Function default_instance 

fn default_instance(device: &Device) -> Buffer

Available on crate feature egui only.

A one-element buffer holding the identity MeshInstance.

The built-in lit pipeline declares the instance stream for every variant, so a draw that binds nothing at INSTANCE_SLOT is rejected. A UI draw reads no instance state — its vertices are already in screen space — so one default record satisfies the slot for every draw the integration records.