Minor Pixel Difference in RGB Camera Output Each Run

[3414395729]

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Isaac Sim Version

[√] 4.5.0
4.2.0
4.1.0
4.0.0
4.5.0
2023.1.1
2023.1.0-hotfix.1
Other (please specify):

Operating System

Ubuntu 22.04
[√] Ubuntu 20.04
Windows 11
Windows 10
Other (please specify):

GPU Information

• Model: NVIDIA GeForce RTX 4060 Ti
• Driver Version: 535.183.01

Topic Description

RGB camera output differs slightly between runs — possibly due to noise or rendering non-determinism.

Detailed Description

I’m using the RGB camera in Isaac Sim 4.5.0 on Ubuntu 20.04 with an RTX 4060 Ti.

Each time I run the same simulation setup, the RGB output image is slightly different — specifically, I observed a one-pixel value difference across runs.

I expected the RGB output to be deterministic since I didn’t change any parameters between runs.

Is this caused by simulated sensor noise, or is there some non-determinism in the rendering pipeline (e.g., RTX real-time or path tracing mode)?

Is there a way to make the RGB output fully deterministic across runs?

Thanks in advance!

[VickNV]

Thank you for providing a detailed description of the issue. To help us investigate further, could you please provide step-by-step instructions and any relevant files that demonstrate where you observe the difference?

[3414395729]

Thank you for your prompt reply!
I’ve observed that even when the scene remains static, images captured by the camera at different moments show slight variations. Specifically, individual pixel values differ by approximately 1-2 from frame to frame. This seems to indicate an element of randomness in the rendering process. I’m looking for a way to disable this randomness.
Below is the minimal code to reproduce this phenomenon:

import carb
import numpy as np
import hashlib

from omni.isaac.kit import SimulationApp
simulation_app = SimulationApp({"headless": False})
from omni.isaac.core import World
from omni.isaac.sensor import Camera


# from omni.isaac.nucleus import get_assets_root_path
# import carb.settings

# settings = carb.settings.get_settings()

# settings.set("/persistent/isaac/asset_root/default", "/media/tay/D/isaac_sim_asset/Assets/Isaac/4.5")

# assets_root_path = get_assets_root_path()
# if assets_root_path is None:
#     print("Error: Could not find Isaac Sim assets folder")
# else:
#     print(f"Assets root path: {assets_root_path}")

world = World(stage_units_in_meters=1.0)

world.scene.add_default_ground_plane()

camera = Camera(
    prim_path="/World/Camera",
    resolution=(640, 480),
    frequency=60,
    position=[0.0, -3.0, 1.0],  
    orientation=[0.0, 0.0, 0.0, 1.0]
)
camera.initialize()

world.reset()

for _ in range(20):
    world.step(render=True)

last_hash = None
for i in range(30):
    world.step(render=True)

    image = camera.get_rgb()
    if image is None:
        print(f"Frame {i}: No image received")
        continue

    mean_val = np.mean(image)
    print(f"Frame {i} image mean: {mean_val}")

    img_bytes = image.tobytes()
    hash_now = hashlib.md5(img_bytes).hexdigest()

    print(f"Frame {i} hash: {hash_now}")
    if last_hash is not None:
        if hash_now == last_hash:
            print("✅ Same as previous frame")
        else:
            print("❌ Different from previous frame")

    last_hash = hash_now

simulation_app.close()

[VickNV]

After checking with our team, minor pixel variations between runs are normal in GPU-accelerated rendering systems like Isaac Sim. If you could share how these variations affect your workflow, we can better understand.