The concentric banding persisted on the jets (near the base) after the
disk moiré was fixed. Root cause: sample_jets used a fixed per-step
weight (0.5) instead of a per-unit-length one, so the jet's
per-unit-length contribution was ∝ 1/step_len. RK45 packs its accepted
steps tightly near the hole (high curvature → small dt), so the jet
brightened in step-dense rings exactly where the user saw bands. This
was the inverse of the earlier `* dt` attempt (which banded because dt
varies 16×); both forms couple brightness to the integrator's step
choice rather than to the physics.
Fix: pass the step's world-space length |new_pos − prev| in from the
caller (it already has prev and new_pos) and weight the per-step
emission and alpha on it — the same step-size-decoupling technique the
disk path already uses (integrate_disk_segment's analytic seg_len). The
per-unit-length coefficient (0.1) is calibrated to keep the default
scene's jet brightness close to the old fixed-0.5 look.
cargo build --release: clean. cargo test: passing.
xfy
573e68e96d