Blog about (Web-) Programming, Graphics and Games.


Java Physics Demo: Boxes

This demo uses parts of the the JBullet and the Vecmath library. I extracted essential classes and put them all into 1 java source file. Thus this demo dont needs external libraries.

On Objectstacks
I also changed the used JBullet parts, so that they dont use Objectstacks. Objectstacks were introduced to manage temporary objects in a threadsafe way. There are 3 possibilities to deal with temporary objects:
  • 1) Just instantiate a temporary object as you need it. Problem: this can result in a lot instantiated objects, garbage collector has alot todo, runtime performance might drop. Though, intelligent jit-compilers could possibly handle multiply temporary instantiations and could in a way inline them..
  • 2) Add (private) auxiliary objectvariables to the class. You can use this objects in computation and dont need to instantiate new ones. Problem: if different threads invoke the same method at the same time, an object could be used twice, with unexpected results. This approach is not thread-safe.
  • 3) Use objectstacks. Retrieve auxiliary objects from a pool and return them to the pool, when computation is over. This way in most cases only limited number of instantitions is needed (opposed to possibly unlimited instantiations in approach 1) and this method is threadsafe (opposed to approach 2).
The original JBullet library uses objectstacks. In this demo I omitted them, because the original approach requires an instrumentation step in the build process. During this step auxiliary classes are generated using an ant-build-file. A simple compile doesnt work. For sake of simplicity I thus dont use objectstacks here, but above second technique. Thus this demo is not thread-safe, but its usecase is only single threaded, so it doesnt matter.

How to build
  • Make sure, that a JDK is installed.
  • Put the source file into a directory 'net/plsw/bullet'.
  • Compile it with 'javac net/plsw/bullet/'.
  • Run it with 'java net.plsw.bullet.BoxDemo'.


Canvas Game Demo: 4Rumble

As a small project besides a more complex 3d-project (soon more infos here) i wrote this game demo for canvas and javascript. Its a remake of a flash game demo, named 4Rumble (click, click), i made a while back. In this Javascript demo there is currently only one character, Cursor-Left/Right make him run around. Cursor-Up/Down zooms in and out. A formerly flash demo ported to javascript, might be seen as statement in the current html5-instead-of-flash debate. Which leads to:

Others stuff ramblings
My opinion about the Apple/Html5 vs. Flash debate (click, click): I dont have much to do with apple and i dont have much todo with flash. So im not directly affected. Obviously, Html5 is more open and accessible, than flash, so I love to see it gain ground. On the other side I strongly dislike vendor-lockin on Iphone (and elsewhere, e.g. linux-ban on ps3). It kills creativity, the user should have the choice between different technologies. If native apps are better than those (compiled) with intermediate code, they will supersede naturally other apps. There is no need for prohibition. If apple would allow flash (or more importantly imo: java) on its devices, I maybe also wanted to have one. :)
And now for sth. completely different: Google makes O3d a WebGl-Javascript-library, the plugin-development is stopped. This is imo a good step since with WebGl there wont be a need for a browser-3D-plugin. Though, WebGl doesnt currently run everywhere (i.e. on i.e.), but according to google the plugin will still be available for at least a year.