One of the greatest things about tessellation shaders is how easy it is to implement level-of-detail (LOD) algorithms. LOD is a general term in computer graphics that refers to the process of increasing/decreasing the complexity of an object's geometry with respect to the distance from the viewer (or other factors). As an object moves farther away from the camera, less geometric detail is needed to represent the shape because the overall size of the object becomes smaller. However, as the object moves closer to the camera, the object fills more and more of the screen, and more geometric detail is needed to maintain the desired appearance (smoothness or lack of other geometric artifacts).

The following image shows a few teapots rendered with tessellation levels that depend on distance from the camera. Each teapot is rendered using exactly the same code on the OpenGL side. The TCS automatically varies the tessellation levels based on depth:

When tessellation shaders are used, the tessellation level is what determines the geometric complexity of the object. As the tessellation levels can be set within the tessellation control shader, it is a simple matter to vary the tessellation levels with respect to the distance from the camera.

In this example, we'll vary the tessellation levels linearly (with respect to distance) between a minimum level and a maximum level. We'll compute the distance from the camera as the absolute value of the z coordinate in camera coordinates, (of course, this is not the true distance, but should work fine for the purposes of this example). The tessellation level will then be computed based on that value. We'll also define two additional values (as uniform variables): MinDepth and MaxDepth. Objects that are closer to the camera than MinDepth get the maximum tessellation level, and any objects that are further from the camera than MaxDepth will get the minimum tessellation level. The tessellation level for objects in between will be linearly interpolated.