/**
* A generalized Pong AI player. Takes a Rect object and a Ball, computes where the ball will be
* when ball.y == rect.y, and tries to move toward that x-coordinate. If the ball is moving
* straight it will try to clip the ball with the edge of the paddle.
*
* @param cpu
*/
private void aiPrediction(Paddle cpu, Paddle opponent) {
Ball ball = new Ball(mBall);
// Special case: move torward the center if the ball is blinking
if (mBall.serving()) {
cpu.destination = getWidth() / 2;
cpu.move(true);
return;
}
// Something is wrong if vy = 0.. let's wait until things fix themselves
if (ball.vy == 0) return;
// Y-Distance from ball to Rect 'cpu'
float cpuDist = Math.abs(ball.y - cpu.centerY());
// Y-Distance to opponent.
float oppDist = Math.abs(ball.y - opponent.centerY());
// Distance between two paddles.
float paddleDistance = Math.abs(cpu.centerY() - opponent.centerY());
// Is the ball coming at us?
boolean coming =
(cpu.centerY() < ball.y && ball.vy < 0) || (cpu.centerY() > ball.y && ball.vy > 0);
// Total amount of x-distance the ball covers
float total =
((((coming) ? cpuDist : oppDist + paddleDistance)) / Math.abs(ball.vy)) * Math.abs(ball.vx);
// Playable width of the stage
float playWidth = getWidth() - 2 * Ball.RADIUS;
float wallDist = (ball.goingLeft()) ? ball.x - Ball.RADIUS : playWidth - ball.x + Ball.RADIUS;
// Effective x-translation left over after first bounce
float remains = (total - wallDist) % playWidth;
// Bounces the ball will incur
int bounces = (int) ((total) / playWidth);
boolean left = (bounces % 2 == 0) ? !ball.goingLeft() : ball.goingLeft();
cpu.destination = getWidth() / 2;
// Now we need to compute the final x. That's all that matters.
if (bounces == 0) {
cpu.destination = (int) (ball.x + total * Math.signum(ball.vx));
} else if (left) {
cpu.destination = (int) (Ball.RADIUS + remains);
} else { // The ball is going right...
cpu.destination = (int) ((Ball.RADIUS + playWidth) - remains);
}
// Try to give it a little kick if vx = 0
int salt = (int) (System.currentTimeMillis() / 10000);
Random r = new Random((long) (cpu.centerY() + ball.vx + ball.vy + salt));
int width = cpu.getWidth();
cpu.destination =
(int)
bound(
cpu.destination + r.nextInt(2 * width - (width / 5)) - width + (width / 10),
0,
getWidth());
cpu.move(true);
}
