From BlenderWiki
NormalEdit Modifier
This modifier creates or modifies a custom split normals data layer.
Common Options
- Mix Mode
- How to affect (use) existing normals. Note if you chose 'COPY' and set Mix Factor to 1.0, you completely overwrite existing normals.
- Mix Factor
- How much new normals affect existing ones.
- Vertex Group
- Which vertices’ normals are affected - weights of 1.0 will get full new normals, weights of 0.0, full org normals, values in between will result in normals interpolation. Note you can invert the group’s influence.
Radial Mode
This is the simplest option, it sets normals per vertex, using the value they would have if they were on the surface of an ellipsoid. By default, the center of the ellipsoid is the center of the modified object, and its dimensions are those of its bounding box. Commonly used to 'shade' low-poly bushes or trees (in game world).
- Target Object
- When set, the target object will define both center and dimensions of the ellipsoid (through its scale only, not its geometry if it has one).
- Offset
- If no target object is set, allows to define an offset from modified object's center, as center of the ellipsoid.
Directional Mode
Just makes all normals to point toward given target.
- Target Object
- Mandatory, generated normals will point towards that object's center.
- Parallel Normals
- If set, all generated normals will be parallel to the line between modified's and target's centers.
- Offset
- When Parallel Normals is set, allows to offset from modified object's center.
