Selective refinement. The selective refinement is the way for increase or decrease detail, only where as needed. This technology increase the render speed, decreasing the number of triangles to render, and decreasing the band-width needed between the central processor and the graphic processor.    The decision about the increase or decrease detail depend of a selective critera: light, visibility or other conditions. In the case of figure, the selective criteria is visibility.

Selective loading. Another aplication of selective refinement as loader only the data with as needed. This technology is the way for render very big images, because it don't depend of system memory.