Add Visibility Track controls when you can see an object. Visibility tracks can only be added to objects.
You can create a visibility track by either animating the Visibility parameter on the Object Properties dialog or by selecting an object in the Track View Hierarchy and clicking Tracks menu Visibility Tracks Add. In both cases a visibility track, using a Bezier float controller, is created in Track View. The visibility track displays as a child of the object in the Track View Hierarchy.
When you first assign a visibility track to an object, a Bezier float controller is automatically assigned; this allows visibility to change over the course of the animation. You can make an object appear or disappear suddenly by changing the interpolation of the visibility keys to Step tangency or with the On/Off controller.
Variable opacity is supported in the shaded viewports. For ease of use, the object never completely disappears from the viewports.
An object can inherit the visibility of its parent (as determined by the parent's Visibility track in the Track View). Use the Object Properties Inherit Visibility check box to specify the visibility inheritance of an object.
All members of a Group inherit the visibility of the parent when a visibility controller is assigned to the parent. Transparent materials and hidden objects have no effect on this function.
Level of Detail Utility and Visibility
The Level of Detail utility lets you construct an object that alters its geometric complexity or level of detail based on its size in the rendered image. You create several versions of the same object each with different levels of detail; you group them as one, and then assign the Level of Detail utility. This automatically creates a special LOD controller as a Visibility track.
To add a visibility track to objects:
A value of 0 creates an invisible object, a value of 1.0 creates a fully visible object. Change the interpolation to step for sudden visibility, rather than gradual fades.
A visibility track appears below the selected object(s). Add and edit keys in the visibility track to control the object's visibility.
Example: To create and animate a visibility track using the Object Properties dialog:
This creates a visibility track in Track View and adds a key with a value of 0 to the track.