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JAX EvoGym

API Boundary

The stable public API is the square-cell JAX EvoGym core:

  • top-level voxel constants: EMPTY, RIGID, SOFT, H_ACT, V_ACT, FIXED, CONTRACTILE
  • world construction: EvoWorld, WorldObject, compile_world_template, compile_world_templates, instantiate_world
  • simulation/runtime types: SimState, PhysicsConstants, CollisionData, StaticColliderData, ActuatorInfo, PerAxisActuatorInfo, DeformationInfo, BuiltWorld
  • simulation helpers, built-in environments, rendering helpers, and the dense-grid JAX build path documented in this site

Compatibility-only surface

Section titled “Compatibility-only surface”

Some symbols remain importable because old fixtures and internal tests need to load or inspect them. These are not part of the stable release contract:

  • slope ids 7 through 30 in jax_evogym.constants
  • slope mirror/rotation/pairing tables
  • allow_experimental_slopes=True
  • slope_contact_* and slope_grip_* fields on PhysicsConstants
  • slope-only stiction scope

EvoWorld accepts known legacy slope ids so JSON fixtures can be loaded and inspected. Stable compilation rejects slopes by default.

Experimental slopes

Section titled “Experimental slopes”

Slopes are experimental geometry only. With allow_experimental_slopes=True, the builder may compile legacy slope cells into static polygon collider and render geometry. Sloped edges receive normal collision response, but tangential friction, stiction, near-contact support, slope grip, and persistent slope manifold behavior are disabled.

Slopes are left out of the designer palette, stable examples, and release gates because they still need a defensible friction/support model before they can be treated as research-library API.

Flat FIXED terrain is different: ground-plane friction, flat static-terrain tangential friction, and opt-in flat floor stiction are stable behavior.

JAX-side additions

Section titled “JAX-side additions”

Compared with original EvoGym, the stable JAX library adds:

  • object-separated world compilation instead of one merged grid
  • static fixed-terrain colliders omitted from SimState
  • CONTRACTILE per-axis actuation
  • deformation observations
  • pure-JAX dense-grid builders for vmap-heavy morphology search
  • ownership-aware rendering and the browser designer
  • documented damping/friction extensions for stable square-cell simulation