Appearance { exposedField SFNode material NULL exposedField SFNode texture NULL exposedField SFNode textureTransform NULL }Explanation :
The Appearance node specifies the visual properties of geometry by defining the material and texture nodes. The value for each of the fields in this node can be NULL. However, if the field is non-NULL, it must contain one node of the appropriate type.
The material field, if specified, must contain a Material node. If the material field is NULL or unspecified, lighting is off (all lights are ignored during rendering of the object that references this Appearance) and the unlit object color is (0, 0, 0).
The texture field, if specified, must contain one of the various types of texture nodes (ImageTexture, MovieTexture, or PixelTexture). If the texture node is NULL or unspecified, the object that references this Appearance is not textured.
The textureTransform field, if specified, must contain a TextureTransform node. If the texture field is NULL or unspecified, or if the textureTransform is NULL or unspecified, the textureTransform field has no effect.