The Groups Window is used to add or remove model groups (collections of faces) You may also set which faces are in which groups and assign textures. Select Edit Groups from the Main Window's Materials menu.
The combo box at the top of the window contains the names of all groups in this model. You can select a group name and use the face assignment buttons (Assign As Group and Add To Group) to set which faces belong in this group. You may also use the Select Faces In Group button to select the faces that belong to the group (this will clear any selected vertices and faces) and the Unselect Faces In Group button to unselect (other selected faces and vertices will remain selected).
To add a new group click the New button and enter a name (names do not need to be unique, though duplicate names may be confusing for other people using this model). The name is limited to 31 characters. To remove a group from the model, select the group name in the combo box and click the Delete button. Note that deleting a group in this window does not delete any faces that are in the group. This only deletes the group name. To rename a group click the Rename button.
The Smoothness slider allows you to change how smooth the surface of the polygons of the group appear (this does not change the position of vertices, it only affects the normals used for lighting calculations). A smoothness of 0 will show all the polygons as flat polygons. A smoothness of 100 will make the polygons appear as smooth as possible in viewports with smooth polygon shading enabled.
The Max Angle slider allows you to change specify the maximum angle that will automatically be smoothed. Faces that share an edge at an angle greater than this angle will be drawn as a sharp edge. Faces that share an edge at an angle less than this angle will be drawn as a rounded edge (this does not change the position of vertices, it only affects the normals used for lighting calculations).
To assign a texture to a group, select the group name in the group combo box and select a texture name in the texture combo box. A preview of the texture image will be displayed in the frame below the texture combo box. You can also use the Group Properties panel to assign a material to a group without opening the Groups Window.
Press Ok to keep your changes or press Cancel to ignore any changes.