get geometry() {
    return getSphereGeometry(this.detail)
  }
A simple sphere, centered on the origin.
The `radius` property is an alias to the uniform `scale`. Set `scaleX/Y/Z` individually if
you need non-uniform scaling.
The `detail` property allows selecting a LOD; its values can be 'low', 'medium', or 'high'.
To control the material, see {@link MeshFacade}.