Re: Missing/invalid data points in PM3D

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

>    if (j == DF_UNDEFINED || j == DF_MISSING) {
>        cp->type = UNDEFINED;
>        continue;
>    }
>
> It seems clear to me that at least for gridded surfaces the
> "continue" statement should be replaced by a jump to
> come_here_if_undefined.  That does, in fact, fix the specific
> problem reported on the newsgroup.
>
> However, I am dubious about the affect this has on PM3D output.
> I tried replacing one of the data points in triangle.dat with a
> nonsense string, or with NaN, and issuing the commands
>
> 	splot 'triangle.dat' using 1:2:3 with pm3d
> 	splot 'triangle.dat' using ($1):($2):($3) with pm3d
>
> The results are odd, to say the least.
>
> What is supposed to happen if pm3d sees an invalid point?

You mean handling of points marked as UNDEFINED in routine pm3d_plot().

If any of the 4 corners to be drawn as a color quadrangle is undefined, then 
its drawing is skipped. It is the "continue" in the last occurence of 
"UNDEFINED" string in pm3d.c.

In pm3d.c, if you uncomment these blocks:
   /* debugging: print scan_array */
   /* debugging: this loop prints properties of all scans */

then all the scans&points gnuplot passes into the pm3d draw routine will be 
printed.

I see that in both cases of a NaN-changed triangle.dat:
  	splot 'triangle.dat' using 1:2:3 with pm3d
  	splot 'triangle.dat' using ($1):($2):($3) with pm3d

no undefined point comes into pm3d_plot() -- thus, they are missing. Then 
the scan with a NaN is 1 point shorter and thus qudrangles instead of 
rectangles for a grid topology are drawn behind that.

With your patch of plot3d.c, all scans have the number of points as 
intended. The rectangle(s) contaning a point with NaN are not drawn. This 
looks like to be what is expected, so I propose you commit the plot3d.c 
patch.

---
PM