2D Game Programming Tricks - Beginning Android Games - page 418

The TextureRegion s get initialized in the resume() method, as they depend on the Texture :
@Override
public void resume() {
texture = new Texture(((GLGame)game), "atlas.png");
cannonRegion = new TextureRegion(texture, 0, 0, 64, 32);
ballRegion = new TextureRegion(texture, 0, 32, 16, 16);
bobRegion = new TextureRegion(texture, 32, 32, 32, 32);
}
No surprises here. The last thing we need to change is the present() method. You'll be surprised
how clean it's looking now. Here it is:
@Override
public void present( float deltaTime) {
GL10 gl = glGraphics.getGL();
gl.glClear(GL10.GL_COLOR_BUFFER_BIT);
camera.setViewportAndMatrices();
gl.glEnable(GL10.GL_BLEND);
gl.glBlendFunc(GL10.GL_SRC_ALPHA, GL10.GL_ONE_MINUS_SRC_ALPHA);
gl.glEnable(GL10.GL_TEXTURE_2D);
batcher.beginBatch(texture);
int len = targets.size();
for ( int i = 0; i < len; i++) {
GameObject target = targets.get(i);
batcher.drawSprite(target.position.x, target.position.y, 0.5f, 0.5f, bobRegion);
}
batcher.drawSprite(ball.position.x, ball.position.y, 0.2f, 0.2f, ballRegion);
batcher.drawSprite(cannon.position.x, cannon.position.y, 1, 0.5f, cannon.angle,
cannonRegion);
batcher.endBatch();
}
That is super sweet. The only OpenGL ES calls we issue now are for clearing the screen,
enabling blending and texturing, and setting the blend function. The rest is pure SpriteBatcher
and Camera2D goodness. Since all our objects share the same texture atlas, we can render them
in a single batch. We call batcher.beginBatch() with the atlas texture, render all the Bob targets
using the simple drawing method, render the ball (again with the simple drawing method), and
finally render the cannon using the drawing method that can rotate a sprite. We end the method
by calling batcher.endBatch() , which will actually transfer the geometry of your sprites to the
GPU and render everything.
Measuring Performance
So how much faster is the SpriteBatcher method than the method you used in BobTest ? Let's
take the BobTest code and rewrite it using your new OpenGL ES classes. We add an FPSCounter
to the code, increase the number of targets to 100 and set the maximum number of sprites the