Normal Map of sphere

Normal maps are images that store normals directly in the RGB values of an image. It's a popular method in 3d games and render software to achieve very realistic mapping of fake 3d reliefs.

 

Normal maps in Blender store a normal as follows:

Red maps from (0-255) to X (-1.0 - 1.0)

Green maps from (0-255) to Y (-1.0 - 1.0)

Blue maps from (0-255) to Z (0.0 - 1.0)

 

Since normals all point towards a viewer, negative values are not stored. In Blender we store a full blue range, although some other implementations also map blue colors (128-255) to (0.0 - 1.0). The latter convention is used in "Doom 3" for example.

 

Relief sample, rendered with AO (also nice to use as Color Map)
Normal Map of the above relief.

Creating Normal Maps

Creating normal maps in Blender is very easy. Just use the "Nor" as "Map Input", and use a Blend texture to define the gradient. Copy this to three texture channels, and set the coordinates for mapping appropriate to only map X, Y or Z.

For highest resolution you can also force the Blue component (Z) to only map to positive values.

 

A sample .blend file with such a Material can be downloaded here.

 

Don't forget to render such maps with an Ortho camera, to get the widest range of normals, and no perspective distortion.

 

Settings for creating a normal map. From left to right:

 

  1. Create 3 channels with default Blend texture (horizontal)
  2. Since this is the 2nd channel, map the Y coordinate (of normal) to the X (for the Blend)
  3. Choose "Nor" as texture coordinates to use
  4. Make the Map Input generate a green color
  5. Make sure the color is Added to the previous channel

Using Normal Maps

Using Normal Maps is as simple as setting the "Normal map" button in the Image Panel in the Texture buttons, and make sure you apply this in the Material buttons "Map To" panel on "Nor".

 

The picture below uses the Normal Map and Color Map from the relief as rendered above. Note that this is just a rendering of a flat plane!

 

Since only the normals get affected during render, you will not get shadow or AO or other '3D' effects. It's still just a texture.

Normal Map and Color Map created with the steps above applied to a plane

Todo For Next Release

Officially the 2.36 release was for fixes only, but we couldn't resist to at least "fix" this in Blender.

It is imortant to note that the current support for normal maps isn't finished still. Two important additions can be expected in a new release;

 

  1. "Object space" versus "Tangent space":
    By only storing the normals in a map with a positive Z component, you can also wrap them around a model, where the map-normals will be applied (rotated) according to the orientation of the face. Although Blender uses and creates such "Tangent maps", it currently doesn't apply it using "tangent mapping". Current mapping is to "Object space" only.

    Meaning: normal maps in Blender now only render correct when applied on a flat plane

    Note: there also exist normal maps storing all normals (also with negative Z) based on Object Space. Creating such maps is quite difficult though, certainly in Blender.

  2. Allowing "Parallax Mapping":
    Although we added texture "warping" (see the texture page ) this is different from what you can achieve with "Parallax Mapping". That latter is a texture coordinate deform based on moving the texture as if there's a height field applied. This can be used for any texture in Blender, not only for normal maps.

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