The input model
Every frame, a provider hands you an array of InputSourceSnapshot objects, one per live input source. A source is a controller, a hand, gaze or a 2D pointer such as a mouse, normalised into the same shape whatever produced it. Fields a provider cannot supply are simply absent from a snapshot, so a consumer gates behaviour on capabilities rather than on checking for a field every frame. See Capabilities and negotiation for that gating.
Identity fields
id is a stable string per session, such as "left-hand" or "right-controller", but its exact format is not part of the contract. Never parse it: read handedness for the side an input source belongs to instead. kind says what kind of physical thing produced the source: "controller", "hand", "gaze", "pointer2d" or "other". handedness is "left", "right" or "none", the last for sources with no side, such as a mouse.
Pose and geometry
ray is the pointing ray, a RayTuple of a world-space origin and a normalised direction. It carries the target ray, hand ray, gaze ray or a projected 2D pointer, depending on kind. gripPose is the grip or palm pose, a PoseTuple of a Vec3Tuple position and a QuatTuple orientation. indexTip is the index fingertip's world position, a plain Vec3Tuple, useful for poke and hand-driven behaviours.
Geometry is plain data throughout, with no engine types anywhere: Vec3Tuple is [x, y, z] in metres, QuatTuple is [x, y, z, w], and PoseTuple and RayTuple combine them. HeadPose has the same position/quaternion shape and is the viewer pose, a camera on desktop and the headset in an XR session.
Select, squeeze and grab
select and squeeze are 0 to 1 scalars: the primary action (trigger, pinch strength, mouse button) and the secondary action (grip button). Consumers that need a boolean from a scalar use the shared hysteresis thresholds, SELECT_PRESS_THRESHOLD (0.7) and SELECT_RELEASE_THRESHOLD (0.3), so a value has to cross a higher bar to register a press than to release one. nativeGrabbing is a boolean flag that is true while the engine itself reports this source natively grabbing something, such as an IWSDK grabbable under physics. hapticsAvailable reports whether this specific source can take a haptic pulse; the provider-level capabilities.haptics says whether any source can.
Velocity
linearVelocity and angularVelocity are optional Vec3Tuples on the grip: metres per second, and a rotation axis scaled by radians per second. A provider fills them when its engine reports velocity natively, and a consumer can derive them from two consecutive grip poses otherwise. See Pointer streams and velocity for velocityBetween, the helper that does the deriving.
Ownership
A snapshot, and every tuple inside it, belongs to whoever sample() handed it over to. A provider builds fresh objects on each call and never writes to a snapshot it has already returned, so a consumer may keep one across frames, such as last frame's grip pose for a velocity tracker, without copying it defensively. A provider that pools objects internally must copy on hand-over rather than refill the same object in place. The conformance suite checks this rule; see Provider conformance.