compute_biome receives absolute kelvin (the Whittaker table is kelvin; the
0-1 normalisation happens afterwards in simulate(), for the renderer only),
but two terrain rules compared it to 0.35. That was the case from the
generator's first commit (f84275edf):
- mountain rock, `temperature < 0.35`: never true, so the class never
appeared through this rule on any body;
- sulfuric scrub, `temperature > 0.35`: always true.
0.35 can only mean a fraction of the world's own range, the normalisation
compute_moisture already uses, so both rules now compare against that. A
world with no temperature range reads 0 (the cold end).
tooling/test_planet_biome_rules.py pins the rule both ways on a synthetic
body: cold high ground turns to rock (>90%, since anomaly scatter repaints
~3%), and warm high ground and low ground do not. Mutation-proven: restoring
the kelvin comparison fails it at a rock share of exactly 0.000. Wired into
make test-tooling.
Sulfuric scrub remains unreachable for a different reason: it converts rock
only at elev_norm 0.25-0.65, and rock exists only above 0.65. It is left as
found, since making it reachable is a design call and belongs to the balancing
pass, so it is not pinned.
Found while shaping the D-258 biome bake. The committed reliefmaps and globes
were rendered with the bug, and the coming bake reflects the fix.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
