I had this problem today with my SFM map:
If you have the same problem, don't worry the fix is quite simple.
This error was caused by a displacement that had a nodraw texture surface. Basically it was a nodraw brush made into a displacement.
To fix this, simply change the texture (should work) or destroy the nodraw displacement faces (this is what I did)
I'll just leave this here, if anyone else has this problem in the future.
If you have the same problem, don't worry the fix is quite simple.
This error was caused by a displacement that had a nodraw texture surface. Basically it was a nodraw brush made into a displacement.
To fix this, simply change the texture (should work) or destroy the nodraw displacement faces (this is what I did)
I'll just leave this here, if anyone else has this problem in the future.
