How can you make plants non solid so you can walk through them(ex: tremor's giant plants)
And patches. (ex: hanging pipes)
And grates- how can I make bottom of grate invisible?
The plants are models so they won't be solid to begin with (unless you set a certain spawnflag).
I don't think patches are solid either, but I'll leave that for someone else to clarify.
Everything else is just using shaders with surfaceparm nonsolid.
Grates are done with shaders too.
the top side of patches are solid.
first, you could either have a shader for every texture that you want to be nonsolid. you could copy any grate shader. alternatively, you could use the nonsolid shader in /common. i think that if a brush is textured with nonsolid, everything inside of it is effected.