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11.4. Use level of detail

LOD is a set of techniques that involve using different versions of an object with greater or less detail, depending on the distance from the camera.

When the object is close to the camera a full resolution, fully detailed object is displayed. When the object is further away a lower resolution, less detailed object is used. Figure 11.5 and Figure 11.6 show different levels of detail for asteroids.

Figure 11.5. Wireframe asteroids with levels of detail

Wireframe asteroids with levels of detail

Figure 11.6. Asteroids with levels of detail

Asteroids with levels of detail

The same technique applies to textures. High resolution textures are used for objects closer to the camera and lower resolution textures used for objects far away.

Applying LOD to objects reduces the usage of both compute power and memory bandwidth.

You can choose the LOD technique for different distances from the camera, Use the lowest level of detail that is appropriate but try lower levels to see if it makes much difference. Using fewer details requires less memory and bandwidth.

Another technique that you can use is to replace objects with billboards. As an object gets very small on screen small details become invisible. You can replace the object with a billboard with a texture that has an image of the object. This requires less computation to draw something that looks similar.

For example, consider a house with full details includes windows, window ledges and curtains all as 3D objects. As the camera moves away from the house the individual details can be simplified because the fine detail is no longer visible. At the furthest distances from the camera the house is so small on screen that you can draw it as a flat image of a house with no 3D details.

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