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

[Petr M. <mi...@ph...>]

>> 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
line number in the file = this gives the z-order, which point is drawn the 
last

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.

I use this "overlapping" when measuring scattered intensity in regions of 
reciprocal space of a sample with and without absorber, and overlapping that 
part which has better statistics. If gnuplot sorts the data, that would 
destroy the image.

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

> the longer term plan should be to extend the category of
> plots handled by "set hidden3d".  In particular the hidden3d code
> could sort points and line segments even if there is no surface

The trouble of hidden3d is that it is a global filter, not an option for the 
plot style. Having the sort as an option, it would be more convenient.

> I am not clear on how this would fit in with Johannes Zellner's
> patch #1077726 "true depth ordering for pm3d plots".
> Have you looked at that patchset?

Yes. It is reordering the facets (quadrangles) same way as you do here for 
points. Both are useful for a nice visualization of surfaces. For "maps", it 
would bring processing artefacts to overlapping regions.

---
PM