Module moog.physics.physics
Physics class.
The physics argument to ..environment.Environment is typically an instance of
the Physics class in this file.
Expand source code
"""Physics class.
The `physics` argument to ..environment.Environment is typically an instance of
the Physics class in this file.
"""
from . import abstract_physics
import itertools
import numpy as np
class Physics(abstract_physics.AbstractPhysics):
"""Force physics class."""
def __init__(self, *forces, updates_per_env_step=1, corrective_physics=()):
"""Constructor.
Examples of usage:
```python
friction_force = Friction(coeff_friction=1)
spring_force = Spring(equilibrium=0.3, spring_const=0.1)
collision_force = Collision(elasticity=0.5)
# Specify only friction on the avatar sprite(s)
force = (friction_force, 'avatar')
my_physics = Physics(force)
# Specify friction on the avatar and prey sprite(s)
force = (friction_force, ['avatar', 'prey'])
my_physics = Physics(force)
# Specify friction on avatar and springs between avatar and all prey
forces = (
(friction_force, 'avatar'),
(spring_force, 'avatar', 'prey'),
)
my_physics = Physics(*forces)
# Add collisions between all avatar/prey sprites and walls/neutrals
forces = (
(friction_force, 'avatar'),
(spring_force, 'avatar', 'prey'),
(collision_force, ['avatar', 'prey'], ['walls', 'neutrals']),
)
my_physics = Physics(*forces)
```
Args:
*forces: Iterable. Each element is a tuple (force_instance, *args)
where force_instance is an instance of
abstract_force.AbstractForce and *args has the same length as
the number of arguments of force_instance's step() method. Each
element of args may be either a string key of the environment
state or an iterable of such. This specifies all sprites to feed
into the force.
updates_per_env_step: Int. Number of physics applications per step
of the environment. A higher value means smoother physics but
slower runtime. This is fed into the individual forces so that
they can accomodate their force strength accordingly.
corrective_physics: Optional instance (or iterable of instances) of
abstract_physics.AbstractPhysics to be applied every step before
updating the sprite positions. This is typically used to apply
corrections to sprite velocities. For example, it can be used to
enforce rigid tethers between sprites.
"""
super(Physics, self).__init__(updates_per_env_step=updates_per_env_step)
self._forces = forces
if not isinstance(corrective_physics, (list, tuple)):
corrective_physics = [corrective_physics]
self._corrective_physics = corrective_physics
def reset(self, state):
for force in self._forces:
force[0].reset(state)
for corrective_physics in self._corrective_physics:
corrective_physics.reset(state)
def _args_to_iterables(self, args_iterables):
"""Converts all non-iterable elements to singleton tuples."""
args_iterables = [
x if isinstance(x, (tuple, list)) else (x,)
for x in args_iterables
]
return args_iterables
def apply_physics(self, state, updates_per_env_step):
"""Move the sprites according to the physics."""
# Update sprites based on forces
for (force, *args_iterables) in self._forces:
args_iterables = self._args_to_iterables(args_iterables)
# If args_iterables = [['avatar', 'prey'], ['walls', 'neutrals']],
# then
# args_combinations = [
# ['avatar', 'walls'],
# ['avatar', 'neutrals'],
# ['prey', 'walls'],
# ['prey', 'neutrals'],
# ]
args_combinations = itertools.product(*args_iterables)
for args in args_combinations:
for sprites in itertools.product(*[state[s] for s in args]):
force.step(
*sprites, updates_per_env_step=updates_per_env_step)
for corrective_physics in self._corrective_physics:
corrective_physics.apply_physics(state, updates_per_env_step)
# Move sprites based on their velocity
delta_t = 1. / updates_per_env_step
for layer in state:
for sprite in state[layer]:
sprite.update_pos_from_vel(delta_t=delta_t)Classes
class Physics (*forces, updates_per_env_step=1, corrective_physics=())-
Force physics class.
Constructor.
Examples of usage:
```python friction_force = Friction(coeff_friction=1) spring_force = Spring(equilibrium=0.3, spring_const=0.1) collision_force = Collision(elasticity=0.5) # Specify only friction on the avatar sprite(s) force = (friction_force, 'avatar') my_physics = Physics(force) # Specify friction on the avatar and prey sprite(s) force = (friction_force, ['avatar', 'prey']) my_physics = Physics(force) # Specify friction on avatar and springs between avatar and all prey forces = ( (friction_force, 'avatar'), (spring_force, 'avatar', 'prey'), ) my_physics = Physics(*forces) # Add collisions between all avatar/prey sprites and walls/neutrals forces = ( (friction_force, 'avatar'), (spring_force, 'avatar', 'prey'), (collision_force, ['avatar', 'prey'], ['walls', 'neutrals']), ) my_physics = Physics(*forces) ```Args
*forces- Iterable. Each element is a tuple (force_instance, args) where force_instance is an instance of abstract_force.AbstractForce and args has the same length as the number of arguments of force_instance's step() method. Each element of args may be either a string key of the environment state or an iterable of such. This specifies all sprites to feed into the force.
updates_per_env_step- Int. Number of physics applications per step of the environment. A higher value means smoother physics but slower runtime. This is fed into the individual forces so that they can accomodate their force strength accordingly.
corrective_physics- Optional instance (or iterable of instances) of abstract_physics.AbstractPhysics to be applied every step before updating the sprite positions. This is typically used to apply corrections to sprite velocities. For example, it can be used to enforce rigid tethers between sprites.
Expand source code
class Physics(abstract_physics.AbstractPhysics): """Force physics class.""" def __init__(self, *forces, updates_per_env_step=1, corrective_physics=()): """Constructor. Examples of usage: ```python friction_force = Friction(coeff_friction=1) spring_force = Spring(equilibrium=0.3, spring_const=0.1) collision_force = Collision(elasticity=0.5) # Specify only friction on the avatar sprite(s) force = (friction_force, 'avatar') my_physics = Physics(force) # Specify friction on the avatar and prey sprite(s) force = (friction_force, ['avatar', 'prey']) my_physics = Physics(force) # Specify friction on avatar and springs between avatar and all prey forces = ( (friction_force, 'avatar'), (spring_force, 'avatar', 'prey'), ) my_physics = Physics(*forces) # Add collisions between all avatar/prey sprites and walls/neutrals forces = ( (friction_force, 'avatar'), (spring_force, 'avatar', 'prey'), (collision_force, ['avatar', 'prey'], ['walls', 'neutrals']), ) my_physics = Physics(*forces) ``` Args: *forces: Iterable. Each element is a tuple (force_instance, *args) where force_instance is an instance of abstract_force.AbstractForce and *args has the same length as the number of arguments of force_instance's step() method. Each element of args may be either a string key of the environment state or an iterable of such. This specifies all sprites to feed into the force. updates_per_env_step: Int. Number of physics applications per step of the environment. A higher value means smoother physics but slower runtime. This is fed into the individual forces so that they can accomodate their force strength accordingly. corrective_physics: Optional instance (or iterable of instances) of abstract_physics.AbstractPhysics to be applied every step before updating the sprite positions. This is typically used to apply corrections to sprite velocities. For example, it can be used to enforce rigid tethers between sprites. """ super(Physics, self).__init__(updates_per_env_step=updates_per_env_step) self._forces = forces if not isinstance(corrective_physics, (list, tuple)): corrective_physics = [corrective_physics] self._corrective_physics = corrective_physics def reset(self, state): for force in self._forces: force[0].reset(state) for corrective_physics in self._corrective_physics: corrective_physics.reset(state) def _args_to_iterables(self, args_iterables): """Converts all non-iterable elements to singleton tuples.""" args_iterables = [ x if isinstance(x, (tuple, list)) else (x,) for x in args_iterables ] return args_iterables def apply_physics(self, state, updates_per_env_step): """Move the sprites according to the physics.""" # Update sprites based on forces for (force, *args_iterables) in self._forces: args_iterables = self._args_to_iterables(args_iterables) # If args_iterables = [['avatar', 'prey'], ['walls', 'neutrals']], # then # args_combinations = [ # ['avatar', 'walls'], # ['avatar', 'neutrals'], # ['prey', 'walls'], # ['prey', 'neutrals'], # ] args_combinations = itertools.product(*args_iterables) for args in args_combinations: for sprites in itertools.product(*[state[s] for s in args]): force.step( *sprites, updates_per_env_step=updates_per_env_step) for corrective_physics in self._corrective_physics: corrective_physics.apply_physics(state, updates_per_env_step) # Move sprites based on their velocity delta_t = 1. / updates_per_env_step for layer in state: for sprite in state[layer]: sprite.update_pos_from_vel(delta_t=delta_t)Ancestors
- AbstractPhysics
- abc.ABC
Methods
def apply_physics(self, state, updates_per_env_step)-
Move the sprites according to the physics.
Expand source code
def apply_physics(self, state, updates_per_env_step): """Move the sprites according to the physics.""" # Update sprites based on forces for (force, *args_iterables) in self._forces: args_iterables = self._args_to_iterables(args_iterables) # If args_iterables = [['avatar', 'prey'], ['walls', 'neutrals']], # then # args_combinations = [ # ['avatar', 'walls'], # ['avatar', 'neutrals'], # ['prey', 'walls'], # ['prey', 'neutrals'], # ] args_combinations = itertools.product(*args_iterables) for args in args_combinations: for sprites in itertools.product(*[state[s] for s in args]): force.step( *sprites, updates_per_env_step=updates_per_env_step) for corrective_physics in self._corrective_physics: corrective_physics.apply_physics(state, updates_per_env_step) # Move sprites based on their velocity delta_t = 1. / updates_per_env_step for layer in state: for sprite in state[layer]: sprite.update_pos_from_vel(delta_t=delta_t)
Inherited members