Nice image, but I guess you used some orbit trap or something, or did some tweak on the formula cause I can't get that checkerboards with this julia values.
You've guessed right. I used the point (0, 0) as an orbit trap.
I'm interested on how they are much like the patterns from the mandelbrot on reals formula (the white ones, near the symmetry line)
Good question. I don't see an obvious reason for the similarity.