calling Number, Boolean, or String over using operators like +, !! or "" +. This is considered best practice as it improves readability.

[deepsource-io]

Expected 'undefined' and instead saw 'void'

The void operator takes an operand and returns undefined. It can be used to ignore the value produced by an expression. However, this can lead to code that is difficult to understand and maintain. Historically, the void operator was used to get a "pure" undefined value, as the undefined variable was mutable prior to ES5.

[deepsource-io]

Block is redundant

In JavaScript, prior to ES6, standalone code blocks delimited by curly braces do not create a new scope and have no use. For example, these curly braces do nothing to foo: