nox-py Development

nox-py is the Elodin Python SDK — PyO3 bindings that bridge Python simulations to the Rust ECS engine (in nox-py/src/), the NOX tensor compiler (→ cranelift / JAX), and Impeller telemetry.

Build & Test

just install py

# Run tests
pytest libs/nox-py/tests/

# Quick verification with an example
elodin editor examples/three-body/main.py

Rebuild the wheel after any Rust changes. Python-only changes in python/elodin/ are picked up immediately.

Architecture

Python user code
    │
    ▼
python/elodin/__init__.py    ← Python API surface, decorators, Query/GraphQuery
    │
    ▼
libs/nox-py/src/lib.rs       ← PyO3 module registration
    │
    ├── world_builder.rs      ← World creation, spawn, run
    ├── system.rs             ← System compilation pipeline
    ├── component.rs          ← Component types and metadata
    ├── archetype.rs          ← Archetype definitions
    ├── query.rs              ← Query system (map, map_seq)
    ├── graph.rs              ← GraphQuery and edge_fold
    ├── spatial.rs            ← SpatialTransform, SpatialMotion, SpatialForce, SpatialInertia
    ├── entity.rs             ← EntityId management
    ├── exec.rs               ← WorldExec enum (Iree/Jax), profiling, DB integration
    ├── jax_exec.rs           ← JaxExec, JaxWorldExec (JAX JIT per-tick execution)
    ├── step_context.rs       ← StepContext for pre/post step callbacks
    ├── impeller_client.rs    ← Impeller client for DB connection
    ├── asset.rs              ← Mesh, Material, GLB asset handling
    ├── linalg.rs             ← Linear algebra utilities
    ├── ukf.rs                ← Unscented Kalman Filter
    ├── s10.rs                ← S10 recipe integration
    └── error.rs              ← Error types and Python exception mapping
    │
    ▼
libs/nox/                     ← Tensor library, symbolic backend
    │
    ▼
libs/cranelift-mlir/          ← Pure Rust StableHLO runtime

Python API Surface

python/elodin/__init__.py

The main API module. Exports:

• Decorators: @system, @map, @map_seq
• Types: World, Query, GraphQuery, Component, Archetype, Body
• Spatial types: SpatialTransform, SpatialMotion, SpatialForce, SpatialInertia, Quaternion
• Built-in components: WorldPos, WorldVel, Inertia, Force, WorldAccel
• Utilities: six_dof(), Panel, GraphEntity, Mesh, Material, Edge

python/elodin/jaxsim.py

JAX-only execution mode. Compiles the simulation world into pure JAX functions for RL training and jax.vmap batching.

python/elodin/egm08.py / python/elodin/j2.py

Earth gravity models. EGM08 is a high-fidelity spherical harmonics model; J2 is simple oblate Earth.

Key Rust Modules

world_builder.rs

Central orchestrator. Handles World.spawn(), World.insert(), World.run(), World.build(), World.to_jax(). This is where simulation execution modes branch.

system.rs

Compiles Python-defined systems into executable computations via cranelift (default) or JAX. Handles the @system, @map, @map_seq decorator logic on the Rust side. System composition (pipe |) is implemented here.

exec.rs

Defines WorldExec enum with Cranelift(CraneliftWorldExec) and Jax(JaxWorldExec) variants. Both implement the same interface for tick execution, profiling, and DB integration. The backend parameter in w.run() / w.build() selects between the cranelift and JAX execution modes.

jax_exec.rs

JAX backend: compiles Noxpr graph → jax.jit() callable, then executes each tick by calling the JAX function via PyO3. Slower than cranelift but supports all JAX operations and the GPU.

component.rs

Maps Python Component annotations to component schemas. Handles type inference, metadata, and the ComponentType / PrimitiveType hierarchy.

spatial.rs

PyO3 bindings for spatial vector algebra types. Each type wraps a nox tensor and exposes Python-friendly constructors, accessors, and arithmetic operators.

graph.rs

Graph query implementation. edge_fold is the core operation — it iterates edges, queries left/right entity components, and accumulates results.

Adding a New Feature

New Component Type

1. Define the Rust type in component.rs or a new module
2. Add PyO3 #[pyclass] bindings
3. Export in lib.rs module registration
4. Add Python-side type alias in python/elodin/__init__.py
5. Test: spawn an entity with the component, verify it appears in the editor

New System Decorator

1. Implement the Rust compilation logic in system.rs
2. Add the Python decorator in python/elodin/__init__.py
3. Ensure it composes with | (pipe operator)
4. Test: write a simulation using the new decorator, verify output

New Execution Mode

1. Add the mode in exec.rs (or world_builder.rs for world-level API)
2. Wire CLI support in apps/elodin/ if needed
3. Add Python API in world_builder.rs

Dependencies

Key References

• Full SDK documentation: libs/nox-py/README.md
• Python API reference: docs/public/content/reference/python-api.md
• nox-py Rust source: libs/nox-py/src/
• Impeller protocol: libs/impeller/