oh, thanks michael. i didn't even know i was missing out on something cool. i'm glad i asked. i haven't used adobe's viewer in, oh, maybe two decades. i didn't know it still existed, lol.
After I read your comments I checked and apparently I'm still using 15 year old software from 2008 (Adobe Acrobat 9 Pro Extended).
Time flies when you're having fun.
If you have an Android phone/device, 3D PDF Reader (Tech Soft 3D), has worked pretty well for me. Not sure about iOS, as I don't have it.
thanks a lot for this information. i'm using android. however, i opened your file on windows. in that case, i'm using Firefox. it seemed like the adobe reader wasn't really needed anymore. at least over a decade ago. i guess they added 3d pdf. which i didn't know about. so learned something new.
The transparent glass was done in Acrobat 9 Pro Ext., it allows you to pick individual objects and specify solid, solid outline, transparent, solid wire frame, illustration, shaded illustration etc.