Shape { exposedField SFNode appearance NULL exposedField SFNode geometry NULL }Explanation :
The Shape node has two fields, appearance and geometry, which are used to create rendered objects in the world. The appearance field specifies an Appearance node that specifies the visual attributes (e. g., material and texture) to be applied to the geometry. The geometry field specifies a geometry node. The specified geometry node is rendered with the specified appearance nodes applied.
If the geometry field is NULL, the object is not drawn.