Many years ago, the contemporary artist David Hockney argued that Vermeer and perhaps other old masters had uses some mirror tricks to do such a great job. At the time, I worked for Ricoh (an imaging company) and our Chief Scientist was David Stork, and one of the things we worked on back then was bringing up engineering/optics counter-arguments that Hockney's claims didn't make sense.
Now an inventor thinks he's solved the mystery, and there's a new documentary out that gets into all this - here's a link to the documentary, or you can read the Vanity Fair article for some more perspective.