newton.solvers.SemiImplicitSolver#

class newton.solvers.SemiImplicitSolver(model, angular_damping=0.05, friction_smoothing=1.0, joint_attach_ke=1.0e4, joint_attach_kd=1.0e2)#

A semi-implicit integrator using symplectic Euler

After constructing Model and State objects this time-integrator may be used to advance the simulation state forward in time.

Semi-implicit time integration is a variational integrator that preserves energy, however it not unconditionally stable, and requires a time-step small enough to support the required stiffness and damping forces.

See: https://en.wikipedia.org/wiki/Semi-implicit_Euler_method

Example

solver = newton.solvers.SemiImplicitSolver(model)

# simulation loop
for i in range(100):
    solver.step(model, state_in, state_out, control, contacts, dt)

Methods

`__init__`(model[, angular_damping, ...])	Create a new Euler solver.
`integrate_bodies`(model, state_in, state_out, dt)	Integrate the rigid bodies of the model.
`integrate_particles`(model, state_in, ...)	Integrate the particles of the model.
`notify_model_changed`(flags)	Notify the solver that parts of the `Model` were modified.

Attributes

device

Get the device used by the solver.

__init__(model, angular_damping=0.05, friction_smoothing=1.0, joint_attach_ke=1.0e4, joint_attach_kd=1.0e2)#

Create a new Euler solver.

Parameters:

model (Model) – Model to use by this solver.
angular_damping (float, optional) – Angular damping factor to be used in rigid body integration. Defaults to 0.05.
friction_smoothing (float, optional) – Huber norm delta used for friction velocity normalization (see warp.math.norm_huber()). Defaults to 1.0.
joint_attach_ke (float, optional) – Joint attachment spring stiffness. Defaults to 1.0e4.
joint_attach_kd (float, optional) – Joint attachment spring damping. Defaults to 1.0e2.

step(model, state_in, state_out, control, contacts, dt)#

Simulate the model for a given time step using the given control input.

Parameters:

model (Model) – The model to simulate.
state_in (State) – The input state.
state_out (State) – The output state.
control (Control) – The control input. Defaults to None which means the control values from the Model are used.
contacts (Contact) – The contact information.
dt (float) – The time step (typically in seconds).

property device: Device#

Get the device used by the solver.

Returns:: The device used by the solver.
Return type:: wp.Device

integrate_bodies(model, state_in, state_out, dt, angular_damping=0.0)#

Integrate the rigid bodies of the model.

Parameters:

model (Model) – The model to integrate.
state_in (State) – The input state.
state_out (State) – The output state.
dt (float) – The time step (typically in seconds).
angular_damping (float, optional) – The angular damping factor. Defaults to 0.0.

integrate_particles(model, state_in, state_out, dt)#

Integrate the particles of the model.

Parameters:

model (Model) – The model to integrate.
state_in (State) – The input state.
state_out (State) – The output state.
dt (float) – The time step (typically in seconds).

notify_model_changed(flags)#

Notify the solver that parts of the Model were modified.

The flags argument is a bit-mask composed of the NOTIFY_FLAG_* constants defined in newton.core.types. Each flag represents a category of model data that may have been updated after the solver was created. Passing the appropriate combination of flags enables a solver implementation to refresh its internal buffers without having to recreate the whole solver object. Valid flags are:

Constant	Description
`NOTIFY_FLAG_JOINT_PROPERTIES`	Joint transforms or coordinates have changed.
`NOTIFY_FLAG_JOINT_AXIS_PROPERTIES`	Joint axis limits, targets, or modes have changed.
`NOTIFY_FLAG_DOF_PROPERTIES`	Joint DOF state or force buffers have changed.
`NOTIFY_FLAG_BODY_PROPERTIES`	Rigid-body pose or velocity buffers have changed.
`NOTIFY_FLAG_BODY_INERTIAL_PROPERTIES`	Rigid-body mass or inertia tensors have changed.
`NOTIFY_FLAG_SHAPE_PROPERTIES`	Shape transforms or geometry have changed.

Parameters:: flags (int) – Bit-mask of model-update flags indicating which model properties changed.