Thank you, Everyone! This is a pattern from Ricky Tims' (sorry misspelled it in my title!) book Convergence Quilts, Mysterious, Magical, Easy, and Fun published in 2003. He gave some useful pointers for picking and placing fabrics in this type of design. It may be out of print by now, but as Kitsie says above, the pattern is still available. I wonder what took me so long. There are versions in the book using curves, and someday maybe I'll get around to that, too. These designs are so innovative without being difficult. I wonder what my grandmother would have thought of it.