What is AABB - Collision detection?

collision-detection aabb
SemperAmbroscus picture SemperAmbroscus · Mar 19, 2014 · Viewed 46.7k times · Source

Hi I'm making a voxel game in Java and while researching all the different things I'd need to learn, I noticed that a lot of games use AABB for collision detection. And then I remembered seeing AABB in Minecraft also. But when I google what AABB is, it only comes up with other peoples code, or some organization out the history book. Stackoverflow, what is AABB?

Answer

jwd picture jwd · Mar 19, 2014

AABB stands for "Axis-Aligned Bounding Box."

It is a fairly computationally- and memory-efficient way of representing a volume, typically used to see if two objects might be touching.

Since it is axis-aligned, it does not necessarily "fit" your real 3D object very well. AABB checks are often used as a coarse first-approximation to see if objects might be colliding. Then, if the AABB check passes, more detailed checks are made.

Example:

Imagine your world is 2D, and you draw it on a sheet of graph paper. You have some objects in the world (a ball, a tree, whatever). To make an AABB for one of the objects, you draw a rectangle around the object, making your lines parallel to the grid lines on the paper.

If you have the AABB for two objects, you can do some pretty simple math to see if those AABBs overlap. If they don't overlap, those two objects couldn't possibly be touching, so it's an easy early-out for your collision algorithm.

This generalizes to 3D (and more-Ds) fairly easily.

You might want to check out gamedev.stackexchange.com, too.

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