Re: pm3d question

[Johannes Z. <joh...@ze...>]

On Sun, Nov 20, 2005 at 10:58:48AM -0800, Ethan A Merritt wrote:
[...]
> Have you figured out any reason why the "set hidden3d" 
> apparently runs much slower on your machines than on mine?

The comparison depends pretty much on the sampling rate. Try to run the
attached versions w/o ~/.gnuplot. (set sam 40; set iso 40). On my
machine the pm3d correctly ordered plots (tori.gpi) run approx.
4 times faster than the hidden3d version (tori_hl.gpi).

> If there really is a speed bottleneck in the code, I'd like
> to try to pin it down and fix it.  Then we can go back to
> discussing if there are any other drawbacks to merging your
> pm3d sort code with the general hidden3d capability.

I believe that this is not a "bottleneck" but it is more the fact that
it is really time consuming to do the correct hidden3d calculations.
It think sorting the pm3d quadrangles and the hidden3d code are two very
different approches: the hidden3d code has to calculate intersections of
surfaces for example and doesn't draw hidden line segments at all. The
pm3d code on the other hand draws all quadrangles: by sorting the
quadrangles those lying in front overwrite those drawn before.
It think the correct depth ordering for pm3d should be the default,
since it is not really time consuming and it will most likely produce
correct plots. The other pm3d methods (scans...) will produce likely
incorrect plots (depending on your data for example).

-- 
Johannes