Using Isaac Sim Assets causes a 2+ minute delay in standalone scripts

Omniverse Isaac Sim
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1

Isaac Sim Version

4.5.0
4.2.0
4.1.0
4.0.0
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: GeForce RTX 3080 Laptop GPU
  • Driver Version: 550.90.07

Topic Description

Detailed Description

The first call to add_reference_to_stage for an asset in Isaac Sim Assets takes 2+ minutes, with subsequent calls completing almost instantly.

I expected caching to make time-to-first-asset faster in subsequent runs, however this 2+ minute delay happens every time I run the script.

I am aware that there is a known startup delay to compile shaders the first time you use an installation of Isaac Sim. This is an unrelated issue.

Steps to Reproduce

  1. Install Isaac Sim, following the official installation directions here:

    uv venv -p python@3.10
source .venv/bin/activate
uv pip install -U isaacsim[all,extscache]==4.5.0 --extra-index-url https://pypi.nvidia.com

  2. Save and run the following script and accept the EULA:

    from isaacsim import SimulationApp

simulation_app = SimulationApp({"headless": False})

import time
from isaacsim.core.api import World
from isaacsim.core.utils.stage import add_reference_to_stage
from isaacsim.storage.native import get_assets_root_path


print(f"{int(time.time())} - Starting")
world = World(stage_units_in_meters=1.0)
world.scene.add_default_ground_plane()

print(f"{int(time.time())} - Getting Assets Root Path")
assets_root_path = get_assets_root_path()
print(f"{int(time.time())} - Isaac Sim assets folder: {assets_root_path}")

print("Adding UR5e")
ur5e_asset_path = assets_root_path + "/Isaac/Robots/UniversalRobots/ur5e/ur5e.usd"
print(f"{int(time.time())} - Adding reference to stage: {ur5e_asset_path}")
add_reference_to_stage(usd_path=ur5e_asset_path, prim_path="/World/ur5e")
print(f"{int(time.time())} - Finished adding reference to stage")

print("Adding UR5")
ur5_asset_path = assets_root_path + "/Isaac/Robots/UniversalRobots/ur5/ur5.usd"
print(f"{int(time.time())} - Adding reference to stage: {ur5_asset_path}")
add_reference_to_stage(usd_path=ur5_asset_path, prim_path="/World/ur5")
print(f"{int(time.time())} - Finished adding reference to stage")

world.reset()
while simulation_app.is_running():
    world.step(render=True)

simulation_app.close()

    Output, showing 2min9s to call add_reference_to_stage the first time, while subsequent calls (in the same execution of the script) finish nearly instantly:

    ...
[7.271s] Simulation App Startup Complete
1754268037 - Starting
1754268038 - Getting Assets Root Path
1754268038 - Isaac Sim assets folder: https://omniverse-content-production.s3-us-west-2.amazonaws.com/Assets/Isaac/4.5
Adding UR5e
1754268038 - Adding reference to stage: https://omniverse-content-production.s3-us-west-2.amazonaws.com/Assets/Isaac/4.5/Isaac/Robots/UniversalRobots/ur5e/ur5e.usd
2025-08-04 00:42:47 [137,274ms] [Warning] [omni.usd] Warning: in _ReportErrors at line 2890 of /builds/omniverse/usd-ci/USD/pxr/usd/usd/stage.cpp -- Could not load sublayer @omniverse://isaac-dev.ov.nvidia.com/Isaac/Robots/UniversalRobots/ur5e/configuration/ur5e_robot_schema.usd@ of layer @https://omniverse-content-production.s3-us-west-2.amazonaws.com/Assets/Isaac/4.5/Isaac/Robots/UniversalRobots/ur5e/ur5e.usd@; skipping. (recomposing stage on stage @anon:0x575cefd4bbd0:World0.usd@ <0x575cfc44bdf0>)

1754268167 - Finished adding reference to stage
Adding UR5
1754268167 - Adding reference to stage: https://omniverse-content-production.s3-us-west-2.amazonaws.com/Assets/Isaac/4.5/Isaac/Robots/UniversalRobots/ur5/ur5.usd
1754268168 - Finished adding reference to stage
2025-08-04 00:42:49 [138,652ms] [Warning] [omni.hydra.scene_delegate.plugin] Calling getBypassRenderSkelMeshProcessing for prim /World/ur5e/base_link/visuals.proto_mesh_id0 that has not been populated
[147.334s] Simulation App Shutting Down

  3. Run the script again, and observe it still takes 2+ minutes when adding the first asset to the stage.

Additional Information

What I’ve Tried

  • Enabling the Cache Status Indicator extension (omni.kit.widget.cache_indicator) shows CACHE: ON in the top right corner of the window.
  • The isaacsim.asset.browser extension complains about the lack of the requests module, but installing it has no effect on this issue.
  • I tried downloading and using the local Isaac Sim Assets Pack, but that created a separate set of issues that I may make a separate post about.
2

To avoid the delay from streaming assets, you can download the Isaac Sim asset packs and run them locally. The Assets section of the Setup Tips documentation provides instructions on how to set this up.

3

Thanks for your response VickNV.

Once I sit through the 2 minute wait, I can add new assets to the stage within seconds (including ones I have never used before). This seems to me like it is therefore not a delay caused by streaming the assets, but rather from a timeout, especially as it is an extremely consistent 2min10sec ± 2sec.
In fact, after the first time downloading a robot (which only takes 3-5 seconds), I can add it to the stage in less than a second, which indicates to me that my caching hypothesis was wrong and it is caching the downloads, and that the 2+ minute delay is unrelated to downloads/caching.

I will try the local asset packs again, but as I mentioned I already had issues with those, so I will either create a separate post about those issues tomorrow if I am still having them, or update you here if they work.

Thanks again,
Rory

4

The issue I had with the local Isaac Sim Assets Pack turned out to be out-of-date UR5e and UR3e files, which do not have their articulations set up correctly in the pack, but the amazonaws.com counterparts are correct. I manually downloaded and replaced the broken files with the ones from amazonaws.com to get our scripts running.

I never did manage to figure out how to solve the 2+ minute delay for the amazonaws.com assets, so we will continue using the local Isaac Sim Assets Pack until it gets solved.

5

Thank you for updating. Please help check if the issue is still with the latest Isaac Sim Assets on Download Isaac Sim — Isaac Sim Documentation.

We will look into the 2+ minute delay and update with our findings.

7

Please try running with -vv flag and see if any culprit messages.

8

Hello!

We noticed that this topic hasn’t received any recent responses, so we are closing it for now to help keep the forum organized.

If you’re still experiencing this issue or have additional questions, please feel free to create a new topic with updated details. When doing so, we recommend mentioning or linking to this original topic in your new post—this helps provide context and makes it easier for others to assist you.

Thank you for being part of the NVIDIA Isaac Sim community.

Best regards,
The NVIDIA Isaac Sim Forum Team