The stratum corneum is modelled as flattened corneocyte "bricks" stacked in overlapping rows. The cells themselves are essentially impermeable — everything that moves through the skin surface has to squeeze through the lipid "mortar" filling the seams between them.
Every mortar seam has a fixed weak point. Dragging integrity down doesn't add randomness each frame — it erodes seams whose weak point falls below the current damage level, so the same slider value always produces the same gap pattern.
- Blue dots are water molecules diffusing up from the moist dermis. An intact seam forces a slow, tortuous path — a gapped one is a straight highway out, which is exactly what "increased TEWL" means.
- Orange dots are irritant/allergen particles pressing in from outside. The same seams that leak water out let them punch in — the two failures share one cause.
- TEWL rate and penetration rate are both derived from the same per-seam permeability field, so they rise together as integrity falls — the barrier's two jobs (keep water in, keep irritants out) degrade as one.