[Bug Report] Setting opacity causes object to disappear but shadow remains

[yijionglin]

Describe the bug

I tried to make an object transparent using PreviewSurfaceCfg(opacity=0.8), but it made the entire object disappear — although its shadow was still visible.

Steps to reproduce

Please try to provide a minimal example to reproduce the bug. Error messages and stack traces are also helpful.

One can use the tutorial's code to reproduce this easily. Change line 56 to 60 to:

cfg_cone = sim_utils.ConeCfg( radius=0.15, height=0.5, visual_material=sim_utils.PreviewSurfaceCfg(diffuse_color=(1.0, 0.0, 0.0), opacity=1), )

And then in the terminal run ./isaaclab.sh -p scripts/tutorials/00_sim/spawn_prims.py

System Info

• Commit: [b7004f]
• Isaac Sim Version: [5.0]
• OS: [Ubuntu 22.04]
• GPU: [RTX 5090]
• CUDA: [12.8]
• GPU Driver: [553.05]

Additional context

Add any other context about the problem here.

Checklist

• [x] I have checked that there is no similar issue in the repo (required)
• [x] I have checked that the issue is not in running Isaac Sim itself and is related to the repo

[RandomOakForest]

Thank you for posting this. The team will review.

[PeterL-NV]

Hi @yijionglin , we're aware of the issue and will prioritize a fix in future releases, thanks for the reporting!

[PeterL-NV]

Hi, This happens in the RTX-RealTime rendering mode, as a WAR, you can change to RTX-Interactive(Path Tracing) mode and the opacity setting will work.