Re: [Gnuplot-info] is painting with corners2color working incorrectly for Y axis?

[Norwid B. <nb...@ya...>]

Hello Yury,

in your approach 

> I have to use BOTH `samples` and `isosamples`, 
> set to the same value. The following produces 
> just what was intended:
> ```
> set terminal x11 ;
> set size square.
> set xrange [-3:4]; set yrange [-3:4];
> set samples 8 ; set isosamples 8
> sigma = 2.0;
> f(x,y) = (1/(2*pi*sigma**2)) * 
> exp(-(x*x+y*y)/(2*sigma**2)) ;
> set grid
> set pm3d map corners2color c1;.
> splot f(x,y)
> ```

the "tiles" are equidistant along (x,y) and the color levels appear to me
symmetric (like an axis C_\infty in molecular symmetry / point groups,
perpendicular to the drawing plane) around the central tile with an offset,
i.e. its centre is at (0.5,0.5) instead of exactly (0,0) you prefer.  I do
not know how to shift the array of tiles to account for this.  In addition, I
notice `set samples 8 ; set isosamples 8` is a rather "lucky combination" as
e.g., `set samples 9 ; set isosamples 9` or `set samples 7 ; set isosamples 7`
distort the symmetry of this intensity map which can be misleading.

Previously, my suggest was to increase the levels of `samples` / `isosamples`
to yield an offset no longer significant for the visual analysis of the 3D map.
Meanwhile, I read newly released gnuplot 6 provides an automatic `counterfill`
with a better visualization of the local extreme around (0,0) in the
projection worth to try as an alternative approach: 

```
set terminal x11 ;
set terminal qt;
set size square
set xrange [-3:4]; set yrange [-3:4];
set samples 100 ; set isosamples 100
sigma = 2.0;
f(x,y) = (1/(2*pi*sigma**2)) * exp(-(x*x+y*y)/(2*sigma**2)) ;
set grid

set contourfill auto 10
splot f(x,y) with contourfill
# set view map; replot  # uncomment for the static 2D projection
```

Credit for the inspiration is due to Lee Philips' [Gnuplot 6 comes with
pie](https://lwn.net/Articles/961003/) published by February 9, 2024.

Norwid