You can associate a background with a viewport by calling its setBackground() member function. Remove a previously set background by calling this function with a NULL argument. You can apply a gradient, image, or solid background to the viewport using the AcDbBackground-derived classes. The sun and sky backgrounds also appear in AutoCAD, and use the AcDbSkyBacground derived class. The sky background is a procedurally generated image of a natural sky dome.
The override property enables you to disable the sky background and enable the previous background when you switch back. The background can be enabled or disabled through view or visual styles.