Re: [ gnuplot-Patches-1323515 ] Sort points in 3D before plotting

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

On Tuesday 11 October 2005 12:05 pm, Petr Mikulik wrote:
> >> The series of points can be  a time sequence, and there it
> >> would be useful to draw them (into a map) as they appear in
> >> the data file, without ordering.
> >
> > I do not understand this example. Could you explain what the
> > x, y, and z coordinates would be in this case?
> 
> The data will be drawn as a color map (set view map).
> x, y - coordinate
> z - colour
> 
> Example: data file contains several scans (through angles, for example) of 
> scattered intensity, the sample has been measured several times, and I want 
> to see the latest values -- thus the previous have to be hidden below the 
> latest data.

OK. I understand.
 
> (Or, one would have to be think that the z-coordinate is $0, not $3).

Yes, that would work:
  set view map
  plot "series" using 1:2:0:3 with linespoints palette

The sort is on $0, but the color is taken from column 3.
That works fine for "set view map", although I admit that it is a change
from previous behavior.

But it doesn't work to retrace curves in the general 3D case
(not "set view map").  So yes, I see that there must be some way to
toggle the sort on and off.

> The trouble of hidden3d is that it is a global filter, not an option for the 
> plot style. 

The property of being global is exactly what you need in order 
to do Z-ordering for multiplot datasets within the same plot.
Otherwise the later plots will always occlude the earlier ones.

 
> > I am not clear on how this would fit in with Johannes Zellner's
> > patch #1077726 "true depth ordering for pm3d plots".
> 
> Yes. It is reordering the facets (quadrangles) same way as you do here for 
> points. Both are useful for a nice visualization of surfaces.

But you could not mix them in the same graph unless they were both
moved into the global hidden3d code, right?


-- 
Ethan A Merritt       merritt@u.washington.edu
Biomolecular Structure Center
Mailstop 357742
University of Washington, Seattle, WA 98195