Game Physics Cookbook

Circle to circle

Determining if two circles intersect is extremely simple. If the length of a line going from the center of circle A to the center of circle B is less than the sum of the two circles, radii, they intersect. Of course, we want to avoid the expensive square root operation performed when finding the length of a line. To avoid this, we can compare the square length of the line against the square sum of the two circles, radii:

Getting ready

We are going to implement a function to detect the collision between two circles. To avoid the expensive square root operation involved in finding the distance between two circles, we're going to find ...