Modify mesh rendering shader

edit

You could try adding something like this to your visual block in your SDF file, it seems like it changes the shader used when rendering the model. Specifically the "shader" block.

<material>
          <lighting>1</lighting>
          <script>
            <uri>file://media/materials/scripts/gazebo.material</uri>
            <name>Gazebo/Grey</name>
          </script>
          <shader type='pixel'>
            <normal_map>__default__</normal_map>
          </shader>
          <ambient>0.3 0.3 0.3 1</ambient>
          <diffuse>0.7 0.7 0.7 1</diffuse>
          <specular>0.01 0.01 0.01 1</specular>
          <emissive>0 0 0 1</emissive>
</material>