Hi Emre,
This unfortunate transparency issue is a side effect of the fundamental software architecture of BIMx Desktop Viewer and cannot be "fixed" easily. The goon news is that currently we are working on the BIMx Lab app (full functional big models with drawings on mobile) and the next release of the BIMx Web Viewer (full functional big models with drawings on the web) and later these technologies will be used to renew the BIMx Desktop Viewer too.
If you get BIMx Lab from Apple App Store you can see that this problem doesn't exist anymore in the new software architecture.
Regards,
Gyuri