Note that attaching a normal pattern does not really modify the surface. It only affects the way light reflects or refracts at the surface so that it looks bumpy. Each of the items in a normal are optional but if they are present they should be in the order shown above to insure that the results are as expected. If no identifier is specified then the items modify the normal values in the current default texture. Typical values range from 0.0 to 1.0 but any value may be used.
Negative values invert the pattern.
The default value if none is specified is 0.5. Such modifiers apply only to the normal and not to other parts of the texture. Modifiers should be specified last. They are pattern normals, specialized normals and bump maps. They differ in the types of modifiers you may use with them.