Export as... Illustrator bug
I've discovered that when now using File: Export As... to export labels for 3D rendering, the preview is empty while the .png file does get made. This is different than the last version of Illustrator, where the preview window showed a thumbnail view of what it was exporting.
This is what I start with, a file where I've moved the extents of the artboard to the extents of the artwork I'm seeking to define as a label:

I then go to File: Export As... and set the product as a .png file with "Use Artboards" checked:

And here is the bug:

Because Illustrator does go ahead and produce the proper output despite the fact the preview feature is now broken:

With every new version of Illustrator I see bugs now. Yay for making it easier to use for scrapbooking moms!
