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 do this by creating several versions of the same object each with different levels of detail, grouping them as one, and then assigning the Level of Detail utility, which automatically creates a special LOD controller as a Visibility track. The LOD controller then hides and unhides the various objects in the group, depending on their size in the rendered scene.
The main purpose of this utility is to save time both 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.
Lets you create a new set, and add or remove objects from the current set.
Create New Set: Click this to create a new Level of Detail set based on a currently selected group object.
Add To Set: Click this to add an object to the Level-of-Detail set. To do this, 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 Open in the Group menu, select the object you want removed, and choose Detach in the Group menu. Finally, select the group object again, and choose Close in the Group menu.
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 % of Target Image option is selected (below), as you change the Target Image Size, the threshold values change as well.
Reset to Current: Click this to reset 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 unitspixels, or percentage of the target image. You set the type of unit in the Threshold Units area.
Display in Viewports (checkbox): Check this to display 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 checking this item. Note that double-clicking the object name in the list performs the same function as this checkbox.
The options in this area let you choose between two types of threshold units. Note that, switching between these two options does not alter the effect; it only 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 this 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.
Min Size/Max Size: These two spinners let you set 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 to fit your needs. Note that 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: As mentioned, 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.
If you need to access the Modify panel for one of the objects in the Level-of-Detail group, do this:
You can assign different materials to the various objects in the group. For example, you might want a very detailed map in the complex object, and a lightly detailed map in the less complex objects. It’s easiest to make these assignments before grouping the objects in the first place, but here’s how to assign materials to the objects within the group:
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.
If you look at a Level of Detail object in the Track View, you’ll only see the tracks for the subobject that’s currently displayed in the viewports. This is because, as a default, Show Only/Visible Objects is checked in the Track View Filters dialog. To see all subobjects in Track View, you need to uncheck Visible Objects.
If you need to dismantle a grouped Level-of-Detail object, and restore its subobjects to their independent states, do this:
The tracks for all of the subobjects in the Level-of-Detail object are now visible.
Note: It’s best to assign materials and mapping coordinates, as well as all modifiers while the objects are still separate. You can access them later, but it’s easier to do it at this point in the operation.
The name of the objects within the group appear in the Level of Detail list window, in order of complexity, only the least complex object in the group is displayed in the viewports, while all other objects are made invisible.