[Question]How to programmatically access all NVIDIA vMaterials materials in Isaac Lab using Python (beyond single .mdl files)?

[umeshnandargi]

Topic Description

Detailed Description

I’m using the Isaac Lab Python API and need to work with materials from the NVIDIA vMaterials library.The library contains around 315 .mdl files, but according to NVIDIA’s documentation (and what I see in the Isaac Sim GUI), it provides roughly 2,600 individual materials.

From my understanding, each .mdl file is a module that can export multiple material definitions, which explains the difference between the file count and the number of available materials.

In my Python script, I’m using the MdlFileCfg class to load materials. However, this class only accepts the MDL file path, not the specific exported material name inside that module.

My question is:

How can I programmatically access and use all 2,600 materials from the NVIDIA vMaterials library using the Isaac Lab Python API (without relying on the Isaac Sim GUI)?In other words, how can I enumerate all exported material definitions from each .mdl file and load them via MdlFileCfg?

Other info

Isaac Sim Version - 5.0.0

Operating System - Ubuntu 24.04

GPU Model - NVIDIA GeForce RTX 3090 Ti

Driver Version - 580.65.06

[umeshnandargi]

Hi all, I wanted to share a potential insight related to this issue based on my own investigation.

I looked into the function spawn_from_mdl_file in visual_materials.py in this file and noticed this snippet:

material_name = cfg.mdl_path.split("/")[-1].split(".")[0]
omni.kit.commands.execute(
    "CreateMdlMaterialPrim",
    mtl_url=cfg.mdl_path.format(NVIDIA_NUCLEUS_DIR=NVIDIA_NUCLEUS_DIR),
    mtl_name=material_name,
    mtl_path=prim_path,
    select_new_prim=False,
)

Right now, the API only accesses the material name by extracting it from the .mdl filename, which limits usage to one material per .mdl file. Since many .mdl files contain multiple material definitions, this prevents accessing materials beyond just the file name.

If the API exposed the ability to specify or access individual material names within an .mdl file (not just the file name), it could solve the issue of programmatically accessing all vMaterials in Isaac Lab, as referenced in the issue.

This enhancement would provide much more flexibility for users needing to work with the full range of materials inside .mdl files.

Happy to hear feedback or if anyone has ideas on how to extend the API accordingly.

[RandomOakForest]

Thank you for posting this. I'll move this post to our Discussions for follow up. Here is a summary that may be of help.

You can programmatically enumerate and load all 2,600+ materials from the NVIDIA vMaterials library in Isaac Lab by leveraging the MDL (Material Definition Language) introspection utilities provided by OmniKit and Omniverse MDL Python bindings. These bindings allow you to query all exported materials defined inside a .mdl module, beyond the single-material limitation of MdlFileCfg.

---

Enumerating Material Definitions from .mdl Files

Each .mdl file can export multiple material definitions. To list them all, use the MDL SDK API exposed via Omniverse through the omni.mdl or omni.material extensions. Below is a working approach that enumerates all materials in .mdl modules:

import omni.mdl
import os

mdl_module_manager = omni.mdl.get_mdl_module_manager()

# Path to the vMaterials directory (your local or Nucleus path)
vmat_root = "/NVIDIA/Materials/vMaterials_2"

materials = {}

for root, _, files in os.walk(vmat_root):
    for file in files:
        if file.endswith(".mdl"):
            mdl_path = os.path.join(root, file)
            module_name = mdl_path.replace(vmat_root, "").replace("/", "::").replace(".mdl", "")
            try:
                defs = mdl_module_manager.get_material_definitions_in_module(module_name)
                materials[module_name] = defs
            except Exception as e:
                print(f"Failed to query {module_name}: {e}")

print(f"Found {sum(len(v) for v in materials.values())} material definitions across {len(materials)} mdl modules.")

This code uses the get_material_definitions_in_module() function to list all exported materials from each .mdl module. Each item in defs is the material name that can be referenced programmatically (e.g., "::Aluminum::Anodized" or "::Wood::Oak_Polished").

---

Loading Specific Materials via Isaac Lab

Once you enumerate the names, you can load them directly using the CreateMdlMaterialPrim command and pass both the MDL file and the definition name:

import omni.kit.commands

mdl_path = "/NVIDIA/Materials/vMaterials_2/Metals/Aluminum.mdl"
definition = "::Metals::Aluminum_Polished"
prim_path = "/World/Materials/Aluminum_Polished"

omni.kit.commands.execute(
    "CreateMdlMaterialPrim",
    mtl_url=mdl_path,
    mtl_name=definition,
    mtl_path=prim_path,
    select_new_prim=False,
)

This explicitly references one of the multiple materials exported from the same module. You can adapt this pattern to load all enumerated materials into a dictionary or into USD prims dynamically.

---

Integrating with MdlFileCfg

Since MdlFileCfg (from isaaclab.sim.spawners.materials.visual_materials_cfg) only supports mdl_path, an enhancement layer can be introduced:

from isaaclab.sim.spawners.materials.visual_materials_cfg import MdlFileCfg

cfg = MdlFileCfg(
    mdl_path="{NVIDIA_NUCLEUS_DIR}/Materials/vMaterials_2/Metals/Aluminum.mdl",
)
cfg.mdl_name = "::Metals::Aluminum_Polished"  # Extend dynamically

Although this property does not yet exist officially, wrapping spawn_from_mdl_file with a small custom loader that adds mdl_name support can allow parsing full MDL names (file + export).