My level contain mdl models and hmp terrain. All work fine. When i create simple box with invisible flag(for creating unpassble areas). I see error Message CRITICAL ERROR E003 - no
visible blocks in map. I create another simple box without any flags. I don`t see error message, but my first block is invisible, and passble. How create unpassable areas on level? If i use invisible mdl models is this slower then use simple blocks?

"My level contain mdl s and hmp terrain. All work fine. When i create simple box with invisible flag(for creating unpassble areas). I see error Message CRITICAL ERROR E003 - no
visible blocks in map."

This means there is no level geometery visible. In order to do what i think you want to do, you can simply make a small cube with no flags set, (default visible) and hide it way under the level and terrain so you cant see it anyways.

Did you ever figure this out? I'm getting the same error...

Sorry to trouble you. Thanks for your time!

I use templates. I think right way is see flags in c_move function.