The Normal modifier allows you to unify or flip the normals of an object without applying an Edit Mesh modifier.
For example, if you wanted to fly inside of a procedural object, such as a sphere or a cylinder, and wanted to retain control over the radius and number of segments, you couldn't collapse the object to an Editable Mesh and maintain the procedural nature of the primitive.
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Flipping the normals of a sphere creates a sky dome over a city.
Patches
Patch objects coming up the modifier stack are not converted to a mesh by this modifier. A patch object input to the Material modifier retains its patch definition.
Procedures
To use the normal modifier:
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Select an object, then on the
Modify panel
Modifier List, choose Object-Space Modifiers
Normal.
The object appears to turn inside-out, since Flip Normals is on by default.
- If the object has some faces pointing inward and others outward, turn on Unify Normals to make all the faces point similarly. Tip: To flip or unify normals on part of an object, convert it to editable mesh and select faces or polygons. On the Surface Properties rollout in the Normals group, use the Flip and Unify buttons.
Interface
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- Unify Normals
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Unifies the normals of an object by flipping the normals so that they all point in the same direction, usually outward. This is useful for restoring an object's faces to their original orientations. Sometimes normals of scenes that have come into 3ds Max as part of a DWG or DXF file are irregular, depending on the methods used to create the scene. Use this option of the modifier to correct them.
Note: Unify Normals does not work on editable poly objects; before applying the Normal modifier, convert the model to editable mesh format or apply a Mesh Selector Turn To Mesh modifier. - Flip Normals
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Reverses the direction of all the surface normals of the faces of the selected object or objects. Default=on.