If a brush has one of its face marked with common/nodrawnonsolid, the whole brush becomes nonsolid
With q3map2 master, when a brush has faces marked with common/nodrawnonsolid
or common/nodraw
(which is also nonsolid for some reason), then the whole brush becomes nonsolid, even if the other faces are marked with solid textures.
In this example, the brush on the left has all its faces covered with the same texture and is solid (players can step and shoot on it).
The right brush has only one face marked with common/nodrawnonsolid
but is completely nonsolid (impossible to step on it and doesn't stop weapon projectiles).
This issue is also present on the latest NetRadiant-Custom release.
However with NetRadiant 1.5.0-20220628 (pre !193 (merged)), it doesn't occur and the right brush is solid (the whole brush can also be shot at).
This issue affects several stock Xonotic maps such as Fuse or SilentSiege (there are probably others) where items or players can fall through seemingly solid surfaces.
According to http://q3map2.robotrenegade.com/docs/shader_manual/q3map-surface-parameter-directives.html , this may actually be an intended behavior, but I'm not sure:
surfaceparm nonsolid
This attribute indicates a brush, which does not block the movement of entities in the game world. It applied to triggers, hint brushes and similar brushes. This affects the content of a brush.