Missing `ParticleFieldEmissive.mdl` blocks PhysicalAI-Robotics-NuRec rendering in Isaac Sim 5.1

[Jiaq1Fu]

Summary

Loading any USDZ from the official nvidia/PhysicalAI-Robotics-NuRec dataset (e.g. hand_hold-endeavor-livingroom/stage_particle.usdz) into Isaac Sim 5.1 fails to render the 3DGS layer because ParticleFieldEmissive.mdl is not shipped in any public NVIDIA distribution channel I could find.

Cross-refs (similar but distinct): #135, #399, #352, #622, discussion #565

Environment

Isaac Sim	5.1.0.0 (pip wheel and standalone zip — same result on both)
IsaacLab	2.3.2
OS	Ubuntu 24.04.3 LTS, kernel 6.17.0
GPU	NVIDIA RTX 5080 (Blackwell, sm_120), driver 590.48.01, CUDA 12.8
Dataset	nvidia/PhysicalAI-Robotics-NuRec (Oct 2025 release), hand_hold-endeavor-livingroom scene

Reproduction

pip install 'isaacsim[all,extscache]==5.1.0.0' --extra-index-url https://pypi.nvidia.com
# (or use the standalone zip — same result)
hf download nvidia/PhysicalAI-Robotics-NuRec --repo-type dataset \
  --include "hand_hold-endeavor-livingroom/*" --local-dir ./nurec_assets
# Open in GUI or via SimulationApp
isaacsim ./nurec_assets/hand_hold-endeavor-livingroom/stage_particle.usdz

Error (from Kit log)

[Error] [rtx.neuraylib.plugin] [MDLC:COMPILER] 1.0 MDLC comp error: C120 could not find module '::ParticleFieldEmissive' in module path
[Warning] [rtx.neuraylib.plugin] Loading MdlModule to DB (rtx_scope0) failed: ::ParticleFieldEmissive
[Error] [omni.hydra] Unable to find SdrShaderNode for prim: '/__Fabric_StageInfo/MaterialPool/mat_da33892f/Shader' with identifier: '8438785193887901532<ParticleFieldEmissive><mdl>'
[Error] [rtx.scenedb.plugin] Failed to create nrend renderer with error code 2

Viewport renders fully blank (the embedded mesh prim is also tagged visibility=invisible in mesh.usd, so even the collision proxy is hidden when the 3DGS renderer fails to take over).

What I already verified (so this isn't a setup issue on my end)

• --/UJITSO/geometry=true is set via SimulationApp(extra_args=[...]); Kit log confirms carb.ujitso.processor.geometry.plugin initializes successfully (per NuRec Headless Rendering — UJITSO Geometry Processor Not Loading in Python Mode (Isaac Sim 5.1.0) #565)
• libnrend.so is present in both omni.hydra.rtx and omni.kit.usd.mdl extension caches
• Kit's MDL search paths (per Kit log) include:
  • <install>/extscache/omni.replicator.core-*/mdl
  • <install>/kit/mdl/rtx
  • <install>/kit/mdl/rtx/iray
  • <install>/kit/mdl/core/Base
• ParticleFieldEmissive.mdl is not present in any of those directories, nor anywhere else inside the install (find <install> -name "ParticleFieldEmissive*" returns nothing)
• Also not in any public distribution I checked:
  • Isaac Sim 5.1 pip wheel — 311 MDLs, none match
  • Isaac Sim 5.1 standalone zip (~17 GB extracted) — same 311 MDLs
  • "Particle Systems Asset Pack" (159 MB) on the public Omniverse asset list — contains only particles.mdl for PhysX fluids, unrelated
  • Public Omniverse asset S3 bucket: recursive listing of Assets/Isaac/5.1/NVIDIA/Materials/ — no match
  • nv-tlabs/3dgrut open-source exporter — generates this exact reference (@ParticleFieldEmissive.mdl@, subIdentifier ParticleFieldEmissive) but doesn't ship the file
  • GitHub code search across isaac-sim, NVIDIA-Omniverse, nv-tlabs, NVIDIA orgs — zero matches

The USDZ shader prim:

def Shader "Shader"
{
    uniform asset info:mdl:sourceAsset = @ParticleFieldEmissive.mdl@
    uniform token info:mdl:sourceAsset:subIdentifier = "ParticleFieldEmissive"
    uniform token info:implementationSource = "sourceAsset"
}

The bare filename means Kit searches its MDL paths — but the file is not provided anywhere we can find.

Questions

1. Where is ParticleFieldEmissive.mdl supposed to come from? An asset pack, an undocumented extension, an internal Nucleus mirror?
2. If it requires the 140 GB isaac-sim-assets-complete-5.1.0.{001,002,003}.zip packs, please document that on the dataset card — currently the dataset README just says "drop the USDZ into Isaac Sim".
3. Will Isaac Sim 6.0's native ParticleField3DGaussianSplat pipeline (per @vick-yu in Error loading and rendering nurec volume: 'Failed to create nrend renderer' #135) supersede this and ship without the missing-MDL problem? If so, a workaround note in the dataset card would help users not chase a non-fixable bug in 5.1.

Why this matters

The dataset is NVIDIA's flagship robotics 3DGS sample. As shipped, it is effectively unusable by any user who installs Isaac Sim via the public channels (pip, standalone, container) without enterprise Nucleus access. Mesh-only fallback works for navigation/locomotion training but blocks vision-based RL on the photoreal layer.

Happy to provide the full Kit log or test on different configurations.

[PeterL-NV]

Hi, Thanks for reporting the issue! Particle field is not supported on Isaac Sim 5.1, and you can try the stage_volume.usdz, that should be able to load. If you want to load stage_particle.usdz, you'll need to update to Isaac Sim 6.0, it's supported there. We will update the dataset README to add the minimal required Isaac Sim version to load the assets. Let us know if you need further help.

[Jiaq1Fu]

Thanks for the quick response! We tested stage_volume.usdz with --/UJITSO/geometry=true (confirmed in Kit log that carb.ujitso.processor.geometry.plugin initializes successfully), but still got:

[Error] [rtx.scenedb.plugin] Failed to create nrend renderer with error code 2

Setup:

• Isaac Sim 5.1.0.0 (standalone, with --/UJITSO/geometry=true extra arg)
• RTX 5080 (Blackwell, sm_120), driver 590.48.01, CUDA 12.8
• Ubuntu 24.04

The same nrend failure now happens on both particle and volume USDZ, regardless of UJITSO. Per @vick-yu's note in #135 about RTX 3080 (Ampere) not being supported — could you confirm whether the 5.1 nrend renderer is Blackwell (sm_120 / RTX 50-series) compatible? If not, that would explain why both file types fail with the same error.

We'll wait for 6.0 GA either way. In the meantime can you add a note to the dataset card listing the supported GPU generations alongside the minimum Isaac Sim version? Would save a lot of debugging for users on non-Ada hardware.

Happy to share the full Kit log if useful.