Re: pm3d question

[Ethan A M. <merritt@u.washington.edu>]

On Sunday 20 November 2005 11:41 am, Johannes Zellner wrote:
>
> 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).

OK. Yes, I see the same difference in speed with isosamples set to 40.  
Although you can get a factor of roughly 4X back again by enabling 
HIDDEN3D_QUADTREE.

> 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,

I agree with all of that.
My question still remains, though:

Why not move the Z-sorting of quadrangles into the hidden3d code?

This will not magically do the full, correct, tests for
which quadrangles to clip. But it *will* mean that other objects
(labels, points, vectors) will be correctly obscured by the 
Z-sorted quadrangles, and vice versa. 


-- 
Ethan A Merritt
Biomolecular Structure Center
University of Washington, Seattle 98195-7742