My sister does line art and I was curious if the Glowforge tracing feature can follow the lines if the art piece itself is placed under glass/plastic?
I know you can scan them into the computer and all, but being able to just set a clear piece over one of her black and white drawings and starting it would be cool.
Are you wanting to etch the glass or clear acrylic with the design?? Not sure how the optics will work through those, but you could copy it to a piece of paper and put it on top…then have the trace feature engrave through it I suppose…
Yeah, and that is what I was wondering if the optics can do that. It would really cut down on waste for what I have planned.
I do not believe that glass or acrylic are transparent at the frequencies the Glowforge operates at, so the artwork should be safe from the laser. The optics they are using to grab the image should be able to see through them fairly easily. My guess would be you shouldn’t have an issue with it. Or you could have your sister draw right onto the glass. 
We have lots of work to do on the image manipulation software so I won’t hazard a guess as to how well this will work when we’re done, but it seems possible.
If the Glowforge can’t scan through the glass/plastic, you could probably have the Glowforge scan artwork while it is on top of the glass/plastic and then remove the artwork before starting the print.