Re: Plot order with pm3d?

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

On Thursday 21 February 2008 18:04, Philipp K. Janert wrote:
> 
> According to the documentation to pm3d,
> "when plotting several plots, they are plotted in
> the order given on the command line"

Yes, but that only applies to pm3d plots.
 
> So, I would expect that the following two plots
> would appear different:
> 
> set pm3d explicit
> splot [-2:2][-2:2] exp(-x**2-y**2) w pm3d, 2-exp(-x**2-y**2) 
> splot [-2:2][-2:2] 2-exp(-x**2-y**2), exp(-x**2-y**2) w pm3d
> 
> Note that I switch the order of the functions between
> both calls, but want the same function drawn with pm3d.

You are mixing pm3d and non-pm3d plots, which as you have
discovered raises an issue of what gets drawn first.
Further complicating the issue is that pm3d and non-pm3d
plots have separate options for depth ordering, which _also_
affects what gets drawn first.

> But, both plots appear to be the same.
> 
> Which is annoying, because I don't seem to be able
> to get the transparent (wiremesh) function visually
> on top of the opaque surface. 

 
> Is this a bug or a feature?

I think it's a design flaw;  with perfect foresight pm3d would
have been more integrated with other plot types, rather than 
acting as a parallel subsystem.  However, there are work-arounds.
In particular, see the first plot of the hidden2 demo:
   http://gnuplot.sourceforge.net/demo_4.3/hidden2.html

> In a similar spirit, I noticed that when setting
> set pm3d (or set pm3d explicit) the surface hides
> the border, but when using set pm3d implicit, the
> border is always on top of the surface - even when
> setting set border back.

I have noticed that also, or something very similar.
But I haven't been able to pin down exactly what causes this.
Sometimes the axes appear in front of the surface no matter
what I do, but other times they don't.  I suspect an 
un-initialized variable somewhere, but I haven't been able
to track it down.  A 100% reproducible test case would help.
But I've been working with the CVS code; maybe the issue
is more clear-cut in 4.2.

> Again, is this a bug, or am I using the commands
> incorrectly?

I think it's a bug, but it's a subtle one.

 
> (Version info below.)
> 
> Best,
> 
> 		Ph.
> 
> 
> 
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-- 
Ethan A Merritt
Biomolecular Structure Center
University of Washington, Seattle 98195-7742