server/src/atlas/cascade.rs — run_cascade(body_seed, body_id, path,
default_sea_level, up_to) loads Layer 0 (heightmap.png) and runs every layer up
to the requested CascadeLayer, returning a CascadeSnapshot. The pure core
run_cascade_from_heightmap orchestrates the layers without file I/O (testable);
run_cascade is the thin path-loading wrapper.
CascadeSnapshot is extensible — each layer's artifact is an Option that becomes
Some once it runs (Layer 0 heightmap always present, Layer 1 topography next;
#954+ append their fields). The carried SeedChain is unused by the RNG-free
Layers 0-1 and feeds the RNG-using layers later (D-224). CascadeLayer is an
append-only ordered enum.
Tests: layer-gating, same-heightmap determinism, layer ordering. The golden-seed
regression fixture (the #952 deliverable) builds on this next.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
jpmschweitzerandClaude Opus 4.7
9bc2ed28f2