The progressive refinement

Let e be a given deviation error.

The pyramid will be traversed in the following way:

• At each level in the pyramid, e is compared to the average deviation of the node.
• If the traversal is terminated, otherwise the traversal proceeds downwards.

The result is an octree, which is a subset of the pyramide and whose leaves are the nodes of the pyramide with deviation error less than e.

Thus, we have higher resolution in "complicated" areas, than in more homogeneous ones.