Function show 

pub(crate) fn show(
    world: &mut World,
    instance: RenderEntity,
    mesh: RenderEntity,
    material: RenderEntity,
    transform: &Transform,
) -> bool

Show one instance: point it at a mesh and material, place it, and make it visible.

A frame’s show is a request the gameplay world asked for, so it answers by the ball it was asked for rather than publishing into a stream: the caller names what it asked for and learns whether it happened. An instance that is gone, or assets that never landed, answers false, which is the difference between a world that has not answered and one that answered no.