Category: Personal

Hello again, today I bring you another lesson learnt.

When you choose Haxe for a project there are a wealth of 2D physics engines available, mostly ports of other popular engines, like Box2D. There are actually a few distinct ports to Haxe of various versions of B2D, but the most up-to-date and the one I’ve been using is Joshua Granick’s port of 2.1a. You can get it from Haxelib by opening a command prompt / terminal and running “haxelib install box2d”

In brief, it’s fantastic. Once you get a handle on how it works and where all the bits you want to use are it’s pretty simple, a far cry from the engine I initially experimented with – Physaxe – which was basically 20 pages of pure maths disguised as classes and functions! But there are some small issues I’ve run across while using it, and here comes the latest (and its solution, I wouldn’t leave you hanging!)

Continue reading “The intricacies of removing bodies in Box2D”

In my new tower defence project I need to know when certain things are touching, or when object A is within range of object B, and other nonsenses like that. It seems perverse now, but the first time I had to implement collision code a few years ago I didn’t know why the computer couldn’t TELL there was a collision: The blue circle is halfway-inside the red square, surely that’s obvious? But implement I did, and it was horrible and rough, but for that project it didn’t matter at all.

In the early days of this project I implemented a collision system again with just two shape types: Rectangle and circle. It worked well enough, but the performance was awful — I had time to knock together a few arrays and an update loop, but more advanced stuff like knowing which objects could be safely ignored to speed the whole process up takes time to write and test. Having experience with it previously, I ran back to Box2D, dropping the source in to my project so I could begin prodding.

Continue reading “Using Box2D as a collision system”