Rajawali Tutorial 4: Optimisation

The onSurfaceCreated() method in the Renderer is called every time the rendering starts or whenever the context is lost. This typically happens when the orientation changes or when the device wakes up after going to sleep.

When the context is lost, all the textures are deleted from memory. This is not something Rajawali inflicts upon you. This is the way OpenGL ES on Android works. So you always have to re-create your textures in the onSurfaceCreated() method.

Object instantiation however is something that needs to be done only once. So in onSurfaceCreated you could use the following code (make sure you set mClearChildren to false):

@Override
public void onSurfaceCreated(GL10 gl, EGLConfig config) {
	mClearChildren = false;

	if(sceneInitialized == false) {
		mLight= new DirectionalLight();
		mLight.setPosition(3, 5, -3);

		mSphere =  = new Sphere(1, 24, 24);
		mSphere.addLight(mLight);
		addChild(mSphere);
	}
	SimpleMaterial simple = new SimpleMaterial();
	mSphere.setMaterial(simple);
	Bitmap texture = BitmapFactory.decodeResource(mContext.getResources(), R.drawable.mytexture);
	mSphere.addTexture(mTextureManager.addTexture(texture));
}

This speeds things up significantly when the context has to be re-created, especially when you use large models.

There’s another optimisation you can use when large models are involved. It’s called serialization. This prevents you from having to load a .obj file and parse it every time the application starts up. It basically writes all the relevant data (vertices, indices, normal, texture coordinates and colors) to a binary file on disk.

So the .obj file has to be loaded only once during development. Once the file has loaded you can save it to the sdcard.
In order to do this you first have to set the permission in AndroidManifest.xml:

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

Then the .obj model can be loaded in and turned into a serialized file:

	mSphere.serializeToSDCard("my_serialized_model.ser");

When this is done the code and the .obj file can be discarded. The serialized file is written to the sd card and should be copied into to your resources folder (res/raw). The serialized model is now ready to be loaded into your application:

try {
	ObjectInputStream ois;
	ois = new ObjectInputStream(mContext.getResources().openRawResource(R.raw.my_serialized_model));
	mMyModel = new BaseObject3D((SerializedObject3D)ois.readObject());
	addChild(mMyModel);
	ois.close();
} catch (Exception e) {
	e.printStackTrace();
}

WIN!

Continue to Rajawali Tutorial 5: Skybox.