Binary Space Partition
A binary space-partitioning (BSP) tree is an efficient method for determining object visibility by painting surfaces onto the screen from back to front, as in the painter's algorithm. The BSP tree is particularly useful when the view reference point changes, but the objects in a scene are at fixed positions.
Applying a BSP tree to visibility testing involves identifying surfaces that are "inside" and "outside" the partitioning plane at each step of the space subdivision, relative to the viewing direction. The basic concept in this algorithm. With plane P1, we first partition the space into two sets of objects. One set of objects is behind, or in back of, plane P1 relative to the view plane P1, we divide that object into two separate objects, labeled A and B. Objects A and C are in front of P1, and objects B and D are behind P1. We next partition the space again with plane P2 and construct the binary tree. In this tree, the objects are represented as terminal nodes, with front objects as left branches and back objects as right branches.