User activity

When exporting 3D model to BIMx with Global Ilumination activated, the process is so slow than is unusable. We need multithreading core for this process so that time for that export process is reduced eight, ten or more times.
I can't understand why we can do something so common like a stair that overlaps itself. I know you can do with two or more stair objects, but this is a tedious work and simply imposible in a stair made of steel extruded pieces with their intersection...