Re: more graphics changes.

[Søren Hauberg]

Daniel J Sebald skrev:
> Søren Hauberg wrote:
> > John W. Eaton skrev:
> >
> > > It would be helpful to me if people who have been using the new
> > > graphics features could check that I haven't broken too many things.
> > > Please report any problems that you find to this list.
> >
> > Currently it's hard to do complex animations because they "flicker" a 
> > lot. To see what I'm talking about you can run the following code:
> >
> > N = 500;
> > iterations = 30;
> > x = linspace(0, 20*pi, N);
> > y = sin(x);
> >
> > figure(1)
> > for i = 1:iterations
> >   clf
> >   hold on
> >   for j = 1:N-1
> >     h = plot(x(j:j+1), y(j:j+1), 'o');
> >     set(h, "color", rand(1,3));
> >   endfor
> >   hold off
> >   drawnow # Needed until pause calls drawnow
> >   pause(0.5)
> > endfor
> >
> > The problem seems to be that "clf" calls "drawnow" which means that 
> > each iterations in the above code calls "drawnow" twice which causes 
> > the "flickering" (is that even a word). Things seem to work for me if 
> > I remove the call to "drawnow" in "clf" but since I don't know the 
> > internals of the system I don't know if that'll break anything.
>
> Yes, flickering is a word ("And moth-like stars were flickering out" -- 
> Yeats)...
Thanks, not only for the English lesson but also for the culture :-)

> For me, redraws take 11 seconds.  (I have a five year old system, but 
> still can't figure out why graphics is so slow.)
In complex plots there is a problem on the octave side. If I remove the 
call to drawnow in clf I get smooth but slow animations, so I guess 
gnuplot is fast enough.

> There is the possibility of doing GIF animations, but that's not 
> portable of course.
Yeah, that's what I currently do for complex animations. For more simple 
animations (which is what I most often need) the current system is good 
enough (once I remove the call to drawnow in clf, that is).

Søren