Taking the Development Ahead - Learn OpenGL ES: For Mobile Game and Graphics Development - page 229

long deltaTime,startTime,endTime;
startTime = SystemClock.uptimeMillis() % 1000;
gl.glClear(GLES20.GL_COLOR_BUFFER_BIT |
GLES20.GL_DEPTH_BUFFER_BIT);
updateModel(Counter.getUpDownValue(), _zAngle);
renderModel(gl);
endTime = SystemClock.uptimeMillis() % 1000;
deltaTime = Math.abs(endTime - startTime);
if (deltaTime < 20) {
try {
Thread.sleep(20 - deltaTime);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
In Listing 6-8 , the local variable deltaTime stores the time taken by the current
frame, which is nothing but the time taken by the method calls updateModel()
and renderModel() . If deltaTime is less than 20 milliseconds, the Renderer
thread is blocked for (20 - deltaTime) milliseconds. If it is more than that, the
thread is not blocked.
Including Missiles for the Tank
For the Tank Fence game, point sprites will be used as missiles. Although we can use
other primitives to represent missiles, using point sprites for this purpose will make
things a lot easier.
Create a new Java class called Missile , inside the src folder for the TANK FENCE
GAME 2 application. Because we are using point sprites to represent missiles, the
Missile object ( Listing 6-9 ) must contain fields to store the x, y, and z coordinates
of the source and destination position of point sprite. For this, create the correspond-
ing fields as shown in Listing 6-9 .