1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
|
#!/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)
|
