For collada meshes alpha of multiple RobotModel interfere

[simonschmeisser]

We noticed today that adding a second RobotModel display (or derived MoveIt ones) with alpha = 0.2 changes the display of the primary RobotModel to also have transparency. This only happens for Collada meshes, not STL

I first enable one RobotModel with alpha = 1, the robot uses individual collada meshes while gripper and camera are stl meshes

now I enabled a second RobotModel where alpha=0.2 and it will (visually) override the value for both (the input field is not affected)

Notice how both robots now have alpha=0.2 except for the gripper and camera

I suspect this is due to non unique material names, any idea @rhaschke ?

Your environment

• OS Version: Ubuntu 18.04
• ROS Distro: Melodic
• RViz, Qt, OGRE, OpenGl version as printed by rviz:

  [ INFO] [1562941360.215562081]: rviz version 1.13.3
  

[ INFO] [1562941360.215614003]: compiled against Qt version 5.9.5
[ INFO] [1562941360.215624573]: compiled against OGRE version 1.9.0 (Ghadamon)
[ INFO] [1562941360.431414141]: Stereo is NOT SUPPORTED
[ INFO] [1562941360.432597198]: OpenGl version: 3 (GLSL 1.3).
```

[rhaschke]

Could you please check whether the issue was introduced in #1294, i.e. validate the version before this merge?

[simonschmeisser]

seems to have regressed after commit c7b2daa

I disabled some links from both RobotModels to show that two alpha values are supported