Game Physics Engine Development, 2nd Edition

288 Chapter 12 Collision Detection

object and objects in the same or neighboring cells (there are a maximum of three

neighbors to check now because objects can’t be in a grid cell that is smaller than they

are). In addition, the object is check ed against all objects in all cells in larger-celled

grids that overlap.

We don’t need to check against objects in smaller-celled grids, because the small

objects are responsible for checking against larger objects.

For each grid in the map, we can use the grid data structure with the same set

of occupied cells. However, we need to add a cell to the active list if it contains any

objects at all (they may be in contact with neighbo rs).

12.5 Summary

Collision detection is a complex and time-consuming process.