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Skill: refinement=R is a factor on the background spacing, not a grading ratio - #580

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Skill: refinement=R is a factor on the background spacing, not a grading ratio#580
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@lmoresi lmoresi commented Aug 16, 2026

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The adaptive-meshing skill described refinement=R as the finest:coarsest cell-size ratio.

It is the maximum local refinement on the background cell size h0. The metric targets the envelope h ∈ [h0/R, h0·coarsening], and coarsening="auto" takes the budget-conserving R**(1/d). The realised finest:coarsest ratio is R**(1+1/d) — about 11 for R=5 in 2-D and 8.5 in 3-D, not 5.

Source of truth: metric_density_from_gradient in src/underworld3/meshing/smoothing/metrics.py.

The skill is the first thing a session reads about the mover, so anyone sizing a mesh from it was asking for roughly twice the grading they thought. Also records that passing refinement takes the envelope branch, which ignores amp, lo/hi_percentile, mode and power.

Underworld development team with AI support from Claude Code

…ing ratio

The adaptive-meshing skill described refinement=R as the finest:coarsest
cell-size ratio. It is the maximum local refinement on the background spacing
h0: the metric targets h in [h0/R, h0*coarsening], and coarsening="auto" takes
the budget-conserving R**(1/d). The finest:coarsest ratio is therefore
R**(1+1/d) — about 11 for R=5 in 2-D, not 5.

The skill is the first thing a session reads about the mover, so the error
propagated into every model built from it. Also records that passing refinement
takes the envelope branch, which ignores amp, lo/hi_percentile, mode and power.

Underworld development team with AI support from Claude Code
Copilot AI lite review requested due to automatic review settings August 16, 2026 07:54

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