Scenario and Scene

A Scenario is the reproducible input boundary for an application. Scene is the portion FastSim Core understands to construct the physical world; the terms are not interchangeable.

Three Scenario regions

Region	Owner	Purpose
`scene`	FastSim Core	Environments, entities, sensors, lights, and initial physical declarations
`behavior`	Selected plugins	Private tasks, goals, policies, or workflow inputs
`evaluation`	Selected plugins	Private success conditions and evaluation inputs

Core resolves, normalizes, and locks all three, but interprets only Scene. A plugin may read behavior or evaluation only when its Manifest requests the corresponding scope.

Scene entity groups

Scene organizes environment, objects, articulations, robots, deformables, fluids, sensors, and lights under stable entity IDs. Each instance selects a component and supplies per-run pose, parameters, and bindings.

A component Manifest defines what an asset is; Scene defines where and how it is instantiated. Shared assets therefore do not accumulate run-specific poses.

Compiled and live views

ScenarioPlan is the immutable compiled projection. Live Scene Query returns catalog, state, and delta values: catalog describes structure, state reports one generation/revision, and deltas report later changes.

Plugins should rely on FastSim entity, link, joint, and frame identities instead of native Prim paths or object addresses. See Scenario configuration and the Python Scene API.