Friday, July 5, 2013

Developing 3d game for Android

To develop real 3D game is not trivial task no matter what platform you target.

Five or six  years ago I was experimenting with JOGL - Java Binding for the OpenGL API trying to develop 3D game in java for PC.
In that time it was common opinion that 3D games can only be devleoped with C++ since java is too slow. Even then that was not true. JOGL delegates all rendering to OpenGL , and in initialization phase you can create complex objects in OpenGL memory so later you can reference it from java and give short instructions to OpenGL in order to move or rotate that object. That means that java only have to manage positions and rotations of the objects, check collisions and of course game logic.

Since rendering is most demanding part of 3D game and it is handled by OpenGL ,  C++ being faster then java doesn't matter so much. Of course , in Java you will probably have to optimize more, but it is definitely fast enough.

I was very happy how my experiment turned out. Although I never finished and published the game, I managed to make nice little space combat with real LAN multiplayer so players could fight in space. It had laser guns, missiles that follow the targets, radar, etc. It was running smooth both on Windows and Linux.

Today, even cheap smartphones (like my HTC Explorer) have similar CPU power and memory my PC had at time I was playing with JOGL.

Smartphones support OpenGLES - The Standard for Embedded Accelerated 3D Graphics. Most phones support OpenGL ES 2.0, only older models still use OpenGL ES 1.x.

Working with JOGL, developer actually has to know much about OpenGL since JOGL is not a 3D engine, it is just a bridge between Java and OpenGL which allows us to call OpenGL commands from Java code.

In recent years several good 3D libraries emegred, making 3D apps development much easier. Since they manage low level OpenGL calls, you can focus more on your game logic.

There is a great OpenGL ES 2.0 based 3D engine for Android platform called Rajawali, developed by Dennis Ippel (great job Dennis). There is also Android Demo app that demonstrate Rajawali engine features.

Basic feature that every 3D engine provides is loading external 3D model, adding it to 3D scene and manipulating it's position and rotation. Most 3D engines provide much more features including collision checking, physics, lighting, various visual effects, etc.

Rajawali's set of features amazed me so I decided to try it out by  making simple 3D game that focuses on playability  rather then on visual attraction. As a kid a loved games like Galaga and Phoenix because they were dynamic and addictive. My goal is to achieve similar gameplay dynamic in 3D world.  Although I limited ships freedom to move to a plane (can't go up or down), 3D perspective gives me more "space" (player can see distant enemy ships much earlier that it would be possible if the view was from above) and of course 3D models of ships and meteors look more realistic then it can be achieved in 2D.

Here are first screenshots of the game :

So far everything works fine on HTC Explorer (Android 2.3.5) and HTC Desire C (Android 4.0). 
I'll keep you posted about my progress here.

No comments: