ABSTRACT
This chapter aims to understand how regular-grid acceleration schemes work, discusses the speed-up factors they can achieve, shows how to place transformed objects in grids and describes have implemented a regular grid. Common techniques use bounding volume hierarchies, octrees, binary space partition trees, kd-trees, and regular grids. The hit function must be able to handle rays that start inside or outside the grid. The boxes are arranged so that the grid’s bounding box is a cube centered on the origin with one box at each corner. Each box therefore has three faces in the bounding-box faces. A random cube of spheres is ideal for the grid structure, particularly when there are large numbers of spheres uniformly distributed in the cube. Bounding volume hierarchies are more adaptive to the scene geometry than grids because the cell sizes and locations are determined by the objects.
