I think there was some confusion because there was an edit while replying. Sorry.
This is what I wanted to do.
As you say, the structures were the same so I would have thought that the material index would be obtained in the same way. Because I thought they were returning the same type of information.
But the Face Index is still 0. I’ve tried this with complex and simple collision on both the hitter and hit side, but nothing works. I don’t intend to use line tracing.