MDL materials with measured BSDF in NVIDIA Isaac Sim

Omniverse Isaac Sim
1

Hello,

I have an issue with the use of MDL materials with measured BSDF (with a .mbsdf file) in Isaac Sim. When I try to apply such a material, it stays dark and I get the following warning:

[Warning] [rtx.mdltranslator.plugin] Invalid expression for surface.scattering.measurement in material example_measured_bsdf

This issue for example also occures with the “example_measured_bsdf” material in the tutorials.mdl file located at C:\Users\USERNAME\AppData\Local\ov\pkg\isaac_sim-2023.1.1\kit\exts\omni.mdl.usd_converter\omni\mdl\usd_converter\tests\data\mdl\nvidia\sdk_examples\tutorials.mdl , which comes with the installation of Isaac Sim.

I also did some tests with the function df::bsdf_measurement_isvalid() and it seems that it always returns False, also with the .mbsdf file of the above mentioned material.
Is it possible that MDL materials with measured BSDF are not supported in Isaac Sim?

Thank you very much and best regards

2

I found out, that the RTX-Real-Time and RTX-Interactive (Path Tracing) renderers probably are not able to handle MDL materials with measured BSDF. The Iray renderer can do so, but is not available by default in Isaac Sim (see Isaac Sim - Accurate (Iray) Renderer - #2 by rthaker ).