Environments

Overview

We provide Environments that follow the OpenAI gym interface for applications such as reinforcement learning algorithms. Generally speaking, an Environment instantiates Scene, Object and Robot and import them into its Simulator. An Environment can also be interpreted as a task definition, which includes observation_space, action space, reward, and termination condition. Most of the code can be found here: gibson2/envs/locomotor_env.py.

Config

To instantiate an Environment, we first need to create a YAML config file. It will specifies a number of parameters for the Environment, such as which scenes, robots, objects to load, what the sensor specs are, etc. Exapmles of config files can be found here: examples/configs.

Here is one example: examples/configs/turtlebot_p2p_nav.yaml

# scene
scene: building
model_id: Rs
is_interactive: false
build_graph: true
load_texture: true
pybullet_load_texture: true
trav_map_resolution: 0.1
trav_map_erosion: 2

# robot
robot: Turtlebot
velocity: 1.0

# task, observation and action
task: pointgoal # pointgoal|objectgoal|areagoal|reaching
target_dist_min: 1.0
target_dist_max: 10.0
initial_pos_z_offset: 0.1
is_discrete: false
additional_states_dim: 4

# reward
reward_type: geodesic
success_reward: 10.0
slack_reward: -0.01
potential_reward_weight: 1.0
collision_reward_weight: -0.1
collision_ignore_link_a_ids: [1, 2, 3, 4]  # ignore collisions with these robot links

# discount factor
discount_factor: 0.99

# termination condition
dist_tol: 0.36  # body width
max_step: 500
max_collisions_allowed: 500
goal_format: polar

# sensor spec
output: [sensor, rgb, depth, scan]
# image
# ASUS Xtion PRO LIVE
# https://www.asus.com/us/3D-Sensor/Xtion_PRO_LIVE
fisheye: false
image_width: 640
image_height: 480
vertical_fov: 45
# depth
depth_low: 0.8
depth_high: 3.5
# scan
# Hokuyo URG-04LX-UG01
# https://www.hokuyo-aut.jp/search/single.php?serial=166
# n_horizontal_rays is originally 683, sub-sampled 1/3
n_horizontal_rays: 228
n_vertical_beams: 1
laser_linear_range: 5.6
laser_angular_range: 240.0
min_laser_dist: 0.05
laser_link_name: scan_link

# sensor noise
depth_noise_rate: 0.0
scan_noise_rate: 0.0

# visual objects
visual_object_at_initial_target_pos: true
target_visual_object_visible_to_agent: false

Parameters of this config file is explained below:

Attribute	Example Value	Expalanation
scene	building	which type of scene: [empty, stadium, building]
model_id	Rs	model_id for the building scene
is_interactive	false	whether the scene is interactive, only model_id in dataset/gibson_list supports interactivity
build_graph	true	whether to build traversability graph for the building scene
load_texture	true	whether to load texture into MeshRenderer. Can be set to false if RGB is not needed
pybullet_load_texture	true	whether to load texture into PyBullet, for debugging purpose only
trav_map_resolution	0.1	resolution of the traversability map. 0.1 means each pixel represents 0.1 meter
trav_map_erosion	2	number of pixels to erode the traversability map. trav_map_resolution * trav_map_erosion should be almost equal to the radius of the robot base
robot	Turtlebot	which type of robot, e.g. Turtlebot, Fetch, Locobot, etc
is_discrete	false	whether to use discrete action space for the robot
velocity	1.0	maximum normalized joint velocity. 0.5 means maximum robot action will actuate half of maximum joint velocities that are allowed in the robot URDF file
task	pointgoal	which type of task, e.g. pointgoal, objectgoal, etc
target_dist_min	1.0	minimum distance (in meters) between the initial and target positions for the navigation task
target_dist_max	10.0	maximum distance (in meters) between the initial and target positions for the navigation task
initial_pos_z_offset	0.1	z-offset (in meters) when placing the robots and the objects to accommodate uneven floor surface
additional_states_dim	4	the dimension of proprioceptive observation such as odometry and joint states. It should exactly match the dimension of the output of get_additional_states()
reward_type	geodesic	which type of reward: [geodesic, l2, sparse], or define your own
success_reward	10.0	scaling factor of the success reward
slack_reward	-0.01	scaling factor of the slack reward (negative because it should be a penalty)
potential_reward_weight	1.0	scaling factor of the potential reward
collision_reward_weight	-0.1	scaling factor of the collision reward (negative because it should be a penalty)
collision_ignore_link_a_ids	[1, 2, 3, 4]	collision with these robot links will not result in collision penalty. These usually are links of wheels and caster wheels of the robot
discount_factor	0.99	discount factor for the MDP
dist_tol	0.36	the distance tolerance for converging to the navigation goal. This is usually equal to the diameter of the robot base
max_step	500	maximum number of timesteps allowed in an episode
max_collisions_allowed	500	maximum number of timesteps with robot collision allowed in an episode
goal_format	polar	which format to represent the navigation goals: [polar, cartesian]
output	[sensor, rgb, depth, scan]	what observation space is. sensor means proprioceptive info, rgb and depth mean RGBD camera sensing, scan means LiDAR sensing
fisheye	false	whether to use fisheye camera
image_width	640	image width for the camera
image_height	480	image height for the camera
vertical_fov	45	camera vertial field of view (in degrees)
depth_low	0.8	lower bound of the valid range of the depth camera
depth_high	3.5	upper bound of the valid range of the depth camera
n_horizontal_rays	228	number of horizontal rays to simulate for the LiDAR
n_vertical_beams	1	number of vertical beams to simulate for the LiDAR. Currently iGibson only supports n_vertical_beams == 1
laser_linear_range	5.6	upper bound of the valid range of the LiDAR
laser_angular_range	240.0	angular range of the LiDAR (in degrees)
min_laser_dist	0.05	lower bound of the valid range of the LiDAR
laser_link_name	scan_link	the link name of the LiDAR sensor in the robot URDF file
depth_noise_rate	0.0	noise rate for the depth camera. 0.1 means 10% of the pixels will be corrupted (set to 0.0)
scan_noise_rate	0.0	noise rate for the LiDAR. 0.1 means 10% of the rays will be corrupted (set to laser_linear_range)
visual_object_at_initial_target_pos	true	whether to show visual markers for the initial and target positions
target_visual_object_visible_to_agent	false	whether these visual markers are visible to the agents

Task Definition

The main Environment classes (NavigateEnv and NavigateRandomEnv) that use the YAML config files can be found here: gibson2/envs/locomotor_env.py.

NavigateEnv provides an environment to train PointGoal navigation task for fixed locations. NavigateRandomEnv builds on top of NavigateEnv and includes a mechanism to randomly sample initial and target positions. Following the OpenAI gym convention, they can be readily used to train RL agents.

It’s also fairly straighforward to cusutomize your own environment.

• Inherit NavigateEnv or NavigateRandomEnv and reuse as much functionality as possible.

• Want to change the observation space? Modify load_observation_space, get_state and its helper functions.

• Want to change reward function? Modify get_reward.

• Want to change termination condition? Modify get_termination.

• Want to modify episode reset logic? Modify reset and reset_agent.

• Want to add additional objects or robots into the scene? Check out load_interactive_objects and load_dynamic_objects in NavigateRandomEnvSim2Real. If these are brand-new objects and robots that are not in iGibson yet, you might also need to change gibson2/core/physics/robot_locomotors.py and gibson2/core/physics/interactive_objects.py.

Examples

Static Environments

In this example, we show how to instantiate NavigateRandomEnv and how to step through the environment. At the beginning of each episode, we need to call nav_env.reset(). Then we need to call nav_env.step(action) to step through the environment and retrieve (state, reward, done, info).

• state: a python dictionary of observations, e.g. state['rgb'] will be a H x W x 3 numpy array that represents the current image

• reward: a scalar that represents the current reward

• done: a boolean that indicates whether the episode should terminate

• info: a python dictionary for bookkeeping purpose The code can be found here: examples/demo/env_example.py.

from gibson2.envs.locomotor_env import NavigateEnv, NavigateRandomEnv
from time import time
import numpy as np
from time import time
import gibson2
import os
from gibson2.core.render.profiler import Profiler

def main():
    config_filename = os.path.join(os.path.dirname(gibson2.__file__),
                                   '../examples/configs/turtlebot_demo.yaml')
    nav_env = NavigateRandomEnv(config_file=config_filename, mode='gui')
    for j in range(10):
        nav_env.reset()
        for i in range(100):
            with Profiler('Env action step'):
                action = nav_env.action_space.sample()
                state, reward, done, info = nav_env.step(action)
                if done:
                    print("Episode finished after {} timesteps".format(i + 1))
                    break

if __name__ == "__main__":
    main()

You actually have already run this in Quickstart!

Interactive Environments

In this example, we show how to instantiate NavigateRandomEnv with an interactive scene Placida. In this scene, the robot can interact with many objects (chairs, tables, couches, etc) by pushing them around. The code can be found here: examples/demo/env_interactive_example.py.

Customized Environments

In this example, we show a customized environment NavigateRandomEnvSim2Real that builds on top of NavigateRandomEnv. We created this environment for our CVPR2020 Sim2Real Challenge with iGibson. You should consider participating. :)

Here are the custimizations that we did:

• We added a new robot Locobot to gibson2/core/physics/robot_locomotors.py

• We added additional objects into the scene: load_interactive_objects in NavigateRandomEnvSim2Real

• We added dynamic objects (another Turtlebot) into the scene: reset_dynamic_objects and step_dynamic_objects in NavigateRandomEnvSim2Real

The code can be found here: gibson2/envs/locomotor_env.py and examples/demo/env_customized_example.py.