I know that this is kinda off-topic, but I figure the engineers and programmers check this page. I'm building a 3d printer using a Lego Mindstorms NXT kit, and I want to know if you have any ideas on turning a 3d file into usable input, as specifying each cross-section will be time consuming.

Well, this is rather off-topic, but anyways, you'll probably want to search online for a custom program that translates these 3D files into something you can use. You should probably use Google.

Thank you. I didn't know where else to post it, and the official forums have been shut down.

3D printers use a weird filesystem similar to turtle graphics, you have to start at the base, then go to each layer defining the cursor where to move, systems that generate 3d printer files can get extremely complex as to also work against gravity, best of luck to ya