Level of Detail Utility

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, group them as one, and then run the Level Of Detail utility, which automatically creates a special LOD controller as a Visibility track. The LOD controller then hides and unhides the objects in the group, depending on their size in the rendered scene.

Utilities panel > Utilities rollout > More button > Utilities dialog > Level of Detail

The main purpose of this utility is to save time in rendering complex objects and in manipulating objects in the viewports. Since a portion of rendering speed is directly related to the number of faces that must be rendered in a scene, using the Level Of Detail utility lets you reduce the number of rendered faces as an object reduces its apparent size. In addition, you can use this utility to display a simple stand-in for a more complex object in the viewports. Since the stack is not calculated for objects hidden in the viewports, you can speed up viewport manipulation by using this utility to substitute complex stack objects with simple stand-ins.

Procedures

To set up an object for the Level Of Detail utility:

Create two or more objects that are identical except for their complexity.
Note: It's best to assign materials and mapping coordinates, as well as all modifiers while the objects are still separate.
Select all of the objects, and use the Align tool to center all of them about a common center.
Group the objects.
Choose the Level Of Detail utility.
While the grouped object is selected, click the Create New Set button.
The name of the objects within the group appear in the Level Of Detail list, in order of complexity; only the least complex object in the group is displayed in the viewports, while all other objects are made invisible.
Use the controls in the Level Of Detail rollout to adjust when the objects will switch their display in the rendered scene.

To access an object's stack:

Select the Level Of Detail object, and then choose Group menu Open.
In the Level Of Detail utility, choose the object you want to access from the list window, and then turn on Display In Viewports (or double-click the object's name in the list window).
Select the object in the viewport.
Open the Modify panel to access that object's parameters.
When finished, choose Group menu Close.

To assign materials within the group:

Select the grouped object.
Use Display In Viewports in the Level Of Detail utility to display the grouped object you want to assign the material to.
Drag the material from the Material Editor (or the Browser) over to the object in the viewport.
Choose Assign To Object in the Assign Material alert, and then click OK.
Note: Be sure and choose Assign To Object. If you choose the default Assign To Selection, all objects in the group will be assigned the same material.

To dismantle a Level Of Detail object:

If you look at a Level Of Detail object in Track View, you'll see only the tracks for the sub-object that's currently displayed in the viewports. To see all sub-objects in Track View, you need to turn off Visible Objects.

If you need to dismantle a grouped Level Of Detail object, and restore its sub-objects to their independent states, follow these steps:

Open the Filters dialog in Track View, and turn off Visible Objects in the Show Only group box.
The tracks for all of the sub-objects in the Level Of Detail object are now visible.
Open the hierarchy of each of the sub-objects, and then select each of their Visibility tracks.
On the Track View toolbar, click the Delete Controller button.
If you also want to remove the grouping, select the grouped objects, and then choose Explode in the Group menu.

Interface

Level of Detail Set group

Lets you create a new set, and add or remove objects from the current set.

Create New Set: Creates a new Level of Detail set based on a currently selected group object.
Add To Set: Adds an object to the Level of Detail set. You must first attach the object you want to add to the group object. To add an object to the set, use Align to center the object with the group object. Select the object you want to add, and then choose Attach from the Group menu, and then click the group object. Finally, click the Add to Set button, and then click the object you want added.
Remove from Set: Removes the object highlighted in the list window from the current set. Note that the object then becomes visible in the viewports, but is still part of the group. To remove the object from the group, choose Group menu Open, select the object you want removed, and choose Group menu Detach. Select the group object again, and choose Group menu Close.

Image Output Size group

Width/Height: The Width and Height spinners in this area are set to the current rendering output size each time you enter the Level of Detail utility. Using the spinners, you can change this to any resolution. If the percent of Target Image option is selected, as you change the Target Image Size, the threshold values change as well.
Reset to Current: Resets both spinners to the current rendering output size.

[list window]: Lists all of the objects in the group by complexity, with the least complex at the top of the list. The numbers at the left of each object name are the threshold values that indicate at what size the object will be displayed in the rendered scene. The numbers can be one of two types of units, pixels, or percentage of the target image. You set the type of unit in the Threshold Units group.
Display in Viewports: Displays in the viewport the object highlighted in the list window. Only one object in the group is displayed in the viewports at any time. As a default, the least complex object is displayed, but you can look at the other objects by highlighting them in the list and selecting this item. Double-clicking the object name in the list performs the same function.

Threshold Units group

The options in this group box let you choose between two types of threshold units. Switching between these two options does not alter the effect; it alters the method by which you set the thresholds.

Pixels The thresholds are determined by specifying the maximum pixel size of the image (measured diagonally). Use when you want to set the transfer thresholds using absolute rather than relative values.
% of Target Image Sets the thresholds based on the percentage of the size of the image (measured diagonally) relative to the size of the rendered output.

Thresholds group

Min Size/Max Size: Sets the minimum size of the object before it's replaced by the less complex object, and the maximum size of the object before it's replaced by the more complex object. The values vary depending on the current type of Threshold Unit. The default threshold values are initialized so that the most complex object is 100 percent of the image output size. The remaining thresholds are set using an algorithm based on a ratio of the number of faces between each object. It assumes that all faces are the same size, and then picks thresholds so that the faces would remain a constant size as displayed on the screen. Usually, this will provide the type of smooth transition you need, but you can customize the threshold values. The threshold values are interrelated between the objects, so altering the minimum size of one object, for example, will also alter the maximum size of the next object.
Reset All: Resets all thresholds for all objects in the list, using the previously described algorithm.

Tip: You can use the Level of Detail utility to create objects that display very simple geometry in the viewports, while displaying complex geometry in the rendered scene. Create a grouped Level of Detail object consisting of only two objects, the complex object and the simple object. Select the simple object in the list window and, in the Thresholds are, set its Min Size and its Max Size to 0. This will display the simple object in the viewports, but the complex object will always appear in the rendered scene, regardless of its apparent size.

Close: Closes the utility.