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#!/usr/bin/env python
# -*- coding: utf-8 -*-
#
# C++ version Copyright (c) 2006-2007 Erin Catto http://www.box2d.org
# Python version by Ken Lauer / sirkne at gmail dot com
#
# This software is provided 'as-is', without any express or implied
# warranty. In no event will the authors be held liable for any damages
# arising from the use of this software.
# Permission is granted to anyone to use this software for any purpose,
# including commercial applications, and to alter it and redistribute it
# freely, subject to the following restrictions:
# 1. The origin of this software must not be misrepresented; you must not
# claim that you wrote the original software. If you use this software
# in a product, an acknowledgment in the product documentation would be
# appreciated but is not required.
# 2. Altered source versions must be plainly marked as such, and must not be
# misrepresented as being the original software.
# 3. This notice may not be removed or altered from any source distribution.
from .framework import (Framework, Keys, main)
from .bridge import create_bridge
from math import sqrt
from Box2D import (b2CircleShape, b2EdgeShape, b2FixtureDef, b2PolygonShape,
b2_pi)
def create_car(world, offset, wheel_radius, wheel_separation, density=1.0,
wheel_friction=0.9, scale=(1.0, 1.0), chassis_vertices=None,
wheel_axis=(0.0, 1.0), wheel_torques=[20.0, 10.0],
wheel_drives=[True, False], hz=4.0, zeta=0.7, **kwargs):
"""
"""
x_offset, y_offset = offset
scale_x, scale_y = scale
if chassis_vertices is None:
chassis_vertices = [
(-1.5, -0.5),
(1.5, -0.5),
(1.5, 0.0),
(0.0, 0.9),
(-1.15, 0.9),
(-1.5, 0.2),
]
chassis_vertices = [(scale_x * x, scale_y * y)
for x, y in chassis_vertices]
radius_scale = sqrt(scale_x ** 2 + scale_y ** 2)
wheel_radius *= radius_scale
chassis = world.CreateDynamicBody(
position=(x_offset, y_offset),
fixtures=b2FixtureDef(
shape=b2PolygonShape(vertices=chassis_vertices),
density=density,
)
)
wheels, springs = [], []
wheel_xs = [-wheel_separation * scale_x /
2.0, wheel_separation * scale_x / 2.0]
for x, torque, drive in zip(wheel_xs, wheel_torques, wheel_drives):
wheel = world.CreateDynamicBody(
position=(x_offset + x, y_offset - wheel_radius),
fixtures=b2FixtureDef(
shape=b2CircleShape(radius=wheel_radius),
density=density,
)
)
spring = world.CreateWheelJoint(
bodyA=chassis,
bodyB=wheel,
anchor=wheel.position,
axis=wheel_axis,
motorSpeed=0.0,
maxMotorTorque=torque,
enableMotor=drive,
frequencyHz=hz,
dampingRatio=zeta
)
wheels.append(wheel)
springs.append(spring)
return chassis, wheels, springs
class Car (Framework):
name = "Car"
description = "Keys: left = a, brake = s, right = d, hz down = q, hz up = e"
hz = 4
zeta = 0.7
speed = 50
bridgePlanks = 20
def __init__(self):
super(Car, self).__init__()
# The ground -- create some terrain
ground = self.world.CreateStaticBody(
shapes=b2EdgeShape(vertices=[(-20, 0), (20, 0)])
)
x, y1, dx = 20, 0, 5
vertices = [0.25, 1, 4, 0, 0, -1, -2, -2, -1.25, 0]
for y2 in vertices * 2: # iterate through vertices twice
ground.CreateEdgeFixture(
vertices=[(x, y1), (x + dx, y2)],
density=0,
friction=0.6,
)
y1 = y2
x += dx
x_offsets = [0, 80, 40, 20, 40]
x_lengths = [40, 40, 10, 40, 0]
y2s = [0, 0, 5, 0, 20]
for x_offset, x_length, y2 in zip(x_offsets, x_lengths, y2s):
x += x_offset
ground.CreateEdgeFixture(
vertices=[(x, 0), (x + x_length, y2)],
density=0,
friction=0.6,
)
# Teeter
body = self.world.CreateDynamicBody(
position=(140, 0.90),
fixtures=b2FixtureDef(
shape=b2PolygonShape(box=(10, 0.25)),
density=1.0,
)
)
self.world.CreateRevoluteJoint(
bodyA=ground,
bodyB=body,
anchor=body.position,
lowerAngle=-8.0 * b2_pi / 180.0,
upperAngle=8.0 * b2_pi / 180.0,
enableLimit=True,
)
# Bridge
create_bridge(self.world, ground, (2.0, 0.25),
(161.0, -0.125), self.bridgePlanks)
# Boxes
for y_pos in [0.5, 1.5, 2.5, 3.5, 4.5]:
self.world.CreateDynamicBody(
position=(230, y_pos),
fixtures=b2FixtureDef(
shape=b2PolygonShape(box=(0.5, 0.5)),
density=0.5,
)
)
car, wheels, springs = create_car(self.world, offset=(
0.0, 1.0), wheel_radius=0.4, wheel_separation=2.0, scale=(1, 1))
self.car = car
self.wheels = wheels
self.springs = springs
def Keyboard(self, key):
if key == Keys.K_a:
self.springs[0].motorSpeed = self.speed
elif key == Keys.K_s:
self.springs[0].motorSpeed = 0
elif key == Keys.K_d:
self.springs[0].motorSpeed = -self.speed
elif key in (Keys.K_q, Keys.K_e):
if key == Keys.K_q:
self.hz = max(0, self.hz - 1.0)
else:
self.hz += 1.0
for spring in self.springs:
spring.springFrequencyHz = self.hz
def Step(self, settings):
super(Car, self).Step(settings)
self.viewCenter = (self.car.position.x, 20)
self.Print("frequency = %g hz, damping ratio = %g" %
(self.hz, self.zeta))
if __name__ == "__main__":
main(Car)
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