Gazebo how to read mesh material with sensor

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Hi all,

I have a 3d semantic model of a large-scale environment. That is, an .obj file with the scene geometry along with the .mtl file where the materials are the face labels (e.g. ceiling,floor,wall,etc...). I imported it into gazebo by converting the obj file into dae and I'm able to visualize it correctly. What I would like to do now is to read for each face of the mesh, currently in the field of view of the camera mounted on a robot, the corresponding label. Can someone please show me how this can be done?

Thanks!

Federico