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#### 3.6.3 The Lighting Panel

The Lights panel controls the number, position, and color of the light sources used in shading.

The Lighting Panel.

The Lighting panel is different from the Appearance and Material panels in that it always works with the base appearance. This is because it usually makes sense to use the same set of lights for drawing all objects in your scene.

LIGHTS
  The LIGHTS browser shows the currently selected light. Changes made using the other widgets on this panel apply to this light. There is always at least one light, the ambient light.
Intensity
  This slider controls the intensity of the current light.
Color
  This button brings up a color chooser which lets you select the color of the current light.
Add
  This button adds a light.
Delete
  This button deletes the current light.
Show Lights
  This button lets you see and change the positions of the light sources in a camera window. Each light is drawn as long cylinder which is supposed to remind you of a light beam. When you click on the Show Lights button Geomview goes into "light edit" mode, during which you can rotate current light by holding down the left mouse button and moving the mouse. Lights placed in this way are infinitely distant, so what you are changing is the angular position. Click on the Show Lights button again to return to the previous motion mode and to quit drawing the light beams.
Done
  This button dismisses the Lighting panel.

Geomview's Appearance, Materials, and Lighting panels are constructed to allow you to easily do most of the appearance related things that you might want to do. The appearance hierarchy that Geomview supports internally, however, is very complex and there are certain operations that you cannot do with the panels. The Geomview command language (GCL) provides complete support for appearance operations. In particular, the `merge-baseap` command can be used to change the base appearance (which, except for lighting, cannot be changed by Geomview's panels). The `merge-ap` command can be used to change an individual geom's appearance. Appearances can also be specified in OOGL files; for details, see Appearances. See `(merge-baseap ...)`. See `(merge-ap ...)`.