A 3D world boundary shape, intended for use in physics. [WorldBoundaryShape3D] works like an infinite plane that forces all physics bodies to stay above it. The [member plane]'s normal determines which direction is considered as "above" and in the editor, the line over the plane represents this direction. It can for example be used for endless flat floors.
[b]Note:[/b] When the physics engine is set to [b]Jolt Physics[/b] in the project settings ([member ProjectSettings.physics/3d/physics_engine]), [WorldBoundaryShape3D] has a finite size (centered at the world origin). It can be adjusted by changing [member ProjectSettings.physics/jolt_physics_3d/limits/world_boundary_shape_size].