Explanation:

The IndexedFaceSet node represents a 3D shape formed by constructing faces (polygons) from vertices listed in the coord field. The coord field must contain a Coordinate node. IndexedFaceSet uses the indices in its coordIndex field to specify the polygonal faces. An index of -1 indicates that the current face has ended and the next one begins. The last face may (but does not have to be) followed by a -1. If the greatest index in the coordIndex field is N, then the Coordinate node must contain N+1 coordinates (indexed as 0-N). IndexedFaceSet is specified in the local coordinate system and is affected by parent transformations.