Fedorkiw, J.Smith, C.Ghali, S.Louise M. Lever and Mary McDerby2014-01-312014-01-3120063-905673-59-2http://dx.doi.org/10.2312/LocalChapterEvents/TPCG/TPCG06/141-148Four methods for storing a set of points using a computer are currently known: Boundary representations, Constructive Solid Geometry, Binary Space Partitioning trees, and Nef polyhedra. We describe a time and spaceefficient BSP-based algorithm for computing the union of a set of solids and compare it with the other solid representations. The algorithm does not require that the entire tree fit in memory; it only needs to maintain the path from the root to one node in the tree at a time. We show that the algorithm is practical by providing time and space statistics. We also show the benefit of using the resulting union solid for computing interactive shadows.