environment gif

This environment is part of the sisl environments. Please read that page first for general information.

Import from pettingzoo.sisl import multiwalker_v7
Actions Continuous
Parallel API Yes
Manual Control No
Agents agents= ['walker_0', 'walker_1', 'walker_2']
Agents 3
Action Shape (4,)
Action Values (-1, 1)
Observation Shape (31,)
Observation Values [-inf,inf]
Average Total Reward -300.86

Agent Environment Cycle

environment aec diagram


In this environment, bipedal robots attempt to carry a package as far right as possible. A package is placed on top of 3 (by default) bipedal robots which you control. A positive reward is awarded to each walker, which is the change in the package distance summed with 130 times the change in the walker’s position. By default, the environment is done if any walker or the package falls. A walker is given a reward of -100 when they fail the game by either condition. If the walker falls, they are penalized an additional -10. If the terminate_on_fall setting is set to false, the game continues until the package falls. If the remove_on_fall setting is set to True, the walkers are removed from the scene after they fall. If the global reward mechanic is chosen, the mean of all rewards is given to each agent. Each walker exerts force on two joints in their two legs, giving a continuous action space represented as a 4 element vector. Each walker observes via a 31 element vector containing simulated noisy lidar data about the environment and information about neighboring walkers. The environment’s duration is capped at 500 frames by default (can be controlled by the max_cycles setting).

Observation Space

Each agent receives an observation composed of various physical properties of its legs and joints, as well as LIDAR readings from the space immediately in front and below the robot. The observation also includes information about neighboring walkers, and the package, which have normally distributed signal noise controlled by position_noise and angle_noise. For walkers without neighbors, observations about neighbor positions are zero.

This table enumerates the observation space:

Index: [start, end) Description Values
0 Hull angle [0, 2*pi]
1 Hull angular velocity [-inf, inf]
2 X Velocity [-1, 1]
3 Y Velocity [-1, 1]
4 Hip joint 1 angle [-inf, inf]
5 Hip joint 1 speed [-inf, inf]
6 Knee joint 1 angle [-inf, inf]
7 Knee joint 1 speed [-inf, inf]
8 Leg 1 ground contact flag {0, 1}
9 Hip joint 1 angle [-inf, inf]
10 Hip joint 2 speed [-inf, inf]
11 Knee joint 2 angle [-inf, inf]
12 Knee joint 2 speed [-inf, inf]
13 Leg 2 ground contact flag {0, 1}
14-23 LIDAR sensor readings [-inf, inf]
24 Left neighbor relative X position (0.0 for leftmost walker) (Noisy) [-inf, inf]
25 Left neighbor relative Y position (0.0 for leftmost walker) (Noisy) [-inf, inf]
26 Right neighbor relative X position (0.0 for rightmost walker) (Noisy) [-inf, inf]
27 Right neighbor relative Y position (0.0 for rightmost walker) (Noisy) [-inf, inf]
28 Walker X position relative to package (0 for left edge, 1 for right edge) [-inf, inf]
29 Walker Y position relative to package [-inf, inf]
30 Package angle [-inf, inf]


multiwalker_v7.env(n_walkers=3, position_noise=1e-3, angle_noise=1e-3,
local_ratio=1.0, forward_reward=1.0, terminate_reward=-100.0, fall_reward=-10.0,
terminate_on_fall=True, remove_on_fall=True, max_cycles=500)

n_walkers: number of bipedal walker agents in environment

position_noise: noise applied to agent positional sensor observations

angle_noise: noise applied to agent rotational sensor observations

local_ratio: Proportion of reward allocated locally vs distributed among all agents

forward_reward: reward applied for an agent standing, scaled by agent’s x coordinate

fall_reward: reward applied when an agent falls down

terminate_reward: reward applied to a walker for failing the environment

terminate_on_fall: toggles whether agent is done if it falls down

remove_on_fall: Remove walker when it falls (only does anything when terminate_on_fall is False)

max_cycles: after max_cycles steps all agents will return done

Version History

  • v7: Fixed problem with walker collisions (1.8.2)
  • v6: Fixed observation space and made large improvements to code quality (1.5.0)
  • v5: Fixes to reward structure, added arguments (1.4.2)
  • v4: Misc bug fixes (1.4.0)
  • v3: Fixes to observation space (1.3.3)
  • v2: Various fixes and environment argument changes (1.3.1)
  • v1: Fixes to how all environments handle premature death (1.3.0)
  • v0: Initial versions release (1.0.0)