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### 3.6 Changing the Way Things Look

Geomview uses a hierarchy of appearances to control the way things look. An appearance is a specification of information about how something should be drawn. This can include many things such things as color, lighting, material properties, and more. Appearances work in a hierarchal manner: if a certain appearance property, for example face color, is not specified in a particular object's appearance, that object is drawn using that property from the parent appearance. If both the parent and the child appearance specify a property, the child's setting takes precedence unless the parent appearance is set to override.

Every geom in Geomview has an appearance associated with it. There is also an appearance associated with the "World" geom, which serves as the parent of each individual geom's appearance. Finally, there is a global "base" appearance, which is the parent of the World appearance.

The base appearance specifies reasonable values for all appearance information, and by default none of the other appearances specify anything, which means they inherit their values from the base appearance. This means that by default all objects are drawn using the base appearance.

If you change a certain appearance property for a geom, that property is used in drawing that geom. The parent appearance is used for any properties that you do not explicitly set.

Geomview has three panels which let you modify appearances.