Floating Origin

Orbital distances are enormous — low Earth orbit is roughly 400 km altitude, geostationary orbit is ~36,000 km. Bevy (and most game engines) use 32-bit floats for world-space transforms, which have insufficient precision at these scales.

How it works

The floating origin pattern keeps the Bevy world origin near the camera target at all times. Each frame:

1. The floating_origin system (in PostUpdate) measures the offset between the current world origin and the active CameraTarget's position.
2. If the offset exceeds MAX_ORIGIN_OFFSET, all entity Transform positions are shifted — the world is "recentred" around the target.
3. Because the offset is subtracted from every entity uniformly, relative positions are preserved.

This means that even though real distances are millions of metres, no entity's Bevy Transform ever drifts far from the origin, keeping floating-point precision acceptable.

Relevant constants

Constant	Description
PHYSICS_ENABLE_RADIUS	Entities within this distance (double precision, metres) have Avian3D physics enabled
PHYSICS_DISABLE_RADIUS	Entities beyond this distance have physics suspended (RigidBodyDisabled)
MAX_ORIGIN_OFFSET	Maximum allowable offset before a floating origin correction is applied
MAX_LINVEL	Linear velocity cap applied to physics bodies to prevent instability during origin shifts

Interaction with physics

Avian3D physics bodies store positions internally in double precision. When the floating origin shifts, the floating_origin system also updates Avian3D's Position component (not just the Bevy Transform) to keep physics and rendering consistent.

Interaction with the camera

orbit_camera_track is ordered after floating_origin (.after(floating_origin)) so that the camera transform is computed using the post-shift world positions, preventing a one-frame lag artefact.