[bug] Incorrect urdf preview with the v0.9.4 pre-release version

[zichunxx]

(Please add appropriate labels)

• [ ] Windows: (Version)
• [x] Linux: (Dist/Version)
• [x] ROS 1: Dist
• [ ] ROS 2: Dist

v0.9.4 pre-release

Version: 1.80.1
Commit: 74f6148eb9ea00507ec113ec51c489d6ffb4b771
Date: 2023-07-12T17:22:25.257Z
Electron: 22.3.14
ElectronBuildId: 21893604
Chromium: 108.0.5359.215
Node.js: 16.17.1
V8: 10.8.168.25-electron.0
OS: Linux x64 5.15.0-76-generic snap

what is the bug

Incorrect preview for Kuka arm. Cannot see the arm with right color and model.

Repro steps

1. git clone https://github.com/ros-industrial/kuka_experimental.git
2. preview kuka_lbr_iiwa_support/urdf/lbr_iiwa_14_r820.urdf

expected behavior

[brennand]

I'm also having the same problem with the franka_panda arm. I'm using:

ubuntu 22.04
ROS2 humble.
v0.9.4 pre-release

https://github.com/NVIDIA-Omniverse/IsaacGymEnvs/blob/main/assets/urdf/franka_description/robots/franka_panda.urdf

I had to add a world link and base_link:

  <link name="world"/>
  <joint name="world" type="fixed">
    <parent link="world"/>
    <child link="base_link"/>    
  </joint>
  <link name="base_link"/>
  <joint name="base_joint" type="fixed">
    <parent link="base_link"/>
    <child link="panda_link0"/>    
  </joint>

Will there be a way to specify the base link?