AABBs

AABB stands for axis-aligned bounding box. It is a rectangular box whose edges are aligned with the coordinate axes, defined by minimum and maximum coordinates along each axis. In 3D, an AABB is described by min (xmin, ymin, zmin) and max (xmax, ymax, zmax); in 2D it is defined by (xmin, ymin) and (xmax, ymax). AABBs can also be represented by a center and extents (half-sizes).

AABBs are widely used in computer graphics, physics, and game development for fast, inexpensive broad-phase collision detection and frustum culling. They provide simple geometric tests that are cheaper than testing more complex shapes. Common operations include testing whether two AABBs intersect, whether a point lies inside an AABB, and computing unions of boxes.

Intersection tests between two AABBs rely on axis-wise overlap. In 3D, two boxes intersect if they overlap along all three axes: A.max.x >= B.min.x and A.min.x <= B.max.x, and similarly for y and z. If any axis separates the boxes, they do not intersect. For ray tracing or ray-scene queries, a slab method can be used to test intersection with an AABB by computing entry and exit parameters along each axis and combining them.

Construction often starts from a set of points or from an object's bounding geometry by taking coordinate-wise minima and maxima. AABB updating is cheap for translations but requires recomputation of corners (or center/extent) when the object rotates, since an axis-aligned box may no longer tightly bound the rotated object.

Limitations include loose fitting for rotated objects and potential overestimation compared with oriented bounding boxes. AABBs remain a fundamental tool for fast spatial queries and coarse collision handling.