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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 Copyright (c) 2010 kne / 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 math import sqrt
from Box2D import (b2FixtureDef, b2PolygonShape,
b2Transform, b2Mul,
b2_pi)
class ApplyForce (Framework):
name = "ApplyForce"
description = "Use w, a, and d to control the ship."
def __init__(self):
super(ApplyForce, self).__init__()
self.world.gravity = (0.0, 0.0)
# The boundaries
ground = self.world.CreateBody(position=(0, 20))
ground.CreateEdgeChain(
[(-20, -20),
(-20, 20),
(20, 20),
(20, -20),
(-20, -20)]
)
# TODO: make note of transform.R.set() -> transform.angle =
xf1 = b2Transform()
xf1.angle = 0.3524 * b2_pi
xf1.position = xf1.R * (1.0, 0.0)
xf2 = b2Transform()
xf2.angle = -0.3524 * b2_pi
xf2.position = xf2.R * (-1.0, 0.0)
self.body = self.world.CreateDynamicBody(
position=(0, 2),
angle=b2_pi,
angularDamping=5,
linearDamping=0.1,
shapes=[b2PolygonShape(vertices=[xf1 * (-1, 0), xf1 * (1, 0),
xf1 * (0, .5)]),
b2PolygonShape(vertices=[xf2 * (-1, 0), xf2 * (1, 0),
xf2 * (0, .5)])],
shapeFixture=b2FixtureDef(density=2.0),
)
gravity = 10.0
fixtures = b2FixtureDef(shape=b2PolygonShape(box=(0.5, 0.5)),
density=1, friction=0.3)
for i in range(10):
body = self.world.CreateDynamicBody(
position=(0, 5 + 1.54 * i), fixtures=fixtures)
# For a circle: I = 0.5 * m * r * r ==> r = sqrt(2 * I / m)
r = sqrt(2.0 * body.inertia / body.mass)
self.world.CreateFrictionJoint(
bodyA=ground,
bodyB=body,
localAnchorA=(0, 0),
localAnchorB=(0, 0),
collideConnected=True,
maxForce=body.mass * gravity,
maxTorque=body.mass * r * gravity
)
def Keyboard(self, key):
if not self.body:
return
if key == Keys.K_w:
f = self.body.GetWorldVector(localVector=(0.0, -200.0))
p = self.body.GetWorldPoint(localPoint=(0.0, 2.0))
self.body.ApplyForce(f, p, True)
elif key == Keys.K_a:
self.body.ApplyTorque(50.0, True)
elif key == Keys.K_d:
self.body.ApplyTorque(-50.0, True)
if __name__ == "__main__":
main(ApplyForce)
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