# Normal Details

## Overview

A normal is line that is perpendicular to the plane of a triangle. The normal is used to perform lighting reflection calculations and determine whether a triangle faces toward the camera or away from the camera.

If faces are connected to each other, the normals can be averaged to make the edges where they connect appear smooth. You cannot directly manipulate a face's normal, but you can influence the averaging calculations by assigning faces to a group and then changing the group properties. See the Group Window for details.

You can invert the normals of selected faces using the Invert Normals command. If some or all normals in a mesh are facing the wrong direction (pointing inward) and the faces are part of an enclosed mesh, you can use the Normals Face Out command to make all normals point outward. If the triangles are not part of an enclosed mesh the behavior is undefined.

## See Also

- Faces
- Meshes
- Groups