This is my imported model. It is converted from .obj file. I was trying to convert .dxf, .stl, .igs and .obj files. Extensions which have been working properly was only .obj and .dxf. Conversion of these files was smooth and easy. However I had some troubles with .stl and .igs files: .stl files couldn't even convert succesfully, there were a lot of errors in command prompt and in a result converted model didn't work. On the other hand .stl files converted perfectly and without any errors but when I opened a model in BRL-CAD and was trying to draw something, nothing was appearing. After typing "tops" nothing was happening. So I converted only .obj file and it works great! :)