Hmm.. Yes, it happens with every snapshot. It's definitely related to the mac retina display. I found a workaround on the apple website in the meantime. You need to open cityengine in low-resolution mode when you want to export snapshots and then it works fine:
- Quit the application if it is currently open.
- In the Finder, choose Applications from the Go menu.
- In the Applications folder that opens, click the application's icon so it is highlighted.
- Choose Get Info from the File menu.
- Place a checkmark next to "Open in Low Resolution" to enable Low Resolution mode.
- Close the window and double click the Application to reopen it.Note: You may also contact the developer of the application to determine if they are offering an update to the application for the Retina display.
So I guess this means that you can't work in the high-resolution mode when you want to export snapshots. Fortunately the rest of the functionalities in CityEngine seem to work fine in both modes.
Thanks for your help!