Radar

The radar is one of the most vital components of your robot. Without it targeting is effectively impossible, and movement is purely random. Just as with movement and targeting, there are many simple and complex algorithms for radar control. In most robots the radar takes up the smallest portion of code.

Most robocoders place thier radar adjustment code at the end of the onScannedRobot method, this by istelf is not a mistake and generally has little effect. However in robots that do alot of processing, it is best to place it at the beginning of the onScannedRobot method or in the main loop, as to allow the radar to reset if the robot skips its turn in a later method.

Example code

NOTE: for most of these radar locks, you will need to add one of the following to your run() method:

setAdjustRadarForRobotTurn(true);

setAdjustGunForRobotTurn(true);
setAdjustRadarForGunTurn(true);

Spinning radar

To just spin the radar, add this to your run() method:

setTurnRadarRightRadians(Double.POSITIVE_INFINITY);

The infinity lock

The infinity lock is the simplest radar lock, and is used frequently in Nano bots. It has the disadvantage of "slipping" and losing its lock frequently.

public void run() {
    // ...
    setTurnRadarRightRadians(Double.POSITIVE_INFINITY);
}

public void onScannedRobot(ScannedRobotEvent e) {
    // ...
    setTurnRadarLeftRadians(getRadarTurnRemainingRadians());
}

Perfect radar locks

There are several "perfect" radar locks that will not slip once they have a lock. Here is one:

Thin lock

This type of lock is thin and follows the robots around the stage.

import robocode.util.Utils;

public void run() {
    // ...
    turnRadarRight(Double.POSITIVE_INFINITY);
    do {
        scan();
    } while (true);
}

public void onScannedRobot(ScannedRobotEvent e) {
    // ...
    double absoluteBearing = getHeadingRadians() + e.getBearingRadians();
    double radarTurn = absoluteBearing - getRadarHeadingRadians();
    setTurnRadarRightRadians(Utils.normalRelativeAngle(radarTurn));
}

Wide lock

Another type of "perfect" radar, that is think and practices by who have space to spare and want to avoid the rare slipping of the thin lock.

import robocode.util.Utils;

int ticksSinceLastScan = 0;
public void run() {
    // ...
    do {
        if (ticksSinceLastScan++ > 2)
            setTurnRadarRight(Double.POSITIVE_INFINITY);

        execute();
    } while (true);
}

public void onScannedRobot(ScannedRobotEvent e) {
    double absoluteBearing = getHeadingRadians() + e.getBearingRadians();
    double radarTurn = Utils.normalRelativeAngle(absoluteBearing - getRadarHeadingRadians());

    // Width of the bot, plus twice the arc it can move in a tick
    double arcToScan = atan(36.0 / e.getDistance());

    //Limit this so that we don't overshoot
    if (arcToScan > PI / 4.0) arcToScan = PI / 4.0;

    //We want to sent the radar even further in the direction its moving
    radarTurn += (radarTurn < 0) ? -arcToScan : arcToScan;
    setTurnRadarRightRadians(radar);

    ticksSinceLastScan = 0;

    // ...
}