BIH

BIH (Bounding Interval Hierarchy) is a partitioning data structure similar to BSP (Binary Space Partitioning).

Some general attributes:
 * Very fast construction times
 * Low memory footprint
 * Simple and fast traversal
 * Very simple construction and traversal algorithms
 * High numerical precision during construction and traversal
 * Flatter tree structure (decreased tree depth) compared to kd-trees

In Darkplaces, BIH is overlay implementation. Being activated, it replaces default BSP implementation in collision code. BIH is faster than BSP, requires less memory, and much more stable at arbitrary triangle meshes.