2D Game Dev – Part 12.2 – Distance Based Collision Detection |

This post is a portion of Part 12 in my on going series about 2D Game Development using the Allegro 5 library. These posts are in course order. You can see all of the posts in this course by clicking the “2D Game Development” button at the top of this site.

12.0 – Collision Detection
12.1 – Bounding Rectangle Collision Detection
12.2 – Distance Based Collision Detection
12.3 – Pixel Perfect Collision Detection

The next algorithm we are going to look at is called Distance based, or radius based collision detection. In this method, we determine the distance between the centers of two objects and then determine if it is less that the sum of their radii. Be sure to watch to see how, in my haze of being tired, I fail to notice that I am using the Pythagorean Theorem and instead identify the function used as the distance between two vectors.

Full source can be found here.

2 Comments

Glowworm on July 26, 2012 at 7:22 pm

Great Tutorials so far!
You probably know this, but I just wanted to point out that using sqrt() and pow() in your collision detection is ridiculously inefficient (unless your compiler is really good at optimizing and DWIM). A faster method would be:
if((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2)<(r1+r2)*(r1+r2)) { handle_collision(); }

Mike on July 31, 2012 at 11:21 pm

Cool, thanks for posting. I rarely work directly with math in my day to day and hadn’t really done any efficiency testing.
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2D Game Dev – Part 12.2 – Distance Based Collision Detection

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