This document details the architecture used to implement backend clients and backend features.
To maintain consistency from one backend client to another and to promote
modularity, we make use of several interfaces. Any new backend client
should inherit from
make use of the
Methods for connecting, disconnecting, and generally managing the client state
are a part of the client, while any methods for planning, scene management or
kinematics are attached to the planner. Eventually, methods for
execution and control will be included in the
but for now, such methods and attributes will be left with the
PlannerInterface serves as a template for any client-specific
planner, providing default behavior for each of the
methods listed within. When a developer wishes to override any
of these defaults, they should make use of the appropriate backend
feature interface from
backends/interfaces.py. The file
interfaces.py consists of a collection of classes, any
implementation of which is callable through its
method. For example:
from compas.geometry import Frame
from compas_fab.backends.interfaces import InverseKinematics
def inverse_kinematics(self, robot,
# insert fancy code here
can be instantiated and called in the following manner:
calculate_example_ik = ExampleInverseKinematics()
frame = Frame([0, 0, 0], [1, 0, 0], [0, 1, 0])
ik_result = calculate_example_ik(robot, frame)
# or equivalently:
ik_result = calculate_example_ik.inverse_kinematics(robot, frame)
These backend feature interfaces exist in part to enforce a common
signature across all implementations of, say,
inverse_kinematics for greater end-user ease. Please adhere to the
types listed for the arguments and return values listed in the documentation
for the backend features as much as possible.
These interfaces as exist to allow mixing and matching of the backend
features of various clients to suit the performance and overhead
requirements of the end-user. To illustrate this last point, consider the
following example, where the backend of
ClientA is very efficient at
computing inverse kinematics and has no feature to plan motion, while the
ClientB is slow to compute inverse kinematics but can plan motion:
with ClientA() as client_a, ClientB() as client_b:
inverse_kinematics = ClientAInverseKinematics(client_a)
plan_motion = ClientBPlanMotion(client_b)
Here we can assign the inverse kinematics to be calculated by the backend
ClientA, while the motion planning is calculated by the backend of
ClientB. (We assume
ClientB inherit from
ClientInterface and that
ClientBPlanMotion inherit from
This package defines the interfaces required to integrate backends into the simulation, planning and execution pipeline of COMPAS FAB.
Interface for all backend clients.
Interface for all planners associated with a backend client.
Interface for a Planner's forward kinematics feature.
Interface for a Planner's inverse kinematics feature.
Interface for a Planner's plan motion feature.
Interface for a Planner's plan cartesian motion feature.
Planning scene interfaces
Interface for a Planner's get planning scene feature.
Interface for a Planner's add collision mesh feature.
Interface for a Planner's append collision mesh feature.
Interface for a Planner's remove collision mesh feature.
Interface for a Planner's add attached collision mesh feature.
Interface for a Planner's remove attached collision mesh feature.
Interface for a Planner's reset planning scene feature.