POV-Ray : Documentation : Normal Maps and Normal Lists
  POV-Ray 3.6 Documentation Online View Slope Maps Bump Maps Normal Maps and Normal Lists

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_BODY }
    [ 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: that 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.

There may be from 2 to 256 entries in the map.

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 {
    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. Slope Maps Bump Maps

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