Modern games include fixtures that do not react physically to collisions with other fixtures but still have an important mission, just like radars that detect intruders within an area.

Usually, allies do not crash between themselves and others like ghosts will collide only with fire.

All such gameplay variables are easily implemented with Box2D, so you will not have to fill your collision handlers with many lines of code. In addition, filtering collisions will allow you to decrease the CPU load.

In this recipe, you will learn how to use sensors and manage the different ways of filtering your collisions depending on the complexity of the game.