[Bug Report] 'rgb_render' mode in MPE produces a black screen

[bergem1t]

Describe the bug

When calling env.render() on an MPE environment with rgb_array render mode, I get a black screen. I tested it with simple_v2 and 'simple_adversary_v2'. It does work with connect_four_v3.
It works for MPEs if I call the function draw(). draw() is called in render() for human but not rgb_array mode.

Code example

from pettingzoo.mpe import simple_v2
from matplotlib import pyplot as plt


env = simple_v2.env(render_mode='rgb_array')

env.reset()
#env.env.env.draw() <--- works if uncommented
plt.figure; plt.imshow(env.render())

System info

pip installed pettingzoo version 1.22.2
Windows 11
python 3.9.13

Additional context

No response

Checklist

• I have checked that there is no similar issue in the repo

[cibeah]

Hello,

I encountered the same issue. Indeed in the render method of SimpleEnv (mpe/_mpe_utils/simple_env.py, line 279) which serves as base class for other MPE envs, the numpy array for the rgb_array version is rendered as a screen grab of the pygame screen, but the image is only drawn on the screen when mode is human. Incidentally the screen grab function is called in all cases even when it seems not needed.

Code:

observation = np.array(pygame.surfarray.pixels3d(self.screen))
if self.render_mode == "human":
    self.draw()
    pygame.display.flip()
return (
    np.transpose(observation, axes=(1, 0, 2))
    if self.render_mode == "rgb_array"
    else None
)

Maybe we could have something like:

self.draw()
if self.render_mode == "rgb_array":
    observation = np.array(pygame.surfarray.pixels3d(self.screen))
    return np.transpose(observation, axes=(1, 0, 2))
if self.render_mode == "human":  
    pygame.display.flip()
return None

I can make a PR, but not sure if this is not already being fixed.

[WillDudley]

Hello,

I encountered the same issue. Indeed in the render method of SimpleEnv (mpe/_mpe_utils/simple_env.py, line 279) which serves as base class for other MPE envs, the numpy array for the rgb_array version is rendered as a screen grab of the pygame screen, but the image is only drawn on the screen when mode is human. Incidentally the screen grab function is called in all cases even when it seems not needed.

Code:

observation = np.array(pygame.surfarray.pixels3d(self.screen))
if self.render_mode == "human":
    self.draw()
    pygame.display.flip()
return (
    np.transpose(observation, axes=(1, 0, 2))
    if self.render_mode == "rgb_array"
    else None
)

Maybe we could have something like:

self.draw()
if self.render_mode == "rgb_array":
    observation = np.array(pygame.surfarray.pixels3d(self.screen))
    return np.transpose(observation, axes=(1, 0, 2))
if self.render_mode == "human":  
    pygame.display.flip()
return None

I can make a PR, but not sure if this is not already being fixed.

This isn't currently being fixed due to lack of resources - we'd greatly appreciate a PR :)