Module moog.physics.gravity

Gravity forces.

Expand source code 
"""Gravity forces."""

from . import abstract_force
import numpy as np


class DownGravity(abstract_force.AbstractNewtonianForce):
    """Force class for downwards gravity.
    
    This gravity acts to pull objects down, as if on Earth's surface.
    """

    def __init__(self, g=-1.):
        """Constructor.

        Args:
            g: Scalar. Gravitational constant.
        """
        self._g = g

    def _compute_forces(self, sprite):
        force = self._g * sprite.mass * np.array([0, 1])
        return (force,)


class Gravity(abstract_force.AbstractNewtonianForce):
    """Force class for gravity.
    
    This gravity acts between bodies in space.
    """

    def __init__(self, g=-1., symmetric=True):
        """Constructor.

        Args:
            g: Scalar. Gravitational constant.
            symmetric: Bool. Whether to apply the force to both sprites
                involved. If False, only applies force to the second sprite, the
                second argument to .step().
        """
        self._g = g
        self._symmetric = symmetric

    def _compute_forces(self, sprite_0, sprite_1):
        """Compute forces on sprite_0 and sprite_1."""
        diff = sprite_1.position - sprite_0.position
        dist = np.linalg.norm(diff)
        if dist == 0.:
            return np.zeros(2), np.zeros(2)
        force_direction = diff / dist
        force_magnitude = self._g * sprite_0.mass * sprite_1.mass * dist

        sprite_1_force = force_magnitude * force_direction

        if self._symmetric:
            sprite_0_force = -1 * sprite_1_force
        else:
            sprite_0_force = np.array([0., 0.])

        return sprite_0_force, sprite_1_force

Classes

class DownGravity (g=-1.0)

Force class for downwards gravity.

This gravity acts to pull objects down, as if on Earth's surface.

Constructor.

Args

g
Scalar. Gravitational constant.
Expand source code 
class DownGravity(abstract_force.AbstractNewtonianForce):
    """Force class for downwards gravity.
    
    This gravity acts to pull objects down, as if on Earth's surface.
    """

    def __init__(self, g=-1.):
        """Constructor.

        Args:
            g: Scalar. Gravitational constant.
        """
        self._g = g

    def _compute_forces(self, sprite):
        force = self._g * sprite.mass * np.array([0, 1])
        return (force,)

Ancestors

Inherited members

class Gravity (g=-1.0, symmetric=True)

Force class for gravity.

This gravity acts between bodies in space.

Constructor.

Args

g
Scalar. Gravitational constant.
symmetric
Bool. Whether to apply the force to both sprites involved. If False, only applies force to the second sprite, the second argument to .step().
Expand source code 
class Gravity(abstract_force.AbstractNewtonianForce):
    """Force class for gravity.
    
    This gravity acts between bodies in space.
    """

    def __init__(self, g=-1., symmetric=True):
        """Constructor.

        Args:
            g: Scalar. Gravitational constant.
            symmetric: Bool. Whether to apply the force to both sprites
                involved. If False, only applies force to the second sprite, the
                second argument to .step().
        """
        self._g = g
        self._symmetric = symmetric

    def _compute_forces(self, sprite_0, sprite_1):
        """Compute forces on sprite_0 and sprite_1."""
        diff = sprite_1.position - sprite_0.position
        dist = np.linalg.norm(diff)
        if dist == 0.:
            return np.zeros(2), np.zeros(2)
        force_direction = diff / dist
        force_magnitude = self._g * sprite_0.mass * sprite_1.mass * dist

        sprite_1_force = force_magnitude * force_direction

        if self._symmetric:
            sprite_0_force = -1 * sprite_1_force
        else:
            sprite_0_force = np.array([0., 0.])

        return sprite_0_force, sprite_1_force

Ancestors

Inherited members