creating_environment.md

How to build a custom environment

We provide a variety of templating tools to build an environment in a modular way. Here we break down the creation of SawyerLift to demonstrate these functionalities. The code cited (here) can be found in _load_model methods of classes SawyerEnv (creates the robot) and SawyerLift (creates the table) plus the code of TableTopTask.

Modeling

Here we explain step-by-step how to create a model of a manipulation task using our APIs.

Creating the world

All mujoco object definitions are housed in an xml. We create a MujocoWorldBase class to do it.

from robosuite.models import MujocoWorldBase

world = MujocoWorldBase()

Creating the robot

The class housing the xml of a robot can be created as follows

from robosuite.models.robots import Sawyer

mujoco_robot = Sawyer()

We can add a gripper to the robot by creating a gripper instance and calling the add_gripper method on a robot

from robosuite.models.grippers import gripper_factory

gripper = gripper_factory('TwoFingerGripper')
gripper.hide_visualization()
mujoco_robot.add_gripper("right_hand", gripper)

To add the robot to the world, we place the robot on to a desired position and merge it into the world

mujoco_robot.set_base_xpos([0, 0, 0])
world.merge(mujoco_robot)

Creating the table

We can initialize the TableArena instance that creates a table and the floorplane

mujoco_arena = TableArena()
mujoco_arena.set_origin([0.16, 0, 0])
world.merge(mujoco_arena)

Adding the object

For details of MujocoObject, refer to the documentation about MujocoObject, we can create a ball and add it to the world. It is a bit more complicated than before because we are adding a free joint to the object (so it can move) and we want to place the object properly

from robosuite.models.objects import BoxObject
from robosuite.utils.mjcf_utils import new_joint

object_mjcf = BoxObject()
world.merge_asset(object_mjcf)

obj = object_mjcf.get_collision(name="box_object", site=True)
obj.append(new_joint(name="box_object", type="free"))
obj.set("pos", [0, 0, 0.5])
world.worldbody.append(obj)

Simulation

Once we have created the object, we can obtain a mujoco_py model by running

model = world.get_model(mode="mujoco_py")

This is a mujoco_py MjModel instance than can then be used for simulation.

For example,

from mujoco_py import MjSim, MjViewer

sim = MjSim(model)
viewer = MjViewer(sim)
sim.data.ctrl[:] = [1,2,3,4,5]
sim.step()
viewer.render()

For details, refer to mujoco_py's documentation or look at our implementations in the environments.