This my try at the new "passes=o" option, coaxing Fractint *not* to plot all Mandelbrot orbits, but only those outside the set (aka the well-known Buddhabrot). The formula uses Hiram Berry's idea of a rectangular grid of starting points independent of the actual display window (however, the actual screen resolution is used to subdivide the rectangle into a grid - but there's an option to further subdivide those "pixels"). Another option allows to avoid plotting orbits below a given iteration threshold (that is, starting points too far away from the fractal's border). Warning, patience required ;-) On my ancient Pentium 233 MMX an 1024x768 image produced by this par took about 6 hours 40 minutes! Regards, Gerald --------------- Begin .par (amd frm:) ------------------- Buddhabrot {;Variation for passes=o ; reset=2004 type=formula formulafile=spezial.frm formulaname=BuddhabrotOrd passes=o corners=-2.2/1/-1.2/1.2 params=-2.2/1.2/3.2/-2.4/0/0/6.28/3/32/0 float=y maxiter=4610 outside=summ periodicity=0 colors=@gamma1.map } frm:BuddhabrotOrd {;Ordered subpixel grid ;passes=o, periodicity=no ;maxit > 2*(pixelgridnum^2)*(maxiter per orbit) ;------------------------------------------------------------ ;p1 : Starting corner of area-of-initial-points ;p2r: Extent of area-of-initial-points in real direction ;p2i: Extent of area-of-initial-points in imaginary direction ;p3 : Initial z (usually 0) ;p4r: Bailout ;p4i: Pixelgridnum (i.e.: 2 --> 2x2 subdivision ; --> 4 orbits per pixel) ;p5r: Minimum iterations ; (escaping orbits with less won't be plotted) ;------------------------------------------------------------ ; n = imag(p4), nm1 = n - 1 smax = scrnmax - (1,1)/n dx = real(p2)/real(smax), dy = flip(imag(p2)/imag(smax)) c = c0 = p1 + real(scrnpix)*dx + imag(scrnpix)*dy imax = floor((maxit-1)*0.5/sqr(n)) z = 999999, zz = p3 xi = yi = j = exit = plot = 0: IF (plot) j = j - 1 z = sqr(z) + c ELSE IF (p4 < |zz|) IF (p5 > j) j = 0 ELSE plot = 1 z = p3 ENDIF ELSEIF (imax <= j) j = 0 ELSE j = j + 1 zz = sqr(zz) + c ENDIF ENDIF IF (j <= 0) IF (xi < nm1) xi = xi + 1 ELSE xi = 0 yi = yi + 1 ENDIF IF (yi >= n) exit = 1 ELSE j = plot = 0 c = c0 + (xi*dx+yi*dy)/n z = 999999, zz = p3 ENDIF ENDIF exit == 0 } ----------------- End .par (amd frm:) ---------------------