Bug: Plate pickup shaped reward never triggers in Overcooked environment

[HeavyCrab]

Description

The plate pickup shaped reward in the Overcooked environment (v1) is broken due to two bugs in jaxmarl/environments/overcooked/overcooked.py.

Bug 1: Incorrect dimension comparison (Line 617)

Current code:
plate_loc_layer = jnp.array(maze_map == OBJECT_TO_INDEX["plate"], dtype=jnp.uint8)
no_plates_on_counters = jnp.sum(plate_loc_layer) == 0
Problem:

• Compares against the entire 3D maze_map instead of just the object channel
• Since OBJECT_TO_INDEX["plate"] = 5 and COLOR_TO_INDEX["grey"] = 5, all walls [2, 5, 0] match on the color channel
• This causes no_plates_on_counters to always be False, completely disabling the reward

Bug 2: Wrong inventory scope (Line 611)

Current code:
num_plates_in_inv = jnp.sum(inventory == OBJECT_TO_INDEX["plate"])
Problem:

• Only counts plates held by the current agent, not all agents
• Should check total plates across all agents like OvercookedV2 does

[amacrutherford]

Hi, please consider submitting a PR! Overcookedv2 is now out so we recommend using that in research as it corrects issues with the v1 environment.