I saw this today in a blog post: http://web.mit.edu/persci/people/adelson/checkershadow_illusion.html

It's obviously visually astonishing, and my first thought was that it would make a great sample in inkscape, although perhaps not distributed without permission.

Unfortunately, I'm not yet able to make the basic perspective shapes in inkscape, much less the convincing visual illusion of shadow.

If any expert inkscape user with good perspective-, alpha- and gradient-fu wanted to try this one, it would make a one humdinger of a tutorial. Thanks.

(larger view) http://web.mit.edu/persci/people/adelson/images/checkershadow/checkershadow_...