run_simulation.py

import Box2D  # The main library
# Box2D.b2 maps Box2D.b2Vec2 to vec2 (and so on)
from Box2D.b2 import (world, polygonShape, circleShape, staticBody, dynamicBody)
import state_history as sh


#TODO: tweak those, maybe pass them to setup
min_move = 0.5 #min move before we say, we're stuck [m]
max_stuck_time = 2 #max time being stuck before we finish [s]

#TODO: tweak setup, fix bugs, get a cleaning up function...

class Simulation:
    def __init__(self, track, vehicle, save=False):
        self.track = track
        self.vehicle = vehicle

        # Create the world
        self.sim_world = world(gravity=(0, -10), doSleep=True)
        # Create the track (static ground body)
        self.track.build(self.sim_world)

        x0, y0 = self.track.get_spawn_pos()
        self.vehicle.build(self.sim_world, x0, y0)

        self.tracker = self.vehicle.tracker
        self.starting_position = self.tracker[0] #just x coordinate

        # Only init history after track was built
        self.history = sh.StateHistory(self.track) if save else None

    #returns dist covered and whether it is over (bool)
    def run(self, n_iter=-1, speed=1.):
        stuck_time = 0

        #FIXME: unfortunately speed affects physics...
        time_step = speed/60. #60 Hz by default
        vel_iters, pos_iters = 6, 2 #apparently good
        i = 0
        while True:
            self.sim_world.Step(time_step, vel_iters, pos_iters)
            if self.history: self.history.save_state(self.vehicle)

            #check if we're moving forward
            position = self.tracker[0]
            distance = position - self.starting_position
            if distance < min_move:
                stuck_time += time_step
            else:
                stuck_time = 0

            # if we're stuck for too long finish the loop
            if stuck_time > max_stuck_time:
                print "Stuck in one place"
                return distance, True, n_iter

            i+= 1
            if n_iter>0 and i > n_iter:
                print "Reached max time", n_iter*time_step, "s"
                return distance, False, n_iter

            if self.tracker[1] < 0:

                print "Fell off the cliff"
                return distance, True, n_iter

        #return final distance
        print "Normal"
        return (distance, False, n_iter)