Rich, Periodicity checking is just one of the options affected by "incorrectly" using the z variable. This par is a great example. It uses inside=bof61, which colors the inside pixels based on the value of min_index. The value of min_index is determined by: if (magnitude < min_orbit) { min_orbit = magnitude; min_index = coloriter + 1; } So, anything that changes the value of magnitude, will change the value of min_index. Magnitude is calculated for the formula type with: magnitude = sqr(new.x) + sqr(new.y); Where new.x is obtained from z.x and new.y is obtained from z.y. If the way z is used in the formula is changed, the image is going to change. The only safe options are inside=numb, inside=iter, outside=numb, and outside=iter. All other inside and outside options use new.x and/or new.y. The distance estimator, potential, and biomorph options also use new.x and new.y. So, it is possible to create images that won't be affected by fixing this formula. But for currently existing parameter sets, odds are, more images will be broken than remain the same. Jonathan
Yes, that is correct. This would fix the formula and probably break any images previously generated with it.
OK, the first part I understand, but I don't understand why this would break any images previously generated. Or did you mean that it would break any previously generated image that erroneously used periodicity checking? If periodicity checking was off (as it was on this parset for the FOTD), then I would expect the image to be the same.