At first I thought it was a general problem with static meshes, but after further investigation it seems like only the starter content shape meshes have this problem. I cannot query physical materials on them, neither by trace nor by collision. The physical material is always invalid. Weirdly enough all other meshes seem to work and it definitely worked in 4.6.
I attached a small sample project.
Hey FTC-
Thank you for bringing this issue to our attention. I have reported this bug to our internal tracking database (UE-9757) for further investigation by an engineer.
Cheers
Hi there, Currently, trace complex on the line trace must be enabled to get the hit physical material or “Use Complex as Simple” on the mesh must be enabled for collision settings. The reason why it works on other meshes is probably because they have “Complex as simple” collision enabled which always does a per-poly collision check.
While it does partially solve the problem it does not seem to be the only cause.
I experimented around further and when exporting and reimporting the mesh it works again, even though the collision complexity is still set to “Default”.
Also I imagine using only complex traces would have a significant impact.