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.
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.
Check out this tutorial by Gavin Goulden
01 Prepare your models
To begin, make sure that you are absolutely happy with your base mesh. Though this can be altered and changes can be propagated in the future, it is always a good idea to have a solid starting point you are confi dent with. This model will not only be the base for future head sculpts, but will serve as the highest resolution game model for your character’s head. Things to double-check are proper edge flow around deforming areas, that the character is properly unwrapped for texture painting, that all of the vertices are welded as expected and so on.
02 Drop detail
Once you are happy with your base mesh, LOD1, duplicate the model and name it LOD2. This model will be a reduced version of your original and, in-game, should come into view when the character is a certain distance away from the camera. Of course, this setting is adjusted in every game so there is no hard and fast rule, but a safe guess is to reduce each model’s triangle count by half. So, if our original model was 8,000 triangles, the next should be 4,000 and the next at 2,000 or lower.
03 Minimum detail
Next, duplicate the LOD2 model and rename the new copy LOD3. This model will be last in the set and can be a very loose version of the original. Generally speaking, this model would have no facial bones altering the mesh and is intended to be a representation of the final product at a very far distance.
04 Skin Wrap modifier
Once all of your LOD models have been created, you can unhide all of them, select LOD2 and add a Skin Wrap modifier from the modifier list. Once the modifier is applied, open it up and add LOD1 as the target. Repeat the process for LOD3. The idea here is that when LOD1 becomes altered, the changes will be carried over to the LOD2 and LOD3 meshes or at least as close as their reduced meshes will allow.
05 New faces
Next, you can feel free to duplicate your original head and alter the mesh to create new faces. This can be done in Max or by re-exporting your lowest subdivision in ZBrush. The only important thing to keep in mind is that the vertex count cannot be altered. This means that no additional geometry can be added, nor can any be taken away.
06 Morph
The reason why no vertex information can be added or subtracted is that you will now be using morph targets to automatically create your LOD models for each head. Grab your LOD1 model and apply a Morpher modifier from the modifier list. Click on the Load Multiple Targets option and select the new face that you created. Increase the value to 100, which means that the final shape will be the new face 1:1. As long as the Skin Wrap modifier is enabled on your reduced meshes, they should also deform along with the Morpher effect on the original mesh.
Possible issues
A flaw in this workflow is that if the vertex index on the original mesh (or rather, new meshes that will be created from it) becomes altered, the Morpher modifi er will not work. Of course, no matter how careful you are, if you are detailing with a high volume of character assets, something is bound to come up. Either a rogue vertex gets added, a face gets deleted or vertices become welded upon import and export from diff erent programs – you get the idea. However, there are many ways to fi x this problem, such as vertex reordering scripts that can be installed in Max. I suggest using the Morphix plug-in which is a free tool that grabs a master and slave mesh, copying one vertex order to the other.
