Reference:Normal Map

Most of the time you will apply single normal pattern to an entire surface but you may also create a pattern or blend of normals using a normal_map. The syntax for a normal_map is identical to a pigment_map except you specify a normal in each map entry. The syntax for normal_map is as follows:

NORMAL_MAP:
  normal_map { NORMAL_MAP_BODY }
NORMAL_MAP_BODY:
  NORMAL_MAP_IDENTIFIER | NORMAL_MAP_ENTRY...
NORMAL_MAP_ENTRY:
  [ Value NORMAL_BODY ]

Where Value is a float value between 0.0 and 1.0 inclusive and each NORMAL_BODY is anything which can be inside a normal{...} statement. The normal keyword and {} braces need not be specified.

Note: The [] brackets are part of the actual NORMAL_MAP_ENTRY. They are not notational symbols denoting optional parts. The brackets surround each entry in the normal map.

In previous versions there had to be from 2 to 256 entries in the map. A Change in version 3.8 has removed the upper restriction.

For example:

normal {
  gradient x       //this is the PATTERN_TYPE
  normal_map {
    [0.3  bumps scale 2]
    [0.3  dents]
    [0.6  dents]
    [0.9  marble turbulence 1]
    }
  }

When the gradient x function returns values from 0.0 to 0.3 then the scaled bumps normal is used. From 0.3 to 0.6 dents pattern is used. From 0.6 up to 0.9 a blend of dents and a turbulent marble is used. From 0.9 on up only the turbulent marble is used.

Normal maps may be nested to any level of complexity you desire. The normals in a map may have slope maps or normal maps or any type of normal you want.

A normal map is also used with the average normal type. See Average for details.

Entire normals in a normal list may also be used with the block patterns such as checker, hexagon and brick. For example:

normal {
  checker
  normal { gradient x scale .2 }
  normal { gradient y scale .2 }
  }

Note: In the case of block patterns the normal wrapping is required around the normal information.

You may not use normal_map or individual normals with a bump_map. See section Texture Maps for an alternative way to do this.

You may declare and use normal map identifiers but the only way to declare a normal block pattern list is to declare a normal identifier for the entire normal.