from abc import ABCMeta, abstractmethod, abstractproperty
from ... import exceptions as exc
from ...lib.pydispatch import dispatcher
from ...utils import mathematical as mut
from . import signals
#==============================================================================
# Environment
#==============================================================================
[docs]class Engine(object):
__metaclass__ = ABCMeta
world_class = None
[docs]class World(object):
__metaclass__ = ABCMeta
@abstractmethod
def __init__(self, gravity, *args, **kwargs):
self._inner_object = None
@property
def inner_object(self):
return self._inner_object
@abstractproperty
def gravity(self):
pass
@abstractmethod
[docs] def step(self, time_step):
"""Subclasses implementing this method must send the corresponding
signals, defined in :mod:`ars.model.physics.signals`.
"""
pass
#==============================================================================
# Parents
#==============================================================================
[docs]class Body(object):
__metaclass__ = ABCMeta
@abstractmethod
def __init__(self, mass=None, density=None, pos=None, rot=None,
*args, **kwargs):
if mass is not None:
if density is not None:
raise exc.ArsError('Both mass and density arguments were given')
self._inner_object = None
self._attached_geom = None
self._saved_linear_vel = None
self._saved_angular_vel = None
[docs] def attach_geom(self, geom):
geom.attach_body(self)
self._attached_geom = geom
dispatcher.send(signals.BODY_POST_ATTACH_GEOM, sender=self)
#==========================================================================
# Calculations
#==========================================================================
[docs] def calc_translation_kinetic_energy(self):
r"""Calculate the kinetic energy of the body due to translational
movement.
.. math::
E_{kt} = \frac{1}{2} m v^2
= \frac{1}{2} m \cdot v^\top v
:return: kinetic energy
:rtype: float
"""
mass = self.get_mass()
linear_vel = self.get_linear_velocity()
return mass * mut.dot_product(linear_vel, linear_vel) / 2.0
[docs] def calc_rotation_kinetic_energy(self):
r"""Calculate the kinetic energy of the body due to rotational
movement.
.. math::
E_{kr} = \frac{1}{2} I \omega^2 =
\frac{1}{2} \omega^\top \mathbf{I} \omega
:return: kinetic energy
:rtype: float
"""
It = self.get_inertia_tensor()
angular_vel = self.get_angular_velocity()
return mut.vector_matrix_vector(angular_vel, It) / 2.0
[docs] def calc_potential_energy(self, gravity):
r"""Calculate the potential energy of the body due to its position
(`x`) and the gravitational acceleration (`g`).
.. math::
E_p &= m \cdot g \cdot h = - m \cdot g^\top x
:param gravity: gravitational acceleration vector
:type gravity: tuple of 3 floats
:return: potential energy
:rtype: float
"""
mass = self.get_mass()
return -mass * mut.dot_product(gravity, self.get_position())
#==========================================================================
# Getters and setters
#==========================================================================
@property
def inner_object(self):
return self._inner_object
[docs] def get_attached_geom(self):
return self._attached_geom
@abstractmethod
[docs] def get_position(self):
"""Get the position of the body.
:return: position
:rtype: 3-sequence of floats
"""
pass
@abstractmethod
[docs] def get_linear_velocity(self):
pass
@abstractmethod
[docs] def get_rotation(self):
"""Get the orientation of the body.
:return: rotation matrix
:rtype: 9-sequence of floats
"""
pass
@abstractmethod
[docs] def get_angular_velocity(self):
pass
@abstractmethod
[docs] def get_mass(self):
pass
@abstractmethod
[docs] def get_center_of_gravity(self):
pass
@abstractmethod
[docs] def get_inertia_tensor(self):
pass
@abstractmethod
[docs] def set_position(self, pos):
"""Set the position of the body.
Sends :data:`signals.BODY_PRE_SET_POSITION` and
:data:`signals.BODY_POST_SET_POSITION`.
:param pos: position
:type pos: 3-sequence of floats
"""
pass
@abstractmethod
[docs] def set_rotation(self, rot):
"""Set the orientation of the body.
Sends :data:`signals.BODY_PRE_SET_ROTATION` and
:data:`signals.BODY_POST_SET_ROTATION`.
:param rot: rotation matrix
:type rot: 9-sequence of floats
"""
pass
[docs] def save_velocities(self):
"""Retrieve the actual velocities (linear and angular) of the body and
save them.
"""
self._saved_linear_vel = self.get_linear_velocity()
self._saved_angular_vel = self.get_angular_velocity()
[docs] def get_saved_velocities(self):
"""Return last saved velocities (linear and angular)."""
return self._saved_linear_vel, self._saved_angular_vel
#==============================================================================
# Bodies
#==============================================================================
[docs]class Box(Body):
__metaclass__ = ABCMeta
def __init__(self, size, *args, **kwargs):
super(Box, self).__init__(*args, **kwargs)
self._size = size
@property
def size(self):
return self._size
[docs]class Sphere(Body):
__metaclass__ = ABCMeta
def __init__(self, radius, *args, **kwargs):
super(Sphere, self).__init__(*args, **kwargs)
self._radius = radius
@property
def radius(self):
return self._radius
[docs]class Capsule(Body):
__metaclass__ = ABCMeta
def __init__(self, length, radius, *args, **kwargs):
super(Capsule, self).__init__(*args, **kwargs)
self._length = length
self._radius = radius
@property
def length(self):
return self._length
@property
def radius(self):
return self._radius
[docs]class Cylinder(Body):
__metaclass__ = ABCMeta
def __init__(self, length, radius, *args, **kwargs):
super(Cylinder, self).__init__(*args, **kwargs)
self._length = length
self._radius = radius
@property
def length(self):
return self._length
@property
def radius(self):
return self._radius
[docs]class Cone(Body):
__metaclass__ = ABCMeta
def __init__(self, height, radius, *args, **kwargs):
super(Cone, self).__init__(*args, **kwargs)
self._height = height
self._radius = radius
@property
def height(self):
return self._height
@property
def radius(self):
return self._radius