You don't need to engineer it. In our lab tests we accidentially realized that one of our desktop computers was "invisible" to the Velodyne, because it had a bl

You don't need to engineer it. In our lab tests we accidentially realized that one of our desktop computers was "invisible" to the Velodyne, because it had a black case. Every material that is black could be a good candidate. I am wondering if the google cars do have a problem with cars that have a matte black finish (those PVC foils). But you have to keep in mind that they are not invisible in the real sense, because you get a hole in your scan where you don't have points in your pointcloud. This could be detected, because the Velodyne usually has many beams pointing downward which eventually would hit the road, but would leave a hole instead if there is an NIR absorbing material. And if you use sensor fusion, you can use a camera to check for dark colors in those areas that might help you to detect such cases