>>>>> "Darren" == Darren Dale <dd...@co...> writes: Darren> I just noticed that the following script generates a Darren> diagonal line that looks like it was drawn with a really Darren> unsteady hand: Darren> from pylab import frange, plot, show Darren> plot(frange(-1,1,.01)*1e10) show() Darren> The problem is not noticable for a small number of points, Darren> such as plot(frange(-1,1,.5)*1e10). I tried clearing Darren> site-packages, rebuilt MPL-0.80, the problem appears to be Darren> in CVS. w/o testing, I'll hazard a guess that this is due to a workaround I have never been able to figure out with how agg does subpixel rendering Try commenting out these lines in _backend_agg.cpp in the draw_lines function thisx = (int)thisx + 0.5; thisy = (int)thisy + 0.5; These lines snap all the x and y points to pixel centers. If you don't use pixel centers, agg will draw lines of different widths and heights depending on the subpixel fraction. This is only apparent for vertical and horizontal lines, generally, but is glaring for ticks and grid lines. In the past, I've added a hack to only do snap to pixel for horizontal and vertical lines with 2 points, which fixes the special case problems of ticks and grids I raised this issue with Maxim on the agg mailing list http://sourceforge.net/mailarchive/message.php?msg_id=8575544 and he responded by writing this page http://antigrain.com/tips/line_alignment/line_alignment.agdoc.html which I still haven't been able to digest sufficiently in a way that fixes this problem generally. I reinstated in CVS a temporary hack which only does the snapto pixel trick for len(2) lines. Should work well for most use cases. Give it a try. JDH