Module `moog.physics.constant_speed`

Constant speed corrective physics.

The ConstantSpeed class is a physics object that forces sprites in specified layers to have constant speed. It is typically used as a corrective physics.

Expand source code

"""Constant speed corrective physics.

The ConstantSpeed class is a physics object that forces sprites in specified
layers to have constant speed. It is typically used as a corrective physics.
"""

from . import abstract_physics
import itertools
import numpy as np


class ConstantSpeed(abstract_physics.AbstractPhysics):
    """Constant speed physics class.
    
    Forces sprites in specified layers to have constant speed by normalizing
    their velocities.
    """

    def __init__(self, layer_names, speed):
        """Constructor.

        Args:
            layer_names: String or iterable of strings corresponding to layers
                in environment state. All sprites in these layers will have
                speed equal to `speed` argument.
            speed: Float. Sprite velocities will be normalized to have norm
                equal to this (or zero if their velocity is zero).
        """
        if not isinstance(layer_names, (list, tuple)):
            layer_names = [layer_names]
        self._layer_names = layer_names
        self._speed = speed

    def apply_physics(self, state, updates_per_env_step):
        """Apply the physics.
        
        Args:
            state: Environment state.
            updates_per_env_step: Int. Number of times the physics is applied
                per environment step.
        """
        sprites = [s for k in self._layer_names for s in state[k]]
        for s in sprites:
            norm_velocity = np.linalg.norm(s.velocity)
            if norm_velocity:
                s.velocity = self._speed * s.velocity / norm_velocity

Classes

class ConstantSpeed (layer_names, speed)

Constant speed physics class.

Forces sprites in specified layers to have constant speed by normalizing their velocities.

Constructor.

Args

layer_names: String or iterable of strings corresponding to layers in environment state. All sprites in these layers will have speed equal to speed argument.
speed: Float. Sprite velocities will be normalized to have norm equal to this (or zero if their velocity is zero).

Expand source code

class ConstantSpeed(abstract_physics.AbstractPhysics):
    """Constant speed physics class.
    
    Forces sprites in specified layers to have constant speed by normalizing
    their velocities.
    """

    def __init__(self, layer_names, speed):
        """Constructor.

        Args:
            layer_names: String or iterable of strings corresponding to layers
                in environment state. All sprites in these layers will have
                speed equal to `speed` argument.
            speed: Float. Sprite velocities will be normalized to have norm
                equal to this (or zero if their velocity is zero).
        """
        if not isinstance(layer_names, (list, tuple)):
            layer_names = [layer_names]
        self._layer_names = layer_names
        self._speed = speed

    def apply_physics(self, state, updates_per_env_step):
        """Apply the physics.
        
        Args:
            state: Environment state.
            updates_per_env_step: Int. Number of times the physics is applied
                per environment step.
        """
        sprites = [s for k in self._layer_names for s in state[k]]
        for s in sprites:
            norm_velocity = np.linalg.norm(s.velocity)
            if norm_velocity:
                s.velocity = self._speed * s.velocity / norm_velocity

Ancestors

AbstractPhysics
abc.ABC

Methods

def apply_physics(self, state, updates_per_env_step)

Apply the physics.

Args

state: Environment state.
updates_per_env_step: Int. Number of times the physics is applied per environment step.

Expand source code

def apply_physics(self, state, updates_per_env_step):
    """Apply the physics.
    
    Args:
        state: Environment state.
        updates_per_env_step: Int. Number of times the physics is applied
            per environment step.
    """
    sprites = [s for k in self._layer_names for s in state[k]]
    for s in sprites:
        norm_velocity = np.linalg.norm(s.velocity)
        if norm_velocity:
            s.velocity = self._speed * s.velocity / norm_velocity

Inherited members

AbstractPhysics:
- reset
- step
- updates_per_env_step