Fields and disturbances

Draft

This page is scaffolded. The outline below marks what it should cover.

Each Field is a single concrete physical kind (GravityField, FluidField, MagField, CollisionField, OpticalField). Per-source variation is expressed by attaching different Disturbance subclasses to the same field instance.

To cover

• One field per physical kind — why GravityField is a single class and a planet's pull, a uniform background, and a body-pull are all disturbances on it.
• Combining — most fields are a plain linear superposition (sum) of their disturbances (gravity, B-field). FluidField is richer: each disturbance has a combining role and a smooth spatial membership, and the field folds them per FluidField.value_at_sym:
  • "baseline" — a regime medium (Ocean, Atmosphere) that layers by membership in insertion order (base ← (1−w)·base + w·value), so a background overlaid by a pocket is an alpha-composite override — density is selected by region, never summed.
  • "averaged" — a membership-weighted self-mean among the averaged disturbances (overlapping wind bubbles agree on the mean).
  • "additive" — a membership-weighted perturbation summed on top (currents, thruster wakes, explosions).
• Estimable disturbances — how a disturbance carrying State/Noise (e.g. CraftWindBubble) becomes a state the EKF estimates.
• Body-anchored disturbances — sources that ride a craft via a FieldSource part.

Source material

• Reference: Fields
• Code: manta/fields/base.py (combining logic), manta/fields/*.py