[Gnuplot-info] How to disable grid-data mode with splot ?

[Francois M. <ma...@lp...>]

Dear Gnuploters,

I use the splot command with some data file for 3D rendering
with "wire" mode (no surfaces, facets ad the like).
My datafiles provides collections of vertexes (polylines) representing
the edges of 3D solid shapes managed by some external library.
This is particularly useful to check/visualize if some virtual geometry 
setup
is correct, helping to detect solid overlap...

Unfortunately, the splot driver regularly and automatically switches to 
'grid data' mode, adding annoying segments to connect some vertexes 
where I do not want to use this "isolines"
features. Reading the doc explains why it works lie, this:
<cite from="Gnuplot documentation">
If all datablocks contain the same number of points,
gnuplot will draw cross-isolines between datablocks, connecting 
corresponding points.
</cite>

Example: here I want to draw 2 parallel vertical segments AB and CD:
<pre>
gnuplot> splot '-' with line
0 0 0 # vertex A
0 0 1 # vertex B

1 0 0 # vertex C
1 0 1 # vertex D

e
</pre>
As both datablocks have 2 lines, the 'grid data' is activated
and it plots a vertical square ABDC in place of my only 2 segments!

For now I was not able to find a way (through a special option or 
command) that
would inhibit this feature and I am forced to add arbitrary vertexes to 
break
the  'grid data' feature:
<pre>
gnuplot> splot '-' with line
0 0 0   # vertex A
0 0 0.5 # trick: vertex 0.5*(A+B) is an additional mid-point for the 
first segment
0 0 1   # vertex B

1 0 0 # vertex C
1 0 1 # vertex D

e
</pre>
this restores my "2 segments" plot because datablocks don't have the
same number of vertexes.

I'd like to know if there is some kind of "unset grid data" command
or "splot 'a.data' index 0 nogriddata with lines" option ti inhibit
this feature.
If not it would be very useful to have it in gnuplot.
I just want to plot a collection of simple polylines with arbitrary 
number of vertexes, no
emulated grid-ed surfaces.

Many thanks for any help or hint.

fm
-- 
François Mauger