SherLock<brewhaha@freenet.edmonton.ab.ca> commented earlier:
On Wed, 17 Nov 2004, Hiram Berry wrote:
I understand that the periodicity=0 option is supposed to not plot orbits that go off the screen or bailout.
No. Going off the screen has nothing to do with it. And you CAN'T plot points that go off the screen (consider the virtual screen to be real, because it does take space in your video RAM).
While I can imagine a facility where you _could_ plot offscreen points to a virtual screen buffer(linked list of points or some such), which in a trivial sense the disk modes do, that isn't exactly what I was referring to. To clarify, note that I said "orbits", not "points". "orbit" = set of points, and going off the screen does apparently have something to do with the rendering with {passes=o,periodicity={on||off}} at least if the fractint.doc file is to be believed; to quote from the section on passes=o: A non-zero value of the "periodicity=" option causes Orbits to not plot orbits that have reached the bailout conditions or where an orbit goes off the visible area of the image. A zero value of periodicity will plot all orbits except as modified by orbitdelay and orbitinterval. [snip good explanation of normal operation of periodicity checking}
It is more effective in saving time at high iteration counts. Yes, but we're concerned here only with its behavior with the "passes=o" option, which seems to be a little different than when other drawing methods are used. The problem is that if periodicity checking is turned on, and it behaves as quoted above, some inside orbits may contain points that are offscreen, and if I interpret the quote correctly it means none of the points in that particular orbit will be plotted. Union a set of orbits which behave similarly, and entire subobjects of the orbit set (eg. orbit-space images of the buds of the M-set) may disappear from the image. To me, the orbit image of the M-set is an interesting object in its own right, visually different from the M-set and worthy of exploration without parts of it vanishing, so it seems that I have to use the periodicity=0 setting to get an accurate rendering.
Also, having benchmarked the periodicity options with passes=o, I didn't find much difference in the render times between on and off, so it appears that the actual periodicity checking mechanism is turned off when invoked from the passes=o mode. ---Hiram