World#

class blueprints.World[source]#

Bases: WorldType, NodeThing

This class is available through the shortcut blueprints.World.

Most attribute descriptions are partially taken from Mujoco.

angle#

Either 'radian' or 'degree' (avoid if possible).

Type:

str

autolimits#

Indicating whether limits are used or not.

Type:

bool

contact#

Indicating whether collisions and contacts are ignored in the simulations physics.

Type:

bool

gravity#

Indicating whether gravity exists.

Type:

bool

integrator#

The name of the integrator use, see integrator for a detailed description.

Type:

str

viscosity#

The viscosity of the Worlds Things.

Type:

float

Attributes Summary

center

The center is computed to position the FreeCamera of the viewer (see World.view()).

size

The size is computed to sclae the FreeCamera of the viewer (see World.view()).

Methods Summary

attach(*items[, copy, background])

This method attaches *items to the parent Thing. If copy is set true, a copy of the items is created. If copy is set to false, the kinematic graph might no longer be a tree resulting in infinite loops or naming conflicts if the same item is included in the tree twice. All items of a specific type can be accessed via the types attribute.

build()

This method constructs the xml structure of the kinematic tree.

detach(*items)

This method is used to detach Things from the kinematic tree.

from_xml_string(string)

This method reconstructs a World from a Mujoco xml string.

step([n_steps, seconds, pbar])

Performs timesteps in the simmulation.

to_xml_string()

If not build, this method will first build the world, retrieve the XML string and then unbuild the world again.

unbuild()

Unbuilds the World to anable alterations.

view([callback])

Launches an interactive window of the Mujoco simulation.

Attributes Documentation

center#

The center is computed to position the FreeCamera of the viewer (see World.view()).

Returns:

The center of the World ignoring background Things.

Return type:

np.ndarray

size#

The size is computed to sclae the FreeCamera of the viewer (see World.view()).

Returns:

The size of the World ignoring background Things.

Return type:

np.ndarray

Methods Documentation

attach(*items, copy=False, background=False)[source]#

This method attaches *items to the parent Thing. If copy is set true, a copy of the items is created. If copy is set to false, the kinematic graph might no longer be a tree resulting in infinite loops or naming conflicts if the same item is included in the tree twice. All items of a specific type can be accessed via the types attribute.

Parameters:

  • *items (list[blue.ThingType]) – All items that are to be attached.

  • copy (bool, optional) – A flag indicating whether a copy of the items should be attached.

  • background (bool, optional) – A flag indicating whether the attached Things belong to the Worlds background.

Raises:

TypeError – If an item is not a valid child an error is raised.

Return type:

None

build()[source]#

This method constructs the xml structure of the kinematic tree. It is called before the World is converted to an xml string if any modification to it was done since the last build. It is not necessary for a user to call this method since it is implicitly called every time the build needs to be updated.

Return type:

None

detach(*items)[source]#

This method is used to detach Things from the kinematic tree. They are afterwards no longer present in this Worlds children attributes and their parent attribute will be set to None.

Parameters:

*items (list[ThingType]) – Things that are no longer children of this World can be passed, as long as their type is a valid type for children of World.

Raises:

TypeError – If the arguments to this function are not valid children types an error is raised.

Return type:

None

classmethod from_xml_string(string)[source]#

This method reconstructs a World from a Mujoco xml string. It currently only supports reading models, that exclusively consist of blueprints supported features. In a future version it will be extended to be compatible to all Mujoco models.

Parameters:

string (str) – The xml description of the Mujoco model.

Returns:

The reconstructed World.

Return type:

blue.WorldType

step(n_steps=1, seconds=None, pbar=False)[source]#

Performs timesteps in the simmulation. Exactly one argument must be given by the user. All cameras that are recording are taking images during the simulation at their respective times.

Parameters:

  • n_steps (int | None) – The number of steps to be taken

  • seconds (int | float | None) – The number of seconds to be simulated

  • pbar (bool)

Return type:

None

to_xml_string()[source]#

If not build, this method will first build the world, retrieve the XML string and then unbuild the world again. If the user calls this method repeatedly the world should probably be build first.

Returns:

The xml string representing the xml model used to launch Mujoco.

Return type:

str

unbuild()[source]#

Unbuilds the World to anable alterations. This discards the current Mujoco simulation.

Return type:

None

view(callback=<function World.<lambda>>)[source]#

Launches an interactive window of the Mujoco simulation.

Parameters:

callback (function) – The callback function is called after each timestep. The user can use this function to update World properties during the simulation.

Return type:

None

__init__(name='anonymous_model', autolimits=True, viscosity=0.0, timestep=0.002, integrator='implicit', cone='pyramidal', gravity=True, contact=True, angle='radian', texture=None, **kwargs)[source]#
Parameters:

  • name (str, optional) – The user specified name for the Actuator. In the case of a naming conflict the name will be altered by an enumeration scheme.

  • autolimits (bool, optional) – This attribute affects the behavior of attributes such as 'limited' (on <body-joint> 'forcelimited', 'ctrllimited', and 'actlimited' (on <actuator>). If True, these attributes are unnecessary and their value will be inferred from the presence of their corresponding 'range' attribute. If False, no such inference will happen: For a Joint to be limited, both limited=``True`` and range=``min max`` must be specified. In this mode, it is an error to specify a range without a limit.

  • timestep (float | int | None, optional) – Simulation time step in seconds. This is the single most important parameter affecting the speed-accuracy trade-off which is inherent in every physics simulation. Smaller values result in better accuracy and stability. To achieve real-time performance, the time step must be larger than the CPU time per step (or 4 times larger when using the RK4 integrator). The CPU time is measured with internal timers. It should be monitored when adjusting the time step.

  • viscosity (float | int | None, optional) – Viscosity of the medium. This parameter is used to simulate viscous forces, which scale linearly with velocity. In SI units the viscosity of air is around 0.00002 while the viscosity of water is around 0.0009 depending on temperature. Setting viscosity to 0 disables viscous forces. Note that the default Euler integrator handles damping in the Joints implicitly – which improves stability and accuracy. It does not presently do this with body viscosity. Therefore, if the goal is merely to create a damped simulation (as opposed to modelling the specific effects of viscosity), we recommend using joint damping rather than body viscosity, or switching to the implicit or implicitfast integrator.

  • cone (str, optional) – The type of contact friction cone. Elliptic cones are a better model of the physical reality, but pyramidal cones sometimes make the solver faster and more robust.

  • integrator (str, optional) – This attribute selects the numerical integrator to be used. Currently the available integrators are the semi-implicit Euler method 'Euler', the fixed-step 4-th order Runge Kutta method 'RK4', the Implicit-in-velocity Euler method 'implicit', and 'implicitfast', which drops the Coriolis and centrifugal terms.

  • gravity (bool, optional) – A flag indicating whether gravity exists. Be default the gravitational constant. is set to \(6.674 \times 10^{-11} N \frac{m^2}{kg^2}\).

  • contact (bool, optional) – If False, collisions and contacts are ignored in the simulations physics.

  • angle (str, optional) –

    The angle measure either 'radian' or 'degree'. .. warning:

    At the moment 'degree' is not supported for any manipulations. It is recommended to
only use 'degree' if no orientation manipulation is performed on the model! To convert
from degrees to radians use the multiplier :attr:`DEGREES_TO_RADIANS <blueprints.utils.geometry.DEGREES_TO_RADIANS>`

  • **kwargs – Keyword arguments are passed to super().__init__.

  • texture (SkyboxTextureType | None)

classmethod __new__(*args, **kwargs)#