** Intersection of Quadtrees**

Quadtrees *A* and *B* can be efficiently intersected:

- If
*A = 0*or*B = 0*, the result is*0*. - If
*A = 1*, the result is*B*. - If
*B = 1*, the result is*A*. - Otherwise, make a new interior node whose values are
corresponding intersections of children of
*A*and*B*.

Notice that the intersection can often reuse parts of the input trees. Uses include:

- Geospatial modeling, e.g. what is the intersection of area of forecast rain with area of corn?
- Graphics, games: view frustum culling
- Collision detection