How do I find enemies with the scanner?

Search, then lock on

from bot import Chassis, Scanner, wait

chassis = Chassis(0)
scanner = Scanner(1)

sweep = 0
while True:
    if scanner.ping(0):
        b = scanner.bearing(0)
        scanner.sense = b      # keep the arc on it
        log("contact @ {}", b)
    else:
        sweep += 30            # nothing: look at the next 30 degrees
        if sweep >= 180:
            sweep -= 360
        scanner.sense = sweep
    wait()

Moving the arc 30° a tick covers the whole circle in 12 ticks, a little over half a second.

What the scanner tells you

• scanner.sense = deg points the arc (15° either side) at a field bearing. It stays on that bearing as the chassis turns. It starts at 0, facing east. The new arc's readings come in after the next wait().
• scanner.ping(i) is true if slot i (0 to 3) holds a contact. Contacts are sorted by bearing from right to left, so slot 0 is the rightmost.
• scanner.bearing(i) is that contact's field bearing. Check ping(i) first: an empty slot's bearing means nothing.
• scanner.any is true if anything pinged in the arc this tick.

Friend, foe or wall?

A contact is anything solid in line of sight within 30 m: an enemy, a teammate, a block or a wall. Some ways to tell them apart:

• Watch what moves. Obstacles stay put; bots move. The house bot seeker looks twice from different places to fix where a contact is.
• Know where your teammate is. A radio gives your teammate's position (radio.teammate()), so you can skip a contact in line with it.
• Measure the distance. A rangefinder pointed at the same bearing (rangefinder.bearing = b) gives rangefinder.range in metres, so you can tell a near bot from a far wall.
• Look at its shape. scanner.profile(i) asks for a contact's silhouettes, front and side. The answer comes in after the next wait(): scanner.profiled is true if it found a bot (a wall gives no profile), and scanner.front_width, scanner.front_height and the rest describe its shape. A profile doesn't say which team the bot is on.

Tips

• After you point a sensor somewhere new, its reading comes a tick later. Trust what it says once it has been on a target for more than a tick.
• Sweep while you drive, but point the arc ahead of you now and then (scanner.sense = chassis.heading) so you see what you're driving into.
• The scanner also warns of a heat-seeking missile coming at you: scanner.missile and scanner.missile_bearing.