element enables to switch on or off the object's visibility. This is a logical switch. When a new object is created, its visibility is on. Besides with objects, the visibility can also be changed with lights, thus enabling to switch the lights on or off. In complicated scenes the rendering speed may be increased by switching the visibility of hidden objects off. If e.g. the viewer is in one room, it is possible to increase the drawing speed by switching the visibility of objects situated in the next-door rooms off (The 3D system itself cannot recognize that some objects are hidden behind the wall). A suitable method is connecting
objects to the room. Thus, by switching the visibility of the hidden rooms off the visibility of all objects in the rooms, too, can be switched off. If a portion of a room is visible through an open door or window, then a division of the room in sectors visible from various positions may help and switching off the visibility of certain sectors (object groups found in the room) only.
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